need some help, car surging

[99camaropkg]

lately my car has had a surge between 1k and 2k rpms. when ever i let off the gas and start to coast as soon as the rpms get between 1k and 2k it feels as if the car is surging like i have bad brakes but the brakes arent applied. If there is anyone who can help me with this please i need it. would new gears or new torque converter fix it. or resetting the pcm maybe. i dunno. it has 100k miles on it and it is my daily driver. need help fast.

[Justin Kirkham]

Does it do this at idle?

-Justin

[99camaropkg]

it doesnt surge as much as it is rough at idle. when it surges it kinda feels like it dont know what gear to go in . so...rough idle..but surge when coasting.

[strange_trp]

vacuum leak or EGR stuck open, 1st things to check.
possibly MAF but you'd see problems throughout the RPM range. also MAYBE the TPS but not as likely.

rough idle and surging complaints are usually due to a vacuum leak.

[99camaropkg]

i just had $600 worth of gaskets installed to fix a vacuum leak about 3 months ago, could it be that those failed? if so should the dealership that put them on be responsible for it?

[strange_trp]

dunno. i'd check vac hoses first.
may be an egr problem but you'd probably have ck engine light in a 99 model if egr sticks.
vac leaks may not cause ses to come on.
possible hose, maybe an intake manifold gasket but this is less likely.
use propane to trace all vacuum lines and around the base of the intake manifold with the car idling. they make propane gas wands for this purpose. of course you don't light the torch, just use the gas. a vac leak will suk the propane into the intake, smoothing your idle and slightly raising rpm. rule of thumb is 1 inch per second as you move.
another possibility is that vac hoses to the evap canister purge solenoid are installed incorrectly.
did this problem start suddenly? have you done anything in the engine compartment or climate control system just before the problem started? do you still have power brakes? hear a hissing noise behind the dash panels? done any work where you had to remove and reinstall vac lines?

jsut some possibilities.
rarely do intake manifold gaskets leak, though. i'd take it back if it hasn't been all that long and you have done nothing else to it.
the symptoms point to vac leak.
another question: how does it run at WOT? vac leaks usually surge and sputter at idle, decel, and low speeds but the engine will run fine at wide-open throttle.

[99camaropkg]

it runs great at WOT. i didnt notice it until i was leaving the track the other night. but i made my personal best run b4 i left. i had the intake manifold gasket changed already and that was a crap load of money. if there isnt an ses light on would there still be an error if checked?

[strange_trp]

i'd say definately a vac leak.
vacuum leaks will not always set lights, even with OBD-II.
check for leak yourself with propane or have a technician do it. also remember your power brake booster and your climate controls inside use intake manifold vacuum to operate, as well as the evap cansiter purge system (although if you get the solenoid hoses on backwards you probably will see an OBD-II code)

[99camaropkg]

just left the technician and he said that it is more than likely not a vac leak because there is no whistle noise that accompanies a vac leak. i am going back later when he gets his diagnosis machine and get it hooked up to see. Could it be gears not knowing what gear to change into. it is making a popping noise in the rearend when it is surging now. anymore ideas

[99camaropkg]

update: just got it scanned, it is the egr valve sticking every 5 minutes.

[strange_trp]

a vac leak will not always cause a whistling noise.
egr sticking open is just like a vacuum leak in that it is letting unmetered air into intake manifold unexpectedly.
glad you found the prob

[redcamaro1996]

Re: need some help, car surging

Hey, I've got a '96 3.8 and my hunch is that it is also the EGR. When the PCM is scanned it doesn't show that the EGR has thrown a code. Is it possible that the intermittent jolt/sputtering is the egr and the computer just isn't getting the code? How did you determine that the egr was throwing the code every 5 minutes?


*Note - let the Cat. converter go many months before replacing it, could that increased backpressure caused exhuast temps to screw with the EGR?

Thanks.
Mike
1996 Camaro 3.8
Flowmaster kit
magnaflow highflow cat
Centerforce dual friction clutch
KN intake