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.

 

[troppo loungo]

Exhast leak should not effect the idle. Could be your Biss screw or TB shaft seals are leaking. Check for vacum leaks around the TB by using a tube to your ear and the other end around the TB and listen for a hiss. Could also be you ISC or an EGR issue. How does it idle when the engine is still cold?

 

[LxiMax]

Idle is smooth on a cold start. Will rev to about 1500 rpms and slowly come down, then start to sputter around 900 rpms.

 

[troppo loungo]

Ok, well the FIAV seems to be working but could still have issues. check the other stuff I mentioned.

 

[LxiMax]

Will check this out in the A.M. Have to go pick up a Haynes and Chiltons. I have a lot to learn about DSM's, I won't lie .

Checked all the hoses and gaskets, no issues there. Still have to check the sensors.

 

[LxiMax]

No vaccum leaks, cleaned the throttle body and readjusted the Biss screw and it idles between 700-900 rpm in Park. One coil pack was bad and I replaced it but still the slight sputter at idle persists...

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

 

[LxiMax]

It doesn't have a fast idle like jumping up to 1500rpm. It literally jumps maybe a 100rpm and just flutters. I'm thinking maybe even the EGR valve could be causing it.

 

[92AWDHX40]

Again a lot of us say its not surge but there is a lot of information on idle there, there are several things there to help with idle, surging or not there is a idle issue there, and a lot can be learned by reading the above thread and ruling out things as you go.

 

[LxiMax]

Ok I gotcha. I'll go through it some more and see if I can narrow it down.

 

[93dsmwi]

i had this same problem took to the dealer and they said it had the wrong plugs in it and a boost leak of

 

[Abe'sGST]

what i would do if i was you, i would first of check for any misfire, plugs, wires, and fpr. im guessing your running stock?

 

[icancruz]

I think you need to first make a clear distinction about whether it's a misfire or a surge. There is a definite difference, and ruling out one or the other will greatly help in your search to find the problem, because it'll point you in one direction or the other

 

[miguelmcv]

If everything is working good as you stated and you just feeling that intermediate Idle, then It should be your plug wires or the plugs it self, But I would start fixing the exhaust leak first, which it can do some sore of craziness in the ECU, which the rear O2 sensor is not catching all the fuel burned.

Fix the exhaust first, If problem persist, then go and replace your plugs and wires.

 

[icancruz]

That's another thing, it could be your O2 sensor(s). A bad one can cause loping idle

 

[LxiMax]

I bought the car bone stock w/ the jumpy idle. First thing I did was change the plugs and wires. Odd thing was that the plugs and wires were newer, however, the plugs were Bosch +2 Platinums and Belden Wires. The car ran fine under driving conditions with those in, hit boost and pulled hard without issue. Switched the plugs out for NGK BPR6ES gapped to about .030" and Accel Wires. Car runs the same, but feels smoother through the RPM band. The issue has seemed to tame down ever so slightly but it still happens. I don't believe there is a leak anywhere, reason being I took a can of Propane and a hose all around the engine bay and couldn't get the idle to change. I'm going to look over the exhaust again and see if I can pinpoint the leak. I'm pretty sure it's in the downpipe. Now is there possibly a way it could be the Power Transistor for the coil packs? I did replace one coil pack b/c it had a burn right through it. On a side note, I haven't reset the computer since doing any of this.

 

[miguelmcv]

It could be your transistor as well, But, because the bad idle is not so frequently, It makes me believe that is not the transistor, which it might be a little worst then it is.

But, A common exhaust leak, can give you a lean situation at some point, but can bee accurate at most of the time.

Exhaust Leak is what I would go first.

 

[93dsmwi]

exhaust manifold leak? i had that too dealer told me 450 to fix i laughed.

 

[LxiMax]

Just for giggles today I tested the ISC. It turned out good, all between 30-40 ohms when warm. On a side note, since resetting the computer, the transmission shifts properly now even though you can tell it doesn't want to. New end clutch pack is imminent.

 

[LxiMax]

Tested for boost leak and it held 10 psi no problem. Timing is good. Leaky injector perhaps?

 

[billyw88]

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

 

[volcomsnow245]

I had the exact same problem check your o2 sensor my car idles perfect now but alot of our cars just miss because of old coil packs I would check your timing again though.

 

[kablamo97spyder]

i had the same issue and it was my idle motor...in my opinion however you should not replace just the idle motor as you might see the issue come back in the future..just get a whole new TB with the idle motor attatched

 

[LxiMax]

Been a while since I updated this. Still having issues. ISC tested and replaced, O2's good, ECT reading properly, no boost leaks, no vaccum leaks, TPS within specs. Runs fine under load. Just has a loopy idle. Question, is the ECT and CTS the same? And can the way the Auto trans shift have any indication of what may be going on? First gear shifts quick, then the normal 2-3 small flare, then sometimes goes into O/D at regular throttle. Only time O/D always works is when I'm barely on the accelerator. Thoughts?

 

[92AWDHX40]

How about the brake booster line? Tps, throttle cable misadjusted, throttle body, could need a rebuild, so isc, boost leak tests, check all vacuum lines, found mine with several leaks after i did many tests. How about the egr valvel, check that out.