This is an odd one, and I would appreciate your help.

Car:
1996 Chevrolet Camaro: 3.8l V-6, 5-speed transmission.

Problem:
At first intermittent, now permanent: Vehicle cranks, starts and dies IMMEDIATELY, if you press the accelerator pedal, the vehicle will run, until the accelerator is released. Car runs a little rough, but not misfiring. With a Cold Start the vehicle will run, ignition is cycled off/on and the problem reoccurs (not sure if it's temp related as with heat soak it has restarted before.)

Read Fault memory with a Snap-On Red Brick, no codes in history or currently present.
Fuel Pressure >40psi
Spark Present
Fuel pressure regulator replaced recently, checked again, no fuel in vac line.

After looking at all values, swapped in a known good: MAF, MAP, TPS, IAC, I left in the new IAC as the counts were @70 with the old actuator, and with the car idling the counts WERE at 10-20 immediately after the IAC was replaced. On a random start the IAC was at 56 Counts and was idling

The Scanner Says the ICM (ignition Control Module) is in "Bypass" Mode indcating an error,(green corrosion on pins to coils) replaced ICM and routed the Spark plug wires away from harness, still won't idle (wires to be replaced tonight, but spark present in all 6)

Test MAF smoothed running, but did not idle. (OLD MAF is still installed)

The car smells a little rich but all 4 O2's say the mixture is at stioch and they switch, but they're at 112,000mi so they're old.

Full tank of Medium grade gasoline, reputable brand, no noticable loss of power at WOT on the freeway.

I'm stumpped at this point, excluding a Bad PCM I can't think why the vehicle won't idle. and furthermore WHY the ICM is in bypass mode and no codes are thrown.

I want to accurately diagnose this instead of throwing parts at it, partially because I want to learn the car instead of guess and check, and secondly because I have a new motor to swap in and I'm $10k off and I don't feel like restoring my L36, I just want it to run well. ANY good ideas are appreciated. Thank you.

 

have u changed or checked the spark plugs? if u looked at em what did they look like?

 

I was so going to say that. Would you have a spare EGR valve lying around? If it is not sealing it could cause the issues with idle.

 

I'm in my driveway so no plugs yet, but I know the wires are bad (didn't think that would cause a stall, but I have new ones)

I can check the EGR, but it was replaced in '04 for a fault in the position sensor, and the line was rechecked in '06 when I resealed the intake and did head gaskets. at which time ('06) I replaced all 6 spark plugs with the factory irridium ones

 

I think Craby wants to know what the plugs look like more then thinking they are bad. What the plug looks like is a indicator to what is going on in the motor.

If your O2 sensor have not been giving good data and your car has been running a little rich it can soot up the EGR valve port in just a few thousand miles.

 

Good call, the fuel presure regulator was bad for a long time before I replaced it so that makes sense. I'll check the EGR when I get home.

 

My wife's Alero was doing this same thing only once her car warmed up it would stay running. This problem was 2 items at the same time. The first was the Fuel Pressure regulator on the fuel rail and the second was a failing (but not yet failed) fuel pump. Fuel pressure was too low at initial start up (fuel pump caused this), but it was at proper idle pressure once this engine was warm. I did the regulator first and that only made it so the car would idle sooner without my assistance. I would have to "prime" the engine to get it to start before doing these and once it would start I would have to 2 foot drive it to keep it from dieing. Priming is cycling the ignition on and off a few times to build up the proper pressure to start the engine. The fuel pump was my next point of failure. Once it was replaced the car would start and idle without staying on the throttle.

The ignition module being in "Bypass" mode could be because the engine is still running in open loop. It should switch into normal operation once the engine reaches operating temp. The Module can be put in bypass mode if the signal from the Crank Position Sensor signal is eratic or weak. A failed CPS will throw a CEL but a failing one does not always throw a code. A failing CPS can also cause the dredded P0300 random misfire code. Also This will allow the coils to fire at a "best guess" to what the engine requires. It works sometimes but needs a good pulse from the CPS every now and then to maintain the guessing.

The Cam Position sensor will not cause these issues since it only assists in the firing of the V8 coils and not the V6 coils. The V6 has a waste spark system that fires 2 cylinders at the same time. This only requires the computer to know where the crank is and not the cam. On the other hand the Cam PS is what lets the computer know what injector to fire and when.

I hope this helps you get your car running right.

Massey

 

So the EGR is free and clear but there is still a very rich mixture. A friend seems to think PCM, I checked, and the typical water dammage is not present so the simple info on the fault is this:

Ignition mode is ON so the the ignition is controlled in a default failsafe manner.
The IAC couns are above threshold, even after replacement. 5-50 spec, mine's at 70
Car starts and idles cold int. restarting will cause reoccurance of the failure.
cannot control IAC with scanner to modify idle, but a/c will modify idle.
IAC and ICM replaced. any thoughts?

 

have u taken the 02 sensors out and looked to see what condition there in?

 

Yes check the crank position sensor. They can partially fail and cause what you are talking about. The full failure will result in no spark. If it is like the FWD 3.8L engines it will be in the front left near the harmonic ballancer. I have not looked my car over too hard to find mine so I am only guessing the location based on an engine I know quite well.

Massey