Crossfire fails emissions
Team Owner
Joined: Oct 2004
Posts: 46,940
Likes: 2
From: Diesel smoke Makes me horny
St. Jude Donor '05-'06-'07-'08
Originally Posted by Twin_Turbo
running too rich, check the exhaust system for leaks upstream of the o2 sensor, check ehaders for cracjs and leaks, also at the knuckle joint between headers and rest of the exhaust, check the AIR tubes, check valves and if the system operates properly (air to headers during open loop and to cat during closed, easy to see w/ aldl grounded and engine running,check engine light flashing indicates open loop if flashing fast = probing for O2 signal and slow for closed loop where light on - rich lambda >1 and off is lean, every crossign point is a cross count) Check O2 sensor, check TPS setting, check coolant temp sender and open/closed loop operation.
Check if oxydizing section is getting air feed from the feed pipe.
If all fails, dump some alcohol in the tank to pass the test.
Check if oxydizing section is getting air feed from the feed pipe.
If all fails, dump some alcohol in the tank to pass the test.
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by Twin_Turbo
what are the INT and BLM numbers?
INT = 128
BLM = 172
Warm at 2800 rpm in neutral:
INT = 122
BLM = 147
Forgive my ignorance but what do the INT and BLM represent. Still learning.
Only corrulation I've figured so far is that the car seems to intermittantly go into open loop after various combination of events. This corrisponds to a few seconds after the O2 voltage rising above approx .325 volts. Stays open loop until O2 voltage drops to just about exactly .300 volts and then goes closed loop. As long as the O2 voltage then stays below .325 or so, no matter what the throttle application, it stays in closed loop. However raised RPM's, or certain application of throttle tend to raise the O2 numbers as the mixture richens up, and when it gets to about .325, a few seconds later it goes open loop. I've seen the O2 voltage as high as .670 then returning to rpm to idle it starts to drop. When it reaches .300 volts, it then goes closed loop again. Closed loop O2 voltage reading settles at approx .230 at idle. While sitting there idling if the fan turns on or some other event the O2 voltage may rise above approx .325 and it goes open loop again. When whatever happens that it "settles" and the voltage starts dropping, it hits .300 and goes closed loop again.
So, I now know that smog issue was likely the fact that the system is running open loop often when it shouldn't be, and often at idle. However I'm still at a loss as to specifically why it's acting intermittantly or where I should look next.
Last input is that I did take the the car out for about a 20 minute drive and logged that trip. It didn't throw any codes w/in town and secondary highway driving. Hasn't thrown any codes for that matter since I cleared what was in there. (44 - lean exhaust) Just keeps going open loop at "it's pleasure".
So that is todays discoveries. Went from no hard info at all to flooded w/data that I still don't completely understand within a day. Perhaps at this learning rate and the continued input of the forum, I might actually get this figured out for repair this weekend. We shall see.
Thanks for your ongoing input!
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
The INT is the Integer, this is a sort of real time correction factor for the injector pulse width (injector open time) Think of it as this: _____|------|_ where the high part is the open time in a cycle, this is what the ECM adjusts to give more fuel. The pulsewidths are pre programmed in the prom as a baseline calibration and from the O2 sensor feedback (that's why it's called closed loop, it's a closed loop feedback system) hanges are made to this. The "learning" that is commonly referred to when an ECM makes changes is represented by the BLM, the block learn multiplier. The BLM is a long term correction factor, sort of a fine calibration of the prom code to long time input (actually it's not a number but a field of numbers, a matrix).
The BLM is stored in RAM (memory) whereas the INT is not.
Both BLM and INT are stored (int only w/ ign on) in a 16 cell matrix where each cell represents a field for certain engine load & rpm. What you see on the scanner is the cell that is representing the current conditions.
Think of it as this:
rpm
^
|13 14 15 16
|09 10 11 12
|05 06 07 08
|01 02 03 04
---------->
load
if ideal all cells are 128.
The BLM gives a long term correction factor on top of the prom code and has less influence % wise on the pulsewidth than the INT. The INT makes fast and large changes. From those numbers you can see the BLM is way above 128 that means the ECM is constantly adding more fuel than what it should for no correction (ideal), so the ECM is compensating for something and the ECM thinks it has "done it" w/ the BLM, there's no need to mess w/ the INT to change it even more, however at 2800 rpm you see it's pulling pulsewidth to lower the amount of fuel added by a reasonable bit. This is further confirmation of a false lean signal in the exhaust and it can be that this lean signal is not "consistent" over the rpm tange so that it doesn't exist or is as prominent at that rpm so the real time correction factor INT pulls pulsewidth. The BLM is sort of a average over a longer period if you will.
The INT is a CLOSED LOOP only thing, if you are not in closed loop it has no effect and the cell will display 128. All fields, BLM and INT run from 0 to 255.
The BLM, being stored in RAM also corrects during open loop. It adjusts the base prom calibration based on what has been learned while the system has been operating. However the BLM only "learns" in CLOSED loop mode, in open loop it has no feedback and is just enforcing it's adjustment on the prom codes since it's assumed that similar demands exist for rpm and load.
The BLM responds to the INT, not the oxygen signal..the INt responds to the oxygen signal. Think of the BLM as a delayed rsponse to the INT and is slow in catching up. Once the INT moves somewhere the blm will slowly creep towards it, so with the int constantly moving around the blm is always late to catch up but if the INT remains at a certain level for some tie the blm will catch up to that, the more the blm deviates to that the less adjustment is needed from the INT. The stored BLM will continuously adjust the fuel delivery, also after the engine has been shut down and restarted. This is why the ecm has to "learn" again after the voltage has been pulled from it or a critical change/repair has been made.
a blm of 172 is VERY high, that's about 40% increase over normal, very rich.
the .300 ish voltages are all lean, the crossover point is somewhere around .45V, that's about lambda = 1.
the sensor's range is from .1 to .9 roughly. The sensor will start to produce it's own voltage (yes!!! it produces the voltage itself!!!) from the chemical potential (concentration) difference of oxygen in outside air and exhaust gas...the nature is that all concentration differences want to cancel out, like osmosis, and the air molecules want to go through the zirconia element and mix into the exhaust gas to even it out, of course there's no way that enough can get through but this does create a chemical potential, a voltage. That's why the sensor needs to warmp up, cooler and the zirconia isn't permeable for oxygen molecules. Low sensor voltage = lean exhaust (as in there's more O2 in the exhaust than would have been if all was burned in the ideal 14.7:1 burning, the chemical potential is lower)
During open loop the o2 sensor is constantly probed for voltage (the fast flashing), if the voltage goes a little above .45 and drops again then it's assumed that it's warm, then 2 more criteria need to have been met, a certain amount of time and warm coolant, that's why the CTS is so important (and therefore the thermostat!). .45V is actually a sort of "black hole" in the whole range as this voltage is almost impossible to get at with the mixture constantly changing over from lean to rich and to lean again, lambda =1 is never set, it's always dynamically hovering around it. This is because of the way the system works.
Here's a brief overview of how it works..copied from my website
The ECM controls the injection system, it fuctions in either one of 3 different modes:
Shutdown Mode.. When the ignition is off for 2 or more seconds. Only the RAM (trouble codes) and the BLM remain powered.
Startup Mode. When engine is cranked. Timing is locked at initial starup and air/fuel ratio is enriched. This mode is on for about two seconds after starting to ensure the engine will continue to run.
Running mode devided in:
CLOSED LOOP. The red arrow doesn't indicate a signal, it's an event. Due to the more/less pulsing of the injectors a rich/lean condition will be observed and the ECM will compensate for this.
In closed loop mode the ECM has 2 differend modes;
Enleanment Mode When the throttle is closed.
Enrichment Mode.
At wide open throttle.
High engine load.
High engine RPM.
Overheating engine. (the cold fuel is a great contributor to engine cooling)
The ECM is normally in enleanment mode, it constantly lowers fuel addition. When the oxygen sensor detects a lean condition enrichment mdode is entered untill the oxygen sensor doesn't sense a lean condition anymore. Than enleanment is entered again. This (theoretic) gaurantees an "ideal" air/fuel ratio.
OPEN LOOP.
Fuel cutoff Mode. When the throttle is closed and the MAP sensor notices a negative load (deceleration) untill about 1500 RPM..
Clear flood Mode. When throttle is depressed more than 80% while cranking. Injectors are turned off or air/fuel ratio is lowered to 20:1.
Limp Home Mode. When there is major trouble with any of the critical sensors/actuators.
The ECM monitors different sensors and controls the injectors and actuators to respond to changes/demands.
The different sensors and actuators are:
The Oxygen
sensor is the only sensor on the car that creates it's own voltage and has therefore only one wire coming from it. It's actually a chemical voltage generator, based on the potential difference between the oxygen rich condition in outside air and the lean condition in exhaust gas.. When it's at it's operating temperature of about 600ºFahrenheit it will produce a Voltage ranging from 100 to 900 mV. At operating temperatures the sensor will respond to changes in the oxygen content in the exhaust gasses. It creates a potential difference between the "clean" oxygen rich outside air and the oxygen poor exhaust gas. The voltage potential is developed due to chemical imbalance between the two oxygen concentrations. When the voltage is low (oxygen levels in exhaust high) the ECM will assume the engine is running lean and thus enter the enrichment mode. Lean conditions usually produce voltages lower than 450mV, rich will be over 450mV. As you can see there is a very critical value for "ideal" air-fuel ratio. This is done to ensure that the engine never runs very lean/rich. This way a nearly ideal air fuel ratio is always obtained, the engine never gets the chance to run off this point by far without the ECM noticing it.
Due to the nature of the oxygen sensor it has a hard time distinguishing between a perfect and a rich running engine, when all oxygen is burnt the mixture can be ideal or rich. The oxygen sensor doesn't recognise surplus (unburnt) fuel in the exhaust. Therefore the ECM will always assume the engine is running rich unless it notices a lean condition.
The Tach Signal The Tach signal is used to synchronise and sometimes (WOT) sequence the injectors. At very high engine RPM the ECM always enters enrichment mode. The TPS is actually a three wire potentiometer. It's got a 5V reference sent to it by the ECM. The TPS is grounded through the ECM. The 5V is lowered to a different voltage through the potentiometer (read variable resistor) When at no throttle the resistance is lowest and the voltage is also lowest (normalle set to 0.525V ±0.025) When at full throttle the resistance between the 5V and the ground is highest (theoretical infinity) and the potential difference (voltage) will be 5V.
The Idle Air Control valve or IAC (stepper motor)
The IAC is a motorised plunger that regulates the idle speed of the engine by regulating the incoming airflow. The IAC has 256 positions. At normal idle it's somwhere around position 20. When full throttle is applied the IAC valve completely opens.
The EST retards timing when the knock sensor (a sort of microphone) notices detonation. Normal spark timing is controlled by the EST, commanded by the ECM.
The EGR or Exhaust Gas Recirculation
EGR is a method to decrease emissions by venting exhaust gas into the intake (about 7% of the intake volume is rendered "useless" due to this). It also decreases detonation due to the uncombustable (inert) exhaust gas. The EGR position is ECM controlled via the EGR position control solenoid. This is a solenoid that regulates vacuum to the EGR valve thus opening/closing it.
The AIR system or Air Injection Reactor
The A.I.R system consists of an AIR pump or just SMOG pump, that pumps fresh air into the headers/catalytic converter. When the engine is in closed loop air flows into the headers (and cylinder head exhaust ports) to speed up O2 sensor warmup. When the engine is running in closed loop air is pumped into the catalytic converter to speed up the chemical reactions taking place there. Also during deceleration the air is vented to the atmosphere to reduce detonation in the exhaust. The route the air travels is regulated by a control solenoid (that is ECM controlled)
The TCC or Torque Converter Clutch (lockup converter)
The TCC is engaged when the car is travelling at about 30mph at relatively light load and in a high gear and when a relatively steady signal is observed from the TPS (steady throttle) This is done to maximize fuel efficiency.
AC compressor clutch
When the Air Conditioning compressor clutch is on the ECM increases the RPM at idle to account for the increased load.
The Auxiliary cooling fan
The Cooling Fan is engaged when the ECM detects a high signal from the coolant temperature switch. On the Cross- Fire system the auxiliary fan is NOT ECM controlled
CTS or Coolant Temperature sender
The Coolant Temperature sensor on the manifold sends a signal to the ECM. The one on the drivers side cylinder head goes to the temperature gauge, the passenger side one controls the auxiliary fan.
The MAP sensor or Manifold Absolute Pressure sensor
The MAP monitors the manifold pressure and is an indicator for engine load. Also the ECM calculates the quantity of incoming air from the signal of this sensor.
Do you have a stock exhaust under there???
Are you running a 160F stat????
Normally a system representing this kind of data would lead one to believe that there's a vac. leak, however since your exhaust sniffs clearly indicate a rich condition check the exhaust and air system, never hurts to check for vac leaks however, also check the TBs for worn housings where the throttle shafts go in (steel on bare aluminium) and play there.
The BLM is stored in RAM (memory) whereas the INT is not.
Both BLM and INT are stored (int only w/ ign on) in a 16 cell matrix where each cell represents a field for certain engine load & rpm. What you see on the scanner is the cell that is representing the current conditions.
Think of it as this:
rpm
^
|13 14 15 16
|09 10 11 12
|05 06 07 08
|01 02 03 04
---------->
load
if ideal all cells are 128.
The BLM gives a long term correction factor on top of the prom code and has less influence % wise on the pulsewidth than the INT. The INT makes fast and large changes. From those numbers you can see the BLM is way above 128 that means the ECM is constantly adding more fuel than what it should for no correction (ideal), so the ECM is compensating for something and the ECM thinks it has "done it" w/ the BLM, there's no need to mess w/ the INT to change it even more, however at 2800 rpm you see it's pulling pulsewidth to lower the amount of fuel added by a reasonable bit. This is further confirmation of a false lean signal in the exhaust and it can be that this lean signal is not "consistent" over the rpm tange so that it doesn't exist or is as prominent at that rpm so the real time correction factor INT pulls pulsewidth. The BLM is sort of a average over a longer period if you will.
The INT is a CLOSED LOOP only thing, if you are not in closed loop it has no effect and the cell will display 128. All fields, BLM and INT run from 0 to 255.
The BLM, being stored in RAM also corrects during open loop. It adjusts the base prom calibration based on what has been learned while the system has been operating. However the BLM only "learns" in CLOSED loop mode, in open loop it has no feedback and is just enforcing it's adjustment on the prom codes since it's assumed that similar demands exist for rpm and load.
The BLM responds to the INT, not the oxygen signal..the INt responds to the oxygen signal. Think of the BLM as a delayed rsponse to the INT and is slow in catching up. Once the INT moves somewhere the blm will slowly creep towards it, so with the int constantly moving around the blm is always late to catch up but if the INT remains at a certain level for some tie the blm will catch up to that, the more the blm deviates to that the less adjustment is needed from the INT. The stored BLM will continuously adjust the fuel delivery, also after the engine has been shut down and restarted. This is why the ecm has to "learn" again after the voltage has been pulled from it or a critical change/repair has been made.
a blm of 172 is VERY high, that's about 40% increase over normal, very rich.
the .300 ish voltages are all lean, the crossover point is somewhere around .45V, that's about lambda = 1.
the sensor's range is from .1 to .9 roughly. The sensor will start to produce it's own voltage (yes!!! it produces the voltage itself!!!) from the chemical potential (concentration) difference of oxygen in outside air and exhaust gas...the nature is that all concentration differences want to cancel out, like osmosis, and the air molecules want to go through the zirconia element and mix into the exhaust gas to even it out, of course there's no way that enough can get through but this does create a chemical potential, a voltage. That's why the sensor needs to warmp up, cooler and the zirconia isn't permeable for oxygen molecules. Low sensor voltage = lean exhaust (as in there's more O2 in the exhaust than would have been if all was burned in the ideal 14.7:1 burning, the chemical potential is lower)
During open loop the o2 sensor is constantly probed for voltage (the fast flashing), if the voltage goes a little above .45 and drops again then it's assumed that it's warm, then 2 more criteria need to have been met, a certain amount of time and warm coolant, that's why the CTS is so important (and therefore the thermostat!). .45V is actually a sort of "black hole" in the whole range as this voltage is almost impossible to get at with the mixture constantly changing over from lean to rich and to lean again, lambda =1 is never set, it's always dynamically hovering around it. This is because of the way the system works.
Here's a brief overview of how it works..copied from my website
The ECM controls the injection system, it fuctions in either one of 3 different modes:
Shutdown Mode.. When the ignition is off for 2 or more seconds. Only the RAM (trouble codes) and the BLM remain powered.
Startup Mode. When engine is cranked. Timing is locked at initial starup and air/fuel ratio is enriched. This mode is on for about two seconds after starting to ensure the engine will continue to run.
Running mode devided in:
CLOSED LOOP. The red arrow doesn't indicate a signal, it's an event. Due to the more/less pulsing of the injectors a rich/lean condition will be observed and the ECM will compensate for this.
In closed loop mode the ECM has 2 differend modes;
Enleanment Mode When the throttle is closed.
Enrichment Mode.
At wide open throttle.
High engine load.
High engine RPM.
Overheating engine. (the cold fuel is a great contributor to engine cooling)
The ECM is normally in enleanment mode, it constantly lowers fuel addition. When the oxygen sensor detects a lean condition enrichment mdode is entered untill the oxygen sensor doesn't sense a lean condition anymore. Than enleanment is entered again. This (theoretic) gaurantees an "ideal" air/fuel ratio.
OPEN LOOP.
Fuel cutoff Mode. When the throttle is closed and the MAP sensor notices a negative load (deceleration) untill about 1500 RPM..
Clear flood Mode. When throttle is depressed more than 80% while cranking. Injectors are turned off or air/fuel ratio is lowered to 20:1.
Limp Home Mode. When there is major trouble with any of the critical sensors/actuators.
The ECM monitors different sensors and controls the injectors and actuators to respond to changes/demands.
The different sensors and actuators are:
The Oxygen
sensor is the only sensor on the car that creates it's own voltage and has therefore only one wire coming from it. It's actually a chemical voltage generator, based on the potential difference between the oxygen rich condition in outside air and the lean condition in exhaust gas.. When it's at it's operating temperature of about 600ºFahrenheit it will produce a Voltage ranging from 100 to 900 mV. At operating temperatures the sensor will respond to changes in the oxygen content in the exhaust gasses. It creates a potential difference between the "clean" oxygen rich outside air and the oxygen poor exhaust gas. The voltage potential is developed due to chemical imbalance between the two oxygen concentrations. When the voltage is low (oxygen levels in exhaust high) the ECM will assume the engine is running lean and thus enter the enrichment mode. Lean conditions usually produce voltages lower than 450mV, rich will be over 450mV. As you can see there is a very critical value for "ideal" air-fuel ratio. This is done to ensure that the engine never runs very lean/rich. This way a nearly ideal air fuel ratio is always obtained, the engine never gets the chance to run off this point by far without the ECM noticing it.
Due to the nature of the oxygen sensor it has a hard time distinguishing between a perfect and a rich running engine, when all oxygen is burnt the mixture can be ideal or rich. The oxygen sensor doesn't recognise surplus (unburnt) fuel in the exhaust. Therefore the ECM will always assume the engine is running rich unless it notices a lean condition.
The Tach Signal The Tach signal is used to synchronise and sometimes (WOT) sequence the injectors. At very high engine RPM the ECM always enters enrichment mode. The TPS is actually a three wire potentiometer. It's got a 5V reference sent to it by the ECM. The TPS is grounded through the ECM. The 5V is lowered to a different voltage through the potentiometer (read variable resistor) When at no throttle the resistance is lowest and the voltage is also lowest (normalle set to 0.525V ±0.025) When at full throttle the resistance between the 5V and the ground is highest (theoretical infinity) and the potential difference (voltage) will be 5V.
The Idle Air Control valve or IAC (stepper motor)
The IAC is a motorised plunger that regulates the idle speed of the engine by regulating the incoming airflow. The IAC has 256 positions. At normal idle it's somwhere around position 20. When full throttle is applied the IAC valve completely opens.
The EST retards timing when the knock sensor (a sort of microphone) notices detonation. Normal spark timing is controlled by the EST, commanded by the ECM.
The EGR or Exhaust Gas Recirculation
EGR is a method to decrease emissions by venting exhaust gas into the intake (about 7% of the intake volume is rendered "useless" due to this). It also decreases detonation due to the uncombustable (inert) exhaust gas. The EGR position is ECM controlled via the EGR position control solenoid. This is a solenoid that regulates vacuum to the EGR valve thus opening/closing it.
The AIR system or Air Injection Reactor
The A.I.R system consists of an AIR pump or just SMOG pump, that pumps fresh air into the headers/catalytic converter. When the engine is in closed loop air flows into the headers (and cylinder head exhaust ports) to speed up O2 sensor warmup. When the engine is running in closed loop air is pumped into the catalytic converter to speed up the chemical reactions taking place there. Also during deceleration the air is vented to the atmosphere to reduce detonation in the exhaust. The route the air travels is regulated by a control solenoid (that is ECM controlled)
The TCC or Torque Converter Clutch (lockup converter)
The TCC is engaged when the car is travelling at about 30mph at relatively light load and in a high gear and when a relatively steady signal is observed from the TPS (steady throttle) This is done to maximize fuel efficiency.
AC compressor clutch
When the Air Conditioning compressor clutch is on the ECM increases the RPM at idle to account for the increased load.
The Auxiliary cooling fan
The Cooling Fan is engaged when the ECM detects a high signal from the coolant temperature switch. On the Cross- Fire system the auxiliary fan is NOT ECM controlled
CTS or Coolant Temperature sender
The Coolant Temperature sensor on the manifold sends a signal to the ECM. The one on the drivers side cylinder head goes to the temperature gauge, the passenger side one controls the auxiliary fan.
The MAP sensor or Manifold Absolute Pressure sensor
The MAP monitors the manifold pressure and is an indicator for engine load. Also the ECM calculates the quantity of incoming air from the signal of this sensor.
Do you have a stock exhaust under there???
Are you running a 160F stat????
Normally a system representing this kind of data would lead one to believe that there's a vac. leak, however since your exhaust sniffs clearly indicate a rich condition check the exhaust and air system, never hurts to check for vac leaks however, also check the TBs for worn housings where the throttle shafts go in (steel on bare aluminium) and play there.
Last edited by Twin_Turbo; Dec 1, 2005 at 06:34 AM.
Drifting
Joined: Sep 2004
Posts: 1,270
Likes: 4
From: Celeste Texas
Proffessor TT,
I've been working on cars and planes for a lot of years now and I used to think I was pretty smart. After reading that I just hope that I don't fail your class. If you ever make it to Texas, I have a Steak dinner and a cold beer waiting for you.
Bill
I've been working on cars and planes for a lot of years now and I used to think I was pretty smart. After reading that I just hope that I don't fail your class. If you ever make it to Texas, I have a Steak dinner and a cold beer waiting for you.
Bill
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
You'll also find more context (not that you need any beyond twin turbo's explanation) for BLM and INT if you modernize BLM to long term fuel trim and INT to short term fuel trim. They show up as percentages in the datastream.
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by Twin_Turbo
........Do you have a stock exhaust under there???
Are you running a 160F stat????
Normally a system representing this kind of data would lead one to believe that there's a vac. leak, however since your exhaust sniffs clearly indicate a rich condition check the exhaust and air system, never hurts to check for vac leaks however, also check the TBs for worn housings where the throttle shafts go in (steel on bare aluminium) and play there.
Are you running a 160F stat????
Normally a system representing this kind of data would lead one to believe that there's a vac. leak, however since your exhaust sniffs clearly indicate a rich condition check the exhaust and air system, never hurts to check for vac leaks however, also check the TBs for worn housings where the throttle shafts go in (steel on bare aluminium) and play there.
Exhaust is stock-ish. Standard/stock layout but I'm sure the parts have been replaced sometime over the past 22+ years. I've only owned the car since this past March so I don't know it's history very far back. I did also note yesterday that the cat had a rubber hose w/standard hose clamps connecting it to the air feed line from the pump/valve. In reading the manual last night I see that there was a hard line and flaired type connection all the way to the original cat. So I'm now assuming the cat has been changed to a more generic version sometime along the way. I didn't observe any obvious leaks at the hose, however I would need to check closer to be sure. I only had the car jacked up a few inches, just enough to get my head and arm under there.
Thermostat is a Motorad failsafe 195 degree unit. It was checked stovetop before installation, which was this past spring. Haven't checked it since but it appears to be doing what it should as the car always warms up to about 195 degrees before dropping slightly and then up from there. I'm assuming the slight/short drop is the thermostat opening.
I am trying to refrain from doing any disassembly until the weekend and it sounds like this is the next step. Can't check the air control and check valve w/o some disassembly. Will get a closer look at the exhaust system, vacuum lines, AIR valves and feed lines, etc then.
As another side note, I previously had a 'will only return to idle intermittantly' issue. Stayed at 1000-1200 rpm much of the time. After removing and cleaning the IAC's, the issue was much better but it's still slow to return to idle some of the time. Guess a closer look around the TB shafts is in order as this was suggested as one possible point of failure for that issue. Assuming there is an issue w/the shafts, is there any "easy" repair for this beyond drilling and adding a bushing?
Not sure how much I'm going to be able to do today but if I do get a few free moments I'm sure to be out there poking around some more. Will keep you posted.
Again many thanks for all the input!
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by gerry72
You'll also find more context (not that you need any beyond twin turbo's explanation) for BLM and INT if you modernize BLM to long term fuel trim and INT to short term fuel trim. They show up as percentages in the datastream.
Will take a closer look when I next have it hooked up. I do remember seeing something about fuel trim.BTW, I do have a couple logged text files and one I converted to Excel for ease of reading and eliminating the unused data. If anyone wants a copy for evaluation, I'd be glad to e-mail it to them. FWIW.
Thanks again.
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Pro
Joined: Nov 2004
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From: Frisco TX
Originally Posted by ACECO
I did also note yesterday that the cat had a rubber hose w/standard hose clamps connecting it to the air feed line from the pump/valve. In reading the manual last night I see that there was a hard line and flaired type connection all the way to the original cat. So I'm now assuming the cat has been changed to a more generic version sometime along the way.
Is there a chance that this "New" cat is just a gutted old cat? I have no idea what would happen to the reading on the system if it was just a gutted shell.
Does the 84 have the dreaded pre-cats like the 89s? I have heard that they go bad often.
Tim
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Originally Posted by RocketSapp
Is there a chance that this "New" cat is just a gutted old cat? I have no idea what would happen to the reading on the system if it was just a gutted shell.
Does the 84 have the dreaded pre-cats like the 89s? I have heard that they go bad often.
Tim
Does the 84 have the dreaded pre-cats like the 89s? I have heard that they go bad often.
Tim
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by RocketSapp
Is there a chance that this "New" cat is just a gutted old cat? I have no idea what would happen to the reading on the system if it was just a gutted shell.
Does the 84 have the dreaded pre-cats like the 89s? I have heard that they go bad often.
Tim
Does the 84 have the dreaded pre-cats like the 89s? I have heard that they go bad often.
Tim
In feeling/squeezing the hose it appears that the cat has a typical "nub" at the end of the AIR input line so I suspect it is a generic replacement vs a cut off GM version. No pre cats on an 84. Just the one in the center where the dual front pipes meet and the rear duals start from.
Thanks to all for the continued input.
Pro
Joined: Nov 2004
Posts: 677
Likes: 0
From: Frisco TX
Originally Posted by ACECO
I suppose this is possible but if I were to gut the cat I wouldn't have bothered cutting off the male fitting on the AIR feed line, removing the female connector block on the cat and pipeing it together with a piece of hose. I would have just put it back together as it was. Of course that is unless I couldn't get the fitting apart in the first place and just cut it out of line. I guess anything is possible.
In some states they only look to see if you have it... I am assuming they wanted to make it look like everything was stock. Depending on where the car has been, they might have been going for a look and feel.
Tim
Tim
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Quick update.
After describing the issue and speaking w/an old friend who has been a mechanic for 25+ years and getting his feedback, I decided to just "throw an O2 sensor at it and see what changes". While he has no direct crossfire experience, he said that he has seen O2 sensors do some funny stuff and for a $20 sensor, just change it. So I did.
Hooked up the laptop and WinALDL and checked it out. The new O2 sensor is much more responsive voltage wise and seems to jump from lean to rich numbers quite quickly. The old one responded quite slowly and would have to gradually climb or fall from one end to the other. This one just jumps from a .77 reading to a .20 reading. I still believe something is wrong and there is more here than just the O2 sensor issue, but apparently this was a good start. Of course I am assuming the O2 sensor should respond quickly and that jumping from rich directly to lean numbers while at a steady 1800 or so RPM in neutral is not normal. Anyone please correct me if I'm wrong on either of these assumptions. We all know what happens when we assume.
So i'm waiting for the LT batts to recharge but then will take it out for a ride and see what data I can collect w/the new O2 sensor. However in about 5-7 minutes of driveway running, I so far was unable to get it to go open loop. It did jump around from lean to rich, but no open loop so thats a good thing. Now I'll have to see why the closed loop is working so hard to find a happy medium. Vacuum or air leak somewhere is seeming to be a better and better bet. But we will see. Oh yes, and no codes thrown yet either.
Off to further troubleshooting. Wish me luck!
After describing the issue and speaking w/an old friend who has been a mechanic for 25+ years and getting his feedback, I decided to just "throw an O2 sensor at it and see what changes". While he has no direct crossfire experience, he said that he has seen O2 sensors do some funny stuff and for a $20 sensor, just change it. So I did.
Hooked up the laptop and WinALDL and checked it out. The new O2 sensor is much more responsive voltage wise and seems to jump from lean to rich numbers quite quickly. The old one responded quite slowly and would have to gradually climb or fall from one end to the other. This one just jumps from a .77 reading to a .20 reading. I still believe something is wrong and there is more here than just the O2 sensor issue, but apparently this was a good start. Of course I am assuming the O2 sensor should respond quickly and that jumping from rich directly to lean numbers while at a steady 1800 or so RPM in neutral is not normal. Anyone please correct me if I'm wrong on either of these assumptions. We all know what happens when we assume.
So i'm waiting for the LT batts to recharge but then will take it out for a ride and see what data I can collect w/the new O2 sensor. However in about 5-7 minutes of driveway running, I so far was unable to get it to go open loop. It did jump around from lean to rich, but no open loop so thats a good thing. Now I'll have to see why the closed loop is working so hard to find a happy medium. Vacuum or air leak somewhere is seeming to be a better and better bet. But we will see. Oh yes, and no codes thrown yet either.
Off to further troubleshooting. Wish me luck!
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
A good sensor will swing the range at least six times per second.
You can see a vacuum leak in the fuel trim. It will show up as a long term fuel trim (LTFT) consistently over -20 percent and a short term fuel trim (STFT) near peak of -99 percent. The reason for this is that the computer is trying to bring the LTFT to an optimal zero and keeps trying to increase the pulse width to add more fuel. The unmetered air makes it very difficult to do this and the bigger the leak, the bigger the trim percentages.
In order to get a good baseline reading following replacement of the O2 sensor, you'll want to unhook the battery for about 10 minutes, then hook it back up. This clears the keep alive memory and allow the fuel trim to reference base fuel maps. It will eventually find the correct map in the LTFT, but stopping the KAM and forcing it to start with base maps means you won't be confusing the data stream output correcting itself as an ineffective repair.
You can see a vacuum leak in the fuel trim. It will show up as a long term fuel trim (LTFT) consistently over -20 percent and a short term fuel trim (STFT) near peak of -99 percent. The reason for this is that the computer is trying to bring the LTFT to an optimal zero and keeps trying to increase the pulse width to add more fuel. The unmetered air makes it very difficult to do this and the bigger the leak, the bigger the trim percentages.
In order to get a good baseline reading following replacement of the O2 sensor, you'll want to unhook the battery for about 10 minutes, then hook it back up. This clears the keep alive memory and allow the fuel trim to reference base fuel maps. It will eventually find the correct map in the LTFT, but stopping the KAM and forcing it to start with base maps means you won't be confusing the data stream output correcting itself as an ineffective repair.
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Greetings all,
Sorry for the delay in reporting back but between a stubborn server job, the first snow of the season and everything else this time of year, I only today got back for reinspection. The car passed this time w/the following results:
Item------Limit-----1st Try----After O2 Sensor
------------------------------------------------
NOx------1184------182-----------429
HC--------157-------214-----------64
CO--------.88-------5.32----------0.04
So apparently the lazy/slow reacting old O2 sensor was good enough to keep the car from throwing a O2 sensor code, but still misfunctioning enough to allow the ECM to intermittantly (and often) drop back into the open loop/very rich mode.
I want to thank everyone who chimed in for their input. I very much appreciate it! And especially to Twin_Turbo for pointing me towards WinALDL and also taking the time to look at my log files. That was a real help!
Here's to two more years before I have to deal w/this again.
Happy Holidays To All!
Sorry for the delay in reporting back but between a stubborn server job, the first snow of the season and everything else this time of year, I only today got back for reinspection. The car passed this time w/the following results:
Item------Limit-----1st Try----After O2 Sensor
------------------------------------------------
NOx------1184------182-----------429
HC--------157-------214-----------64
CO--------.88-------5.32----------0.04
So apparently the lazy/slow reacting old O2 sensor was good enough to keep the car from throwing a O2 sensor code, but still misfunctioning enough to allow the ECM to intermittantly (and often) drop back into the open loop/very rich mode.
I want to thank everyone who chimed in for their input. I very much appreciate it!
And especially to Twin_Turbo for pointing me towards WinALDL and also taking the time to look at my log files. That was a real help! Here's to two more years before I have to deal w/this again.
Happy Holidays To All!
