I have a troubling issue with the car cutting off during hard acceleration. There are two scenarios for this issue

1.) From a stop if i take off full throttle the car will launch an accelerate as normal, but as soon as it reaches the higher RPM's (5-6k) it cuts off. The engine is still on, but is just idling at 3-4k and the car isn't moving, like it's in neutral. The A/F gauge reads super rich (bottomed out at 10.0:1).

2.) From a roll I get on it and as it shifts down, it catches and launches forward for like 1/2 second, and cuts off as it 5-6k RPM. Same thing, the engine is still on, but is just idling at 3-4k and the car isn't moving, like it's in neutral. The A/F gauge also reads super rich (bottomed out at 10.0:1).

Afterwards if I release the gas pedal it returns to normal, but if I get on it again too soon or too hard it does the same thing and cuts off.

I am a little bit stumped here. So far the coil pack, boots, and springs were replaced and it went away, but now it has come back with a vengence. I just replaced my old (15K mile old) NGK 6509s with $20!!! NGK 3787s. When I get off of work I'll see if that changes anything.

But in the meanwhile I just wanted to see if anyone else ever had a similar issue.

What injectors and fuel psi? On GM Crap Flash?





P&P Tuning
420.5whp / 359.8wtq

Ryan AFAIK all that is still stock on his car. so yea the "Crap Flash" and yes the 36 lb/hr injectors and probably stock fuel PSI.

Check for dead spots on in your MAP sensor readings. You will need a scanner that can read individual PID readings. Sounds like a MAP issue but again this could also be several other things.



ASE Master Certified Automotive Technician

As EvoFire stated, yes crap flash, 36 injectors, and fuel pressure is between 63-68 PSI at those RPMs before it cuts off and after it cuts off it sits at 45-50 PSI like it's at idle.

MAP sensor did cross my mind, but it's an expensive M*F*! The symptoms do seem to be of the PCM recieving info that indicates the possibility of the powertrain becoming damaged and it is commanding the engine to cut off and the transmisison to switch to neutral in order to prevent such damage. But since last time the replacement of the coil boot and springs fixed it, I decided it might be ignition related. I just dropped $80 on those plugs, so hopefully they'll at least make a difference.

As a note, this began 2 weeks after I swapped the transmission with a rebuilt one w/ TG LSD and Raybestos Stage clutches, swapped to LSJ cams (INT and EXH), and replaced the timing and balance chains. For those 2 weeks the car was a dream to drive, then this happened, then it got fixed, and now we are back to this.

I've also considered a bad engine harness (since the blue plug that goes on the PCM has some brown discoloration at the connecter {like when the wires draw too much amp and get ho}t) or the PNP switch (since I randomly get a code for the Transmission Fluid Position Switch being in wrong gear {and it's not the TFP switch because I got this code with both the old and rebuilt tranny} and the whole LOW and 1 LOW 2 gears don't operate properly {which I have another post about it somewhere}).

Is 10:0 the richest your wideband reads? I'm thinking it is flooded out.

Regardless I think it is tune related. Be it the crapflash, or actually tune. Whichever you have.



FU Tuning

Yeah that's the richest the AEM UEGO reads. It only goes 10.0:1 after it cuts off, before it cuts off it's doing normal (10.3-11.9:1 at WOT).

there is too much "work" done to this car to run the GM Reflash IMO. The difference in cams alone requires a retune. the trans being "built" will require tune for for the trans too. I think you are in over your head with out a HPT tune. i think this is all tune related. And i dont think it is because the Gm Reflash is bad. I think its because you have gone above it capabilities.

To an extent I'll give you that.

The cams might be an issue, but as far as I've read, they don't cause too much of a change other than the exhaust valve is being left open a little longer.

As for the tranny having the Raybestos clutches, shouldn't matter.
But the LSD, maybe since the tranny requires to turn both axles equally now, instead of one and letting the other one catch up. But still, don't think the tranny is the problem.

Although a good custom tune would definately be much better, it still seems like this might be a sensor or a wiring harness problem.

its probably more of a change then you think...its cool.

you are one of those guys that will ask for help and opinions and then tell people they are wrong. we have already established that.

you dont see the ld9 guys going from stock cams to HO cams and not tuning do ya? you dont see the SS/SC and SS/TC guys swapping cams and not tuning do ya? you dont see people go from stock cams to Comp Stage 1's and not tuning do ya? get my point?

It is not likely the cams that are causing this issue. Is your mod list up to date?



ASE Master Certified Automotive Technician

Toss that POS crapflash tune in the garbage and get someone to actually tune it with HP Tuners. Im willing to bet your symptoms are the same as mine were, but you have a wideband and auto witch i didnt. My problem was the crapflash itself. Swapping out ECUs and getting tune with HPT was the best thing i did for the car.


Error: Sig not found.

EvoFire I am not saying you are wrong, just saying my opinion. If my opinion is wrong, then please correct me.

CaliforniaDomestics: Yes my mod list is up to date.

I am not going to lie Tinkles, a HPT would be awesome. I even got the extra PCM, just need the HP Tuner and someone to tune it.

change plugs and report back.



13.3 @ 106 mph Cammed

I agree with the map my self.

Plugs have been changed and.... nada. Same problem.

I attach the shop scanner to check for codes and got these:
P0300 Random Misfire - Had this come up before. I previously changed the ICM with the coil pack before the boots and plugs, but it made no difference and returned it. Now that is the only thing in the ignition department that hasn't been changed, so maybe?
C1225 Left Front Wheel Speed Sensor Is Erratic - First time it's come on. IDK. CODE Fix says replace WSS or repair WSS harness.
C1275 PCM Requested ETS To Be Disabled - Also has been present before. I've seen this triggered before when the PCM fails to recieve a signal from a vital sensor. TRAC OFF light comes on, cooling fans are forced turned on, and the transmission goes into limp mode. Suprisingly the CODE Fix says the the ICM is one possibility...
C1295 Brake Lamp Switch Circuit Open - Also first time. IDK. CODE Fix had nothing for it.

That's all there is at the moment. I'll look into the MAP sensor again, but last time I was logging data it seemed to do fine. It rose exponetially during acceleration and dropped to a flat line when the engine cut off. Also going to look at the ICM again, but don't have high hopes for it. Could possibly be a harness problem like a stripped or stretched wire, too. I've been looking for a spare harness at the junkyards, but they are either cut, mawled, manuel trans, or missing ABS.

Another thing where is the EBCM located?

check the voltage from your map with a volt meter and see what it is saying through the scanner. if they are different replace ecm. had this issue on an factory n/a setup. guy showed me this and replaced ecm and was amazed that it fixed the problem. just a start.

Yep , I had the same with a boosted ECO.

In this situation you cannot call the GM supercharger flash..."the GM crapflash" It is a tune for a certain setup. You cant just download that tune on a custom setup and expect it to run right. Im not saying this is your number one issue but just want to point that out. Albeit there is a difference in the GM flash and the HPtuners GM flash. But thats a whole another subject.

Just as my own experience I had a similiar issue. I thought it was the stock coil pack housing so I swapped in some spark plug wires. Well turns out it wasnt that just one fuel injector connection was loose. But with your issue only at that specific range of RPM's does sound like a tuning issue.



GMR has got nothing on this

even on a stock Supercharger setup the flash is crap.



FU Tuning

Update: Keep on getting a P0300B randomly. You can feel small misfires at idle and low RPMs, plus if you watch the dome light a night you can see it dim down when it misses. I mean when I WOT the tranny kicks and it takes off, even break loose the tires ever so often, so the power is there, just something is tripping the PCM.

I have considered the PCM being bad. I may end up bitting the bullet and see if the dealer will reflash another PCM to my VIN and S/C setup. But first I want to make sure it's not the harness or a sensor sending bad info.

As for my 2 cents on the GM tune itself, it's good for a dealer/"factory" tune, but that's all. Like any car, if you mod it or want more out of it, you need to custom tune.

I didn't think we could use lsj cams in our cars??

Your issues are tune related.



FU Tuning

I'm not convinced this is related to the tune. Your lights dimming during the misfire is interesting though and I think warrants further investigation. Check for corrosion on the harness pack under the battery box and the ignition signal (power, etc.) wires from the fuse box (under the hood fuse box). These cars are notorious for corrosion issues in these two areas that cause strange issues that are similar to your description as well. Sometimes these issues throw codes, other times they do not. You have mentioned a couple other things that previously led me to think there may be an electrical issue going on so this might be more confirmation of that. I really wish I could see the freeze frame data during the issue to assist in narrowing this down. In regard to the GM reflash being no good I suppose it depends upon how you view this but for what it was intended for and even well beyond, it's plenty good in my opinion/experience with it. Could it have been better? Of course but again remember what it was initially intended for. In general our ECU's table resolutions and features are crap to begin with so even with a great tune with HPT it still sucks in comparison to what you can do with just about anything else on the street.



ASE Master Certified Automotive Technician

Very well said on the tune CaliforniaDomestics.

I know the corrosion you are talking about thanks to the previous owner using a cheap battery. The fuse box area has been inspected and is in great shape. The wiring under the battery tray has shown signs of acid having fall on it, but no corroded wires on the outside, inside who knows.

The funny thing is the time that it fixed itself I had done two things, replaced the boots/springs on the ignition coil pack and had actually pulled the engine harness to check it out. When I put it back on it ran fine, until last Wednesday.

Time to search for an auto a/c abs harness.