2G Odd idle issue

[LxiMax]

Hey all. Just picked up a 95 GST w/ 83k on it. Very clean and runs well IMO except in one area. At idle, it seems like it has a small miss that almost makes it feel like the car is going to stall. It won't drop below 600 rpms but will sit between 700 and 900. Under throttle is rides great, hits boost fine. Even when floored, it picks up and goes like it's nobody's business. Now I have a guess what it may be, but I could be wrong. It seems to have quite a decent exhaust leak before the cat. I'm leaning more towards that but I've seen too that it could be a dirty maf, the timing could be off a tooth, etc... Any and all help is appreciated.

 

[LxiMax]

I've also considered the EGR valve. That's my next course of action.

 

[cord]

My 92 eclipse gs had the same problems ,and come to find out it was the alternator was not putting out enough voltage and was surging electricity making it idle up and down


thanks for that! i have the same random stumble @ idle not a compleat missed fire. it just fells like a late fire. it started now that i think about it when the alternator got weak. i have a volt guage and noticed my alt struggles to keep proper voltage under any load. ill swap the alternator see if thats it.

 

[LxiMax]

Still having issues. Running out of ideas at the moment. Did a full idle adjustment ( SAS, TPS, and BISS ), 02's are good, CTS is good, ISC replaced, no boost leaks, charging system is good, no vac leaks. Planning on doing a leak-down test. Only thing that has seemed a bit odd was my TPS reading. On the low end, it was .72 instead of .63. Is this too far out of spec to cause an issue? The manual says .4 to .6 and many say settle to .63.

 

[miguelmcv]

Still having issues. Running out of ideas at the moment. Did a full idle adjustment ( SAS, TPS, and BISS ), 02's are good, CTS is good, ISC replaced, no boost leaks, charging system is good, no vac leaks. Planning on doing a leak-down test. Only thing that has seemed a bit odd was my TPS reading. On the low end, it was .72 instead of .63. Is this too far out of spec to cause an issue? The manual says .4 to .6 and many say settle to .63.

TPS will not affect your idle to much, but it will affect in respond.
If you did all what you just said and still have idle problems, then is time to check your ECU for leaking cups.

 

[LxiMax]

I strongly believe the TPS is my issue at the moment. I hooked up a Modis ( Snap-On Scangauge style machine ) and at idle it shows my TPS at almost 25%. Isn't that just a little high?

 

[LxiMax]

So after months of fighting, I decided to look in deeper places. Tonight I found my lower stock ic pipe corroded to hell. I can only imagine how the top one must look. Took it for a short drive after cleaning that up and installing my Dejon lower ic pipe and the idle has smoothed out a little. Now I have another question, when I'm in park and I rev up to 2k rpms, I'll have a little pop every so often. Is this a sign of further boost leaks or possibly coils or an igniter going bad?