2G idle issue

[Charlie90GST]

I'm just getting back into the dsm scene, I had a 90'GSt before, noe I have a 98GST, last sunday it started to run rough, the rpms bounced all over the place, then it backfired a few times and died. I had to have it towed home, so far ive replaced the plugs, plug wires, coilpack (it was bad) and the fuel filter. it runs now but the idle is a bit unsteady and i am getting occaisional hesitation on acceleration. its stock so far, I've just been getting the maintanence stuff done before I do any major mods.Any Ideas? I'm wonfering if it could be the IAC valve.

 

[Charlie90GST]

I checke for vacuum leaks, it threw the random misfire code before i replaced the aforementioned parts, no cel now though.

 

[Charlie90GST]

the isc is the only thing i haven't checked, yes the plugs are properly gapped. and btw its not going up rpms at idle, its going down.

 

[my dreamt dsm]

Did you just take off the battery? It'll take a while for the car to idle right again. 40 miles approximately.

 

[neuro_funk]

have you tested the TPS and the MAF to make sure their working?

i had that problem years ago and it was the MAF

 

[Charlie90GST]

i had the battery out for a couple of days, i'll test the maf monday, i'll be working for the rest of the weekend, thanks guys.

 

[Charlie90GST]

ok, tps and maf are fine. it was running rich, so as suggested I drove it for a about 3 miles and it threw a cel, cylnder 3 misfire. before it was random misfire, so i'm assuming the injectors are going bad, I had my borther in-law come over and check the injector pulse with a noid meter and they are all getting a good signal.

 

[Charlie90GST]

Ok, replaced injectors, everything seemed fine till I drove it to work. It's stuttering a lot less, but I am getting either misfire or detonation. What else could this be?

 

[fonzi90Tsi]

Mine started doing this and come to figure out that it jumped timing. Check to make sure all the marks are dead on.

 

[Charlie90GST]

But the last code it threw was for cylinder 3 misfire

ok, its not the timing, funny thing is that the stutter isnt constant, it does it once or twice every couple of minutes, but gets worse after its been driver 10+ miles. after about 14 miles the ilde started to bounce around about 300rpms or so, like the enginge wanted to die but the isc adjusted to kep it going. by the time i got 3 blocks from my apt it was stuttering every 20-30 seconds. it seems like the problem just gets eorse when the car warms up. to recap, i've shanged the spark plugs, gap is correct, plug wires, coil packs, and injectors. the only thing i can think of is either the fuel pump, pump relays, fpr, or the computer itself. any suggestions?

 

[Mitsubishigst1999]

What size injectors are you running are they to big for your tune or are they stock, and still running too rich mabye.

 

[jdoherty420]

Im having the same issue with my 97 gst.. has a rough idle and bounces between 800-1200 rpm. Idle drops down once iit warms up, but still has a slight surge to it. Mine also is throwing the same code for a cylinder 3 misfire. At first I thought it was just a relearn issue. The car was off the road for a while and has a freshly built motor in it. This issue is driving me nuts, ii already checked every thing prevously mentioned. Everything is stock motor, turbo, and fuel system wise. Im wonderng if you have solved your issue. I just can't figure this out. It runs strong, no issuess with acceleration, plenty of power. Coming to a stop the motor almost wants to stall, and idles really rough. The balance shafts have been removed. Other than that every thing is factory

 

[Charlie90GST]

I changed out the power transistor and it smoothed out somewhat but still drops rmp and acts like it wants to die and looks like raw gas from the muffler.

 

[92AWDHX40]

It may not surge but this may help too good reading regarding idle.