This one's got me stumped. 
C5 Timing Drop Out
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From: Reading, PA
C5 Timing Drop Out Hey guys, I'm in the process of tuning a T1 Z06. A little history. This car blew an engine during a race and the engine caught fire. All the wiring harnesses were replaced along with the engine and some other peripherals that were damaged in the fire.
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
If the reluctor was loose, can you see a fluctuation in the rpm or the (might have the number wrong cant remember what these motors are using off the top of my head) 24x signal?
I know on the Diesels when GM had that little problem of loose reluctors, we could acutally take the sensor out and try moving it to see if it was. Never ran across it in any of the gas motors though.
Also the coolant temp or iat temp isnt flaking out at times is it, telling it to pull timing?
I know on the Diesels when GM had that little problem of loose reluctors, we could acutally take the sensor out and try moving it to see if it was. Never ran across it in any of the gas motors though.
Also the coolant temp or iat temp isnt flaking out at times is it, telling it to pull timing?
Originally Posted by mikey
Hey guys, I'm in the process of tuning a T1 Z06. A little history. This car blew an engine during a race and the engine caught fire. All the wiring harnesses were replaced along with the engine and some other peripherals that were damaged in the fire.
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
Found it..
Not sure if this is your prob or not.... Hope it helps..
2001 Chevrolet Corvette
--------------------------------------------------------------------------------
Lack of Power Following a Wide Open Throttle 4-2 or 3-2 Downshift and Subsequent 2-3 Upshift (Reprogram PCM) #02-06-04-001 - (Jan 8, 2002)
Lack of Power Following a Wide Open Throttle 4-2 or 3-2 Downshift and Subsequent 2-3 Upshift (Reprogram PCM)
2001 Chevrolet Corvette With 5.7L Engine (VIN G - RPO LS1)
Condition
Some customers may comment that the engine lacks power following a wide open throttle downshift, either 3-2 or 4-2, followed by a wide open throttle 2-3 upshift.
Correction
A new service calibration is available for this condition. This calibration is available from Techline starting September 2001, on the TIS 2000 version TIS 10/2001 data update or later. Reprogram the PCM with the new calibration.
Not sure if this is your prob or not.... Hope it helps..
2001 Chevrolet Corvette
--------------------------------------------------------------------------------
Lack of Power Following a Wide Open Throttle 4-2 or 3-2 Downshift and Subsequent 2-3 Upshift (Reprogram PCM) #02-06-04-001 - (Jan 8, 2002)
Lack of Power Following a Wide Open Throttle 4-2 or 3-2 Downshift and Subsequent 2-3 Upshift (Reprogram PCM)
2001 Chevrolet Corvette With 5.7L Engine (VIN G - RPO LS1)
Condition
Some customers may comment that the engine lacks power following a wide open throttle downshift, either 3-2 or 4-2, followed by a wide open throttle 2-3 upshift.
Correction
A new service calibration is available for this condition. This calibration is available from Techline starting September 2001, on the TIS 2000 version TIS 10/2001 data update or later. Reprogram the PCM with the new calibration.
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Thread Starter
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From: Reading, PA
Originally Posted by Cobra R
If the reluctor was loose, can you see a fluctuation in the rpm or the (might have the number wrong cant remember what these motors are using off the top of my head) 24x signal?
I know on the Diesels when GM had that little problem of loose reluctors, we could acutally take the sensor out and try moving it to see if it was. Never ran across it in any of the gas motors though.
Also the coolant temp or iat temp isnt flaking out at times is it, telling it to pull timing?
I know on the Diesels when GM had that little problem of loose reluctors, we could acutally take the sensor out and try moving it to see if it was. Never ran across it in any of the gas motors though.
Also the coolant temp or iat temp isnt flaking out at times is it, telling it to pull timing?
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I am certainly no expert but this is what popped into my mind.
Have you disabled any DTC's? If so have you enabled them so it will post?
Have you checked/unhooked the MAF?
COT enabled?
Could it be a torque management issue?
Was the ABS module changed?
Was the TPS controller module changed? (The little module in front of the PCM, I tink it's called the ECM?)
I know these suggestions might be redundant, but I thought I'd give them a try.
Have you disabled any DTC's? If so have you enabled them so it will post?
Have you checked/unhooked the MAF?
COT enabled?
Could it be a torque management issue?
Was the ABS module changed?
Was the TPS controller module changed? (The little module in front of the PCM, I tink it's called the ECM?)
I know these suggestions might be redundant, but I thought I'd give them a try.
C5 Timing Drop-out
Originally Posted by mikey
Hey guys, I'm in the process of tuning a T1 Z06. A little history. This car blew an engine during a race and the engine caught fire. All the wiring harnesses were replaced along with the engine and some other peripherals that were damaged in the fire.
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
The engine runs perfect part throttle. At the onset of WOT, timing will drop from 38* part throttle to less than 5*. It does not happen all the time. Sometimes the dyno run will go to 5500rpm before we see it happen. Sometimes it is an instantaneous drop but will recover and finish out the run.
For some reason, the PCM is pulling all the timing out spuratically. No codes get set. It almost looks like the reduced engine power mode but then again, no codes get set. We replaced the obvious crank position sensor. Suspect might be the engine itself (crank reluctor).
Any ideas?
When I was having problems with the Gen7 DFI ignition cutting out, & suspected the relucter wheel, I used my lab scope & plotted the pattern, Checking for variations in frequency & occiallations on the graph, easy check and a sure-fire way to determine if there is a problem internally. Give it a shot!
Buster