Okay once again I will try to revive this and see what info I can get from my fellow J-body-ers.

I've read and read through pages of posts mentioning this problem and concerns, but none give a definate solution or a positive feedback to something they did that fixed the problem.

This is the vehicle and what is on it/new:
2003 Cavalier, automatic, with 169xxx miles
GM M62 supercharger kit (installed at 165xxx miles) with GM flash
ZZP 3.1" pulley, intercooled with dual pass endplate and phenolic s/c spacer
K&N intake
LSJ header with Borla cat-back exhaust
New sensors: ECT, pre-cat O2
New battery
New thermostat
RKsport beryllium coils
NGK Iridium IX plugs (originally OEM at .45, now 1 step colder at .38)

This is the problem:
Idling, in any gear, if you flick, blip, step on the throttle real quick and let go the RPMs:
1.) drop to 300 (lights dim) {the AEM UEGO meter shows a serious lean out (unreadable)}
2.) jump up {richens up to 12.0-13.0}
3.) comes back down and dips to 400 or so {leans out into the high15s, low 16s}
4.) goes up a little past idle (600 or so)
5.) and finally stabilizes at 500 {stoichometric again}

I've cleaned out the throttle body
I've replaced the TP sensor with 3 different ones
Now I read that you have to reset the computert when installing the new TP sensor, could that be why I saw no difference?
Next thing would be IAC valve but they are pretty pricey.

I would love to hear from others who have or had similar problems and any other problems arrising after the GM kit/flash.

Any info is appreciated. I am also opening another thread on the stalling and now uselessness on Low 1 and Low 2 after the GM flash on the automatics.

What's your fuel pressure at? I kinda had this issue when I was running the supercharger and small injectors, are you running the green tops or the ones with the kit? They may be to small with your mods, check your fuel pressure and you might buy an adjustable fuel pressure Regulator to bring the pressure up and help with your lean issue, I can tell you 10psi of fuel
Pressure can Make a Big difference especially when boosted I know the afpr really helped out in drivability of mine when I was running a 2.9 pulley with the dual bypass setup seein 16ish psi

fuel pressure is right around 45psi at idle, 50psi when cruising and 60psi at WOT.

It has been doing this since the s/c was put on in stock form, so I don't think the mods are the cause. It just seems to be a sensor or programming problem because at all other times it is running beautifully.


*On a side note: I installed a OEM AC Delco TP sensor and even though the throttle blipping idle drop persist, response is much better between throttle on, throttle off. It still does lean out during the beginning of that transgression and then immediately goes stoich or rich, depending on where the throttle is. Next up is IAC valve.

was this a kit? or did you piece it together, you may have wires crossed when you extended the iac and tps sensor? if you pieced together a kit.

It was a kit and there was no cuttin in the IAC or TPS wires, the only cutting/moving around was in the MAP and IAT wires.

I think that is what he meant

I have the exact same problem with mine. I read somewhere that it was because of how crappy of a tune the reflash is, but I'm not sure.

My 2.4 S/C with the GM reflash does the exact same thing. I've actually had it stall after backing out of my driveway into traffic. But it always dips if you blip the throttle. I just live with it

Yeah I've also heard that it is the crappy flash.

It's also stalled on, lol.

Eventually I will try the last remaining option, the IAC valve. If nothing then this is just how it is with the tune. :'/

sounds like you stale or mislabled gas. My car is stock with just blower kit. one time i wasnt paying attention and put some 89 in. It was running with symptons u described

octane is not going to affect non boosted operation.

dont waste your time and money throwing parts at it. its the tune. find a good gm tuner and your problem should be resolved.

Kinda sounds like what mine was doin, i had a bad tps


z28guy(KGM BEOTCH)

I'm back on the ecotec s/c reflash temporarily and I haven't, and never had any issues with it. The GM reflash is not the greatest because it runs really rich on WOT (most have seen 10:1 AFR on stock pulley), and is not tunable with HPT. Have you checked for any vacuum leaks? Did you have the computer reflased by a dealership or did it come with when you bought the kit?


Save your money. It might be worth something someday.

aside from getting rid of it and hp tuning it i dont know that theres a solution for that



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

Rare5spd wrote:I'm back on the ecotec s/c reflash temporarily and I haven't, and never had any issues with it. The GM reflash is not the greatest because it runs really rich on WOT (most have seen 10:1 AFR on stock pulley), and is not tunable with HPT. Have you checked for any vacuum leaks? Did you have the computer reflased by a dealership or did it come with when you bought the kit?

No vacuum leaks or anything like that. I have to agree that it might just be the tune. Still haven't tried the IAC valve. Although I did flush the tranny system (automatic) and it seems to be responding better to throttle input, but it still dips. As others, I've learned to live with it.

Rare5spd wrote:I'm back on the ecotec s/c reflash temporarily and I haven't, and never had any issues with it. The GM reflash is not the greatest because it runs really rich on WOT (most have seen 10:1 AFR on stock pulley), and is not tunable with HPT. Have you checked for any vacuum leaks? Did you have the computer reflased by a dealership or did it come with when you bought the kit?

Not tunable with hptuners?


GMR has got nothing on this

Gm locked the Eco s/c reflash. Can't go in with HPT and edit the tune. Only thing you can do like suggested above is to get another PCM and get it tuned.


Save your money. It might be worth something someday.

Oh okay. Well how is it that we are able to get an unlocked LD9 s/c reflash?


GMR has got nothing on this

My guess it was unlocked form the beginning. It was readable, and hptuners was able to support it.



To the OP, I know you said you didn't find any vacuum leaks, but Id like to rule something out. Did you cap off the little port on the throttle body adapter?










Save your money. It might be worth something someday.

can't see it being an issue with the tune.

what does the car idle at when you start it will it stal theen or only when you rev it up



JBO since July 30, 2001

idle air control valve/motor....

check it...replace it...

NOTa2_4 wrote:can't see it being an issue with the tune.

what does the car idle at when you start it will it stal theen or only when you rev it up

It idles right at 500-ish. it stalls when going from drive to reverse (or vice versa) and it dips when you blip throttle, stalling sometimes.


EvoFire: Only thing left to change. Kind of like my cooling system. Only thing keft to change is the water pump.

trust me... its yoru iac... and yoru cooling system is fine....ur just paranoid.

i got my heat exchanger on yesterday and my car runs fine.

its the same as the ld9 they all hav a problem with the iac valve on the tb if you run the car somhow they stay stuck open or close they do both. im not sure if its the heat or not. i found after changing mine 3 times that there was oil on the wires connecting it.( cleaned mine and it fixed it) and the last one i installed was from a quad 4 2.3l no problems for the last 5k MAKE SURE U TAKE OFF YOUR BATTERY CABLE FOR ONE HOUR TO LET YOUR COMPUTOR RESET. IF YOU DONT YOU COMPUTOR CAN MAKE THE SAME THING HAPPEN