Car stalls only when cruising at constant speed UPDATED

[thrust]

I am currently trying to fix a weird stalling issue on a buddies 03 GT. Car has an L32 Gen V setup in it now. As stated, ever since we installed the L32 and new PCM, the car will stall when you maintain a constant speed for about 10 minutes. if you feather the throttle every few minutes it will NOT stall. He has a cartuned PCM by Kevin and I think kevin has tried to determine the prob as well with no luck. We are at a loss right now....Everything is pointing towards some PCM glitch or something. Here is what we have replaced so far....

-crank sensor
-cam sensor
-maf sensor
-map sensor
-checked entire wiring harness
-IAC
-had kevin send a new pcm with custom tune

Can anyone think of any other possibilities? I am at a loss with this. I thought forsure it was something like a maf sensor. Kevin, if you could do me a huge favour and send me a bin for a stock L32 with GT gearing I would really like to load it to his PCM to rule this out. Thanks in advance to everyone.

Kyle

[GP-SE]

If you think it's the PCM why not get another physical PCM and swap it in, another thing connect a fuel pressure gauge and see if fuel pressure is low, perhaps when you feather the throttle it makes the fuel pressure regulator allow more fuel

[thrust]

I will check on fuel pressure....didn't think of that,.,,,its not the physical PCM for sure...Kevin thought that at first and replaced it with another PCM with the same tune....I am leaning more towards something in the tune....hence I'd like to try a completely stock L32 bin with GT gearing.

[Ty]

all speeds in any gear?

can you narrow it down any?

certain TPS %?

[GP-SE]

what throttle body are you running? I wonder if a bad TPS would cause this, Ty got me thinking.
Maybe at a certain throttle position the sensor has s dead spot and reports 0v to the PCM.

[thrust]

It happens mainly in 4th crusing at about 80km/h, but it has happened in 3rd as well.

TB is an L32 TB and the TPS was not changed, but it was scanned and voltage and readings all looked good all the way up and down. (maybe still a possibility?)

Also, to add some info about the stalling. It is very random as far as how long it takes for it to start back up. Twice it had to be towed. Both times it fired up later that day after it had been towed. Nothing changed on the car. Both times I checked it had no IPW trying to fire back up? Is that normal?

Keep it coming guys....I want to get this snag so bad....its been over a yr. Still awaiting Kevins reply.

Kyle

[GP-SE]

your not getting IPW? I would check the wiring for the Ignition module, it shares the same harness with the Crank and Cam Sensor, you say you changed both sensors, if possible swap out that little harness that goes to the Ignition Module\crank\cam sensors. Cam sensor is used as a backup and doesn't matter too much, but if you loose Crank signal the car wont start, and you wont get IPW. There is a ground wire in that little harness, make sure it's connected to the block or ignition module\coil bracket. Did you guys inspect the harmonic balancer\crank pulley to make sure the teeth on the back aren't damaged. If I wasn't getting IPW the first thing I would suspect is the crank sensor, next would be wiring.

[thrust]

Well, we did suspect crank sensor...I think it was the first thing we changed....Checked every wire on the harness, etc. Kinda at the point of drawing at strings now. My friend just informed me when he had Kevin send him his first tuned PCM(for the L32 swap as he had an 03 L36) it came up with a code....he said it read (Driver 2 Line 6) He said Kevin had just cancelled it or something....anyone know what that is....he is just convinced its the tune lol after everything he has replaced. We did put a GTP PCM in it last yr and couldnt get it to stall...mind you it was set for GTP gearing as well, but I wouldnt think that would have affected anything, so maybe he is right. I'm not convinced on anything yet....this thing just puzzles me.

[Pharos]

Call me nuts but don't some of our cars have a security feature that shuts the engine off if the PCM is missing some authentication? (I.E. chipped key, etc.)

Basically when it kicks in it won't let the car restart (shuts off the fuel pump) and it can last from 10 minutes up to god knows what...

just something to look into, I'm not sure if it could cause the problem your having.

[2000gpGT]

sound like an ignition module to me. get it to act up. and then when your having trouble getting it going. give the ignition module a tap. if it starts as you do that you know where your propblem lies. if you have no codes and youve done cam/crank sensors already im pretty sure its ignition module.

[GP-SE]

that security thing kinda makes sense, but wouldn't the security light start flashing? To test the ignition module, when the car wont restart pull a plug wire off and see if you're getting spark. How did you test to see no IPW? use a node light on the injector connector? The weird part is with another PCM the car works fine, so really I think that rules it out, get another PCM and have the gear ratio changed to 3.29

[thrust]

Keep in mind this is the second PCM Kevin has sent.....the original one had "Bad" in permanent marker on the bottom and my friend was having issues obviously. So he sent another one with the same tune and this same problem occured....I am starting to think more and more its the tune. Kevin sending back to back PCM's which are bad? Unlikely. We had a spare PCM and we cannot get it to stall with a factory GTP tune. Once i figure out how to change the damn gearing to 3.29 I will try again with a completely stock L32 bin and GT gearing. Just need a bin somehow. Havn't heard from kevin yet.

[GP-SE]

Keep in mind this is the second PCM Kevin has sent.....the original one had "Bad" in permanent marker on the bottom and my friend was having issues obviously. So he sent another one with the same tune and this same problem occured....I am starting to think more and more its the tune. Kevin sending back to back PCM's which are bad? Unlikely. We had a spare PCM and we cannot get it to stall with a factory GTP tune. Once i figure out how to change the damn gearing to 3.29 I will try again with a completely stock L32 bin and GT gearing. Just need a bin somehow. Havn't heard from kevin yet.

do you have a tuner? if yes just flash the stock GTP file, with the edit for the gear ratio. Or contact Will Overkill.
willoverkill@gmail.com

[thrust]

Yah, I just bought one actually to try and fix this problem. Still trying to learn how to use it lol

[thrust]

So I called my buddy to clarify about the ignition modual.....The first time the car did this after installed Kevins L32 tuned PCM he replaced the ignition modual...car still didnt start...then replaced crank sensor and it started. Thought it was solved, but as mentioned this has occured dozens of times since. The next time it stalled we replaced the cam sensor...still didn't start. Started on its own later on. The next time we had to have it towed...and my friend drove down to see Kevin about a new PCM as it said BAD in big letters right on the PCM. Gets the new PCM with the same original tune from Kevin and it fires right up. We think we have the prob again....NOPE. As mentioned, everytime it stalled no IPWs.

I'm stuck on it being the tune. I just got off the phone and he also updated me on something I didn't know. I guess when Kevin first loaded this tune it came up with something like 11 codes set. From Maf codes to the one I listed above. I find it really odd how we didnt have a single code set with a stock L67 PCM dropped inthere and didnt stall once. Makes me think its in the tune even more. I really hope this is not the case for what he had to deal with.

Any last thoughts based on that? This weekend I will def try and load a stock bin to his PCM.