To not throw parts at it
01-01-2019, 09:53 PM
#22
Team Owner
IF the ECM is trying to enrich the engine, the pulse width will be longer and more fuel sprayed into the engine. So if you should have 1.5 ms at say 70 degrees, it could tell you the ECM is trying to enrich the running if you have 2 ms of pulse width. It tells you how long the injectors are "firing" or opening. So for instance, when I had the driver side injector bank fail, the ECM saw the O2 sensor reading lean so it tried to enrich the motor by dumping in more fuel. When it didn't see the change, even more fuel till it couldn't adjust anymore. Fixed it and the pulse width dropped back to 1.4 from 2.8.
01-02-2019, 01:10 AM
#23
Race Director
I really can't understand why you are so reluctant to buy or borrow a scanner. You're willing to buy parts hoping you'll hit a bullseye while a scanner can point you in the right direction. Oh well, it's your car. By the way, temperature sensors don't have fuses.
01-02-2019, 10:57 AM
#24
Drifting
Thread Starter
Not here to start any fights and very grateful for everyone for the input.
01-02-2019, 02:28 PM
#26
Drifting
Thread Starter
If you are referring to a Volt/OHM meter I actually found that the one I have is screwed up so will be picking up a new one this week. Since I don't have the FSM I ordered yet and wont have time to even dig into the current issue until sometime this weekend at the earliest not too concerned at the moment. I am a bit pissed because the last weekend and new years day were warm enough for me to get to drive time in and work on a rattle that seems to be in the dash and this new issue screwed all that up.
01-02-2019, 04:03 PM
#27
Safety Car
Hello again "CorvetteRules" It is good to see that you are still working on getting your Corvette to be ready for fun! I hope that you and yours all had a wonderful Christmas and a Happy Start of the New Year!
Back to Corvettes, you did the right thing getting the original Factory Service Manuals for your year, these will help you understand more of the weird lingo we use talking about the engines. There are so many abbreviations that even I have to look them up once in a while.
Pulse Width Modulation is a term that refers to how the power is supplied to the component. I have a controller in my C3 that controls the Electric Fuel Pump I am using in that car. Instead of a steady supply of a solid 12 Vdc going to the pump it sends it in little tiny pulses, at low speeds it simply sends shorter Pulses allowing the Fuel pump less power, when I am going wide open throttle it sends longer pulses of 12 Vdc to make the pump keep up with the demand. The beauty is that when I am idling the fuel pump is barely doing anything and is very quiet and as the engine requires more fuel it simply sends more fuel to keep up with my engine's demands. I also have a Cooling fan controller that uses the PWM method, when the fans start running they come on at 50% power and slowly ramp up at whatever speed you choose. PWM is used more and more today and on a lot of things. Using PWM on my cooling system when you have a roughly 45 amp load for the two fans and when they kicked on before the lights dimmed and it was spiking my charging system. Now the fans come on and there is no spike as they are being operated at 50% power, PWM is a better way of controlling the speed of things like cooling fans and fuel pumps and even fuel injectors.
To help you understand the some of fuel system a bit better I will try to explain how it does "what it does". When the ignition key is in the "Run" position all of the injectors will all be supplied with 12 Vdc at one of the two terminals on the injectors. When the engine is running the computer supplies a Ground Signal to the injector allowing it inject the fuel. The length of the (0 Vdc) pulse (in milliseconds) determines "How much fuel" is injected. The injectors in my C4 are 24 Lb Bosch Injectors and they deliver 24 lbs of gasoline an hour running wide open. The computer in the C4's (with the L98) need to have roughly 42 pounds of fuel pressure and the injectors are fired in batches of four at a time and the injectors fire twice for every ignition cycle. The ECM is calculating how much gas to inject knowing the size of the injectors, the fuel pressure and the cars demand. It is kind of out of date but it works well if all the sensors are supplying the engine with accurate data within the limits.
If your CTS is sending a signal that it is 10* F and it is actually 70* F outside the car will try to start thinking it need extra fuel to compensate for the colder weather. If the CTS thinks it is 250* then it will try a hot start which might not work for your conditions. It is very important to be sure that all the sensors are in working condition before you attempt to fix anything else. I hope I did not over simplify the way the fuel injection systems works, if I did there will be somebody out there who will correct me if I am mistaken. Now you should understand why you can't just put bigger injectors in the car without changing several other functions. Believe it or not lots of people think they just need Bigger injectors to make more power...not.
Add another thing to your list of "things to check", if the car is starting and running properly and acts up when warm I would also check your Oxygen sensor for proper output voltage. This would show up on a scanner but when the O2 fails it does not always set off a Check Engine Light if it is in the process of failing. If the O2 is not working properly the engine will not run or run very poorly after it transitions to "Closed Loop".
The EGR system on my car had failed and it only affected the idle quality and I never would have known about it until the car failed the Emissions test here in Virginia. The NOX goes way up when the EGR fails. On my 1988 C4 the EGR failed because the EGR Vacuum Solenoid failed. The EGR's Vacuum Solenoid is located near the thermostat housing on the drivers side. When I bought the car the hoses were in terrible shape and the EGR Vacuum Solenoid was not getting vacuum, I trimmed roughly 1" from the ends but the lines continue to break down until all were replaced. If the EGR system is frozen and non-functional it too will affect your idle when the engine is warmed up.
I hope that this helps a bit! The experience that is represented here on the Corvette Forum is really incredible. There are so many fellow Corvette Enthusiasts out here anxious to help resolve your issues with your Corvette!
Back to Corvettes, you did the right thing getting the original Factory Service Manuals for your year, these will help you understand more of the weird lingo we use talking about the engines. There are so many abbreviations that even I have to look them up once in a while.
Pulse Width Modulation is a term that refers to how the power is supplied to the component. I have a controller in my C3 that controls the Electric Fuel Pump I am using in that car. Instead of a steady supply of a solid 12 Vdc going to the pump it sends it in little tiny pulses, at low speeds it simply sends shorter Pulses allowing the Fuel pump less power, when I am going wide open throttle it sends longer pulses of 12 Vdc to make the pump keep up with the demand. The beauty is that when I am idling the fuel pump is barely doing anything and is very quiet and as the engine requires more fuel it simply sends more fuel to keep up with my engine's demands. I also have a Cooling fan controller that uses the PWM method, when the fans start running they come on at 50% power and slowly ramp up at whatever speed you choose. PWM is used more and more today and on a lot of things. Using PWM on my cooling system when you have a roughly 45 amp load for the two fans and when they kicked on before the lights dimmed and it was spiking my charging system. Now the fans come on and there is no spike as they are being operated at 50% power, PWM is a better way of controlling the speed of things like cooling fans and fuel pumps and even fuel injectors.
To help you understand the some of fuel system a bit better I will try to explain how it does "what it does". When the ignition key is in the "Run" position all of the injectors will all be supplied with 12 Vdc at one of the two terminals on the injectors. When the engine is running the computer supplies a Ground Signal to the injector allowing it inject the fuel. The length of the (0 Vdc) pulse (in milliseconds) determines "How much fuel" is injected. The injectors in my C4 are 24 Lb Bosch Injectors and they deliver 24 lbs of gasoline an hour running wide open. The computer in the C4's (with the L98) need to have roughly 42 pounds of fuel pressure and the injectors are fired in batches of four at a time and the injectors fire twice for every ignition cycle. The ECM is calculating how much gas to inject knowing the size of the injectors, the fuel pressure and the cars demand. It is kind of out of date but it works well if all the sensors are supplying the engine with accurate data within the limits.
If your CTS is sending a signal that it is 10* F and it is actually 70* F outside the car will try to start thinking it need extra fuel to compensate for the colder weather. If the CTS thinks it is 250* then it will try a hot start which might not work for your conditions. It is very important to be sure that all the sensors are in working condition before you attempt to fix anything else. I hope I did not over simplify the way the fuel injection systems works, if I did there will be somebody out there who will correct me if I am mistaken. Now you should understand why you can't just put bigger injectors in the car without changing several other functions. Believe it or not lots of people think they just need Bigger injectors to make more power...not.
Add another thing to your list of "things to check", if the car is starting and running properly and acts up when warm I would also check your Oxygen sensor for proper output voltage. This would show up on a scanner but when the O2 fails it does not always set off a Check Engine Light if it is in the process of failing. If the O2 is not working properly the engine will not run or run very poorly after it transitions to "Closed Loop".
The EGR system on my car had failed and it only affected the idle quality and I never would have known about it until the car failed the Emissions test here in Virginia. The NOX goes way up when the EGR fails. On my 1988 C4 the EGR failed because the EGR Vacuum Solenoid failed. The EGR's Vacuum Solenoid is located near the thermostat housing on the drivers side. When I bought the car the hoses were in terrible shape and the EGR Vacuum Solenoid was not getting vacuum, I trimmed roughly 1" from the ends but the lines continue to break down until all were replaced. If the EGR system is frozen and non-functional it too will affect your idle when the engine is warmed up.
I hope that this helps a bit! The experience that is represented here on the Corvette Forum is really incredible. There are so many fellow Corvette Enthusiasts out here anxious to help resolve your issues with your Corvette!
01-02-2019, 09:34 PM
#28
Drifting
Thread Starter
EDIT: The last thing you did to the car before the onset of symptoms was "you put a BATTERY in it".
Are you sure the terminals are tight?
DID you inadvertently connect the battery in Reverse Polarity? You would have made a big spark. I mentioned the damage to the seat controls because of this, but the alternator can also be damaged by Reverse Polarity. How is the battery voltage when it runs crappy?.
"Sensors" do not develop faults while sitting. I feel the participants in this thread are over-thinking the "Clear Flood Mode" aspect. I don't think you're actually in Clear Flood, but have the throttle depressed far enough to lower MAP (remember it's a 91 guys, it has a MAP, not a MAF) enough that the mixture is richened to get it to restart. If there is NO BLACK SMOKE upon the hot re-start, it isn't running rich. I think it is running LEAN, and you get it to restart by lowering the MAP by opening the throttle. Lack of fuel delivery (pump) and faulty injectors will make it run LEAN, and fit my hypothesis.
Are you sure the terminals are tight?
DID you inadvertently connect the battery in Reverse Polarity? You would have made a big spark. I mentioned the damage to the seat controls because of this, but the alternator can also be damaged by Reverse Polarity. How is the battery voltage when it runs crappy?.
"Sensors" do not develop faults while sitting. I feel the participants in this thread are over-thinking the "Clear Flood Mode" aspect. I don't think you're actually in Clear Flood, but have the throttle depressed far enough to lower MAP (remember it's a 91 guys, it has a MAP, not a MAF) enough that the mixture is richened to get it to restart. If there is NO BLACK SMOKE upon the hot re-start, it isn't running rich. I think it is running LEAN, and you get it to restart by lowering the MAP by opening the throttle. Lack of fuel delivery (pump) and faulty injectors will make it run LEAN, and fit my hypothesis.