Surge at Idle
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Sorry guys - I found the problem... I didn't wait long enough to find out if my fuel pressure was holding @ 40psi. I waited 10 minutes and the pressure dropped 14 psi! 
I lifted the fuel rails and found not one injector leaking! That is the good news - however is the pressure regulator toast? That's my only other guess
I lifted the fuel rails and found not one injector leaking! That is the good news - however is the pressure regulator toast? That's my only other guess
Le Mans Master
Joined: Dec 2000
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From: San Diego, Ca
Difficult to say as the pressure will bleed off eventually - does it immediately restart or is there a long crank? If not, and if the pressure isn't fluctuating at idle, don't think this is the problem.
1st Gear
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I had the same prob on my 94 camaro LT1 and it turned out to be the opti. The motor was running a little rough (very little) and the cpu thought the motor was going to die and therefore opened the IAC to save it. I had a buddy scan it w/ a Snap On Motis (I think this is the name) and it mapped the sensors in real time and the IAC count would shoot up and cause the surge. Changed my opti and no more problems. I think I had the "low resolution pulse" code also, meaning a weak spark sent from the opti. Good Luck
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It takes about 3 - 5 seconds to crank after it is warm (noticeable cranking). Starts right up when engine is cold. Measured the pressure @ idle around 38 psi with regulator vacuum line attached. Measured regulator with vacuum line off @ 42 psi. All injectors measure between 12.7 - 13.1. The pressure drops noticeably after a few minutes and around 14 psi after 10 minutes.
Le Mans Master
Joined: Dec 2000
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From: San Diego, Ca
Doesn't sound like a pressure problem based on what you're seeing/posted, though you might improve hot restart with a new check valve which usually entails a new pump. You might recheck key on pressure after it's shutdown hot. Remember, a slight maninfold leak, say from an EGR pintle that isn't square in the bore is going to cause the same difficult crank (as well as the surge). Your injectors do appear to be weak - are these hot or cold #'s? There's a difference (technically if you will) between a surge and a miss. It sure would help to see a full scan with all the numbers. How many miles again?
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Doesn't sound like a pressure problem based on what you're seeing/posted, though you might improve hot restart with a new check valve which usually entails a new pump. You might recheck key on pressure after it's shutdown hot. Remember, a slight maninfold leak, say from an EGR pintle that isn't square in the bore is going to cause the same difficult crank (as well as the surge). Your injectors do appear to be weak - are these hot or cold #'s? There's a difference (technically if you will) between a surge and a miss. It sure would help to see a full scan with all the numbers. How many miles again?
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In park, If you hold the throttle to increase to a steady 1K rpm, do you notice any surge ?
Held throttle @ 1K rpm no notice of surge.
Held throttle @ 2K rpm no notice of surge either.
Double checked that all vacuum lines are not cracked or leaking.
Any way to test the opti?
Held throttle @ 1K rpm no notice of surge.
Held throttle @ 2K rpm no notice of surge either.
Double checked that all vacuum lines are not cracked or leaking.
Any way to test the opti?
Le Mans Master
Joined: Dec 2000
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From: San Diego, Ca
I'd find out if it's correcting for a Rich or Lean condition - If Lean, air is coming through from somewhere other than the MAF; Rich, possible misfire - Opti. You troubleshoot either by following the 44 or 45 chart.
Melting Slicks
Joined: Oct 2004
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From: Austin Texas
Test theory by unpluging IAC, does surge stop ?
as Bill Murray says :
"baby steps.....baby steps"
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Tested the EGR valve to make sure diaphram operating correctly and it is! Pulled vac hose on fpr and no smell of fuel! So, after testing everything I can think of - I am leaning towards a bad opti.
I started the car cold this morning and let it warm up to op. temp. and it only surged a few hundred rpm's twice in 15 minutes! Since, I am not getting consistent surging once warmed up - it must be related to the opti?
MAP sensor is holding steady at 1.35v - 1.37v
Melting Slicks
Joined: Oct 2004
Posts: 2,510
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From: Austin Texas
I apologize for the large pic, but I want to show you what my original Opti looked like after only 59K miles. I was shocked at all the moisture ingress, corrosion, and overall bad condition this unit was in when I replaced it. This of course illustrates the major drawback to the non-vented Opti's. Also, my WP was in just as bad shape, bearing cover seperation, a few ball bearings gone, siezed up weep hole, etc. The WP was original as well as the Opti.
And my car was very well maintained by previous owners, with all repair documentation dating back to its birth in '94.
So, your problems may very well be Opti related :
And my car was very well maintained by previous owners, with all repair documentation dating back to its birth in '94.
So, your problems may very well be Opti related :
Last edited by MikeC4; Dec 31, 2008 at 09:50 PM.
Le Mans Master
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From: San Diego, Ca
IAC does not correct for a Rich or Lean Condition - O2's report amount of oxygen in the exhaust and the PCM pulses the injectors more/less to keep the fuel mix right. As load and rpm increases, need for correction is diminished under either scenario. That's why it can smooth out when you open it up. A scan shows you what's going on and there are specific items to check depending on whether it's rich or lean. A misfire is different and the engine can stall - or allmost stall - and it's generally present when you add throttle - load makes it worse. This is why you scan it - capture Block Learn at idle and then in a couple of other cells. Monitor Targeted vs Actual idle - IAC counts - a/c request and CTS - and TPS voltage. It will narrow it down so that you can figure it out. You've posted some scan data - get the rest and we can help you better.
Melting Slicks
Joined: Oct 2004
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From: Austin Texas
Is this an Average that is calculated over time and various driving conditions(ie idle, acceleration, cruise, WOT) as it obviously can't be base timing...... I've never had an idle surge or erratic idle problem in any o fthe C4's I've owned, so I plead ignorance to EST.
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IAC does not correct for a Rich or Lean Condition - O2's report amount of oxygen in the exhaust and the PCM pulses the injectors more/less to keep the fuel mix right. As load and rpm increases, need for correction is diminished under either scenario. That's why it can smooth out when you open it up. A scan shows you what's going on and there are specific items to check depending on whether it's rich or lean. A misfire is different and the engine can stall - or allmost stall - and it's generally present when you add throttle - load makes it worse. This is why you scan it - capture Block Learn at idle and then in a couple of other cells. Monitor Targeted vs Actual idle - IAC counts - a/c request and CTS - and TPS voltage. It will narrow it down so that you can figure it out. You've posted some scan data - get the rest and we can help you better.
Scan Data:
Idle Air Motor 15 steps
MAP Sensor - 1.37v
Throttle Sensor - .60v
Left Block Learn 120
Right Block Learn 119
Blk Learn Cell 16
Left Integer Value 132
Right Integer Value 133
CCP Duty Cycle 0%
Idle Air 8
Spark Advance 23 degree
EGR Cycle 0%
Learned Cycle 15
Idle 625
Battery 14 v
Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Scan Data:
Idle Air Motor 15 steps
MAP Sensor - 1.37v
Throttle Sensor - .60v
Left Block Learn 120
Right Block Learn 119
Blk Learn Cell 16
Left Integer Value 132
Right Integer Value 133
CCP Duty Cycle 0%
Idle Air 8
Spark Advance 23 degree
EGR Cycle 0%
Learned Cycle 15
Idle 625
Battery 14 v
Idle Air Motor 15 steps
MAP Sensor - 1.37v
Throttle Sensor - .60v
Left Block Learn 120
Right Block Learn 119
Blk Learn Cell 16
Left Integer Value 132
Right Integer Value 133
CCP Duty Cycle 0%
Idle Air 8
Spark Advance 23 degree
EGR Cycle 0%
Learned Cycle 15
Idle 625
Battery 14 v
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All Scan Data w/ Idle Surging:
Prom ID 4681
A/C Pressure 67 psi
MAP Sensor 1.19 v
Throttle Sensor 0.60 v
Bat Voltage 14v
Manifold Air Temp 81.2 degrees
Left O2 61mV
Right O2 48 mV
Left Block Learn Value 122
Right Block Learn Value 120
Blk Learn Cell 16
Left Integrator Value 125
Right Integrator Value 123
CCP Duty Cycle 0.0%
Idle Air Motor Position 26 steps
Spark Advance 17 degrees
Desired Idle 675
Engine RPM 800
Knock Retard 0 degree
Throttle Angle 0%
EGR Duty Cycle 0%
Learned Idle Position 16 steps
TCC Status - Not Locked
CCP Purge Off
Learn Control Enabled
Loop Status Closed
Prom ID 4681
A/C Pressure 67 psi
MAP Sensor 1.19 v
Throttle Sensor 0.60 v
Bat Voltage 14v
Manifold Air Temp 81.2 degrees
Left O2 61mV
Right O2 48 mV
Left Block Learn Value 122
Right Block Learn Value 120
Blk Learn Cell 16
Left Integrator Value 125
Right Integrator Value 123
CCP Duty Cycle 0.0%
Idle Air Motor Position 26 steps
Spark Advance 17 degrees
Desired Idle 675
Engine RPM 800
Knock Retard 0 degree
Throttle Angle 0%
EGR Duty Cycle 0%
Learned Idle Position 16 steps
TCC Status - Not Locked
CCP Purge Off
Learn Control Enabled
Loop Status Closed
