Alright heres the story about the Idle problems...

My car was missing here and there so i decided to do a tune up. So went and bought NGK iridium tip plat plugs, NGK Wires, a new distributor cap and rotor, new upper intake manifold gasket, and new throttle body gasket and replaced all and put her all back together. Started up and she purred no missing idle was perfect 700-800 rpms. Drove down the road stopped at the stop sign... Died(my car is a manual so when i put it in neutral it died.) Brought it back home and shut it off check if everything was connected and put together right (vacuum lines ect, which everything was perfectly fine.) Start it up and jump to 400 RPM and wouldn't keep an idle. So i was told it was an IAC valve gone bad. So i went and bought one (like $200+ later brand new OEM valve) replace it and now idle is NO LESS than 2k RPM's. And after going into gear, then back into neutral, the rpms jump up and down (as show in the video below) from like 1200-1600ish while im rolling, then when i stop it goes back to 2k for a second, drops to 1k slowly then jumps right back up to 2k again. Then the process repeats itself.


Things i have replaced trying to fix the problem:

1. iac valve $200~
2. upper intake manifold. (a shop told me my stock one was warped?) no worries though it was cheap.


Things that make the idle perfect again:

Unplugging the MAF sensor ( i have a cold air intake, the problem isnt because of the CAI though it happened after i did the tune up not after i put the CAI on)

Putting the defroster on (it will sometimes make the idle go down back to normal, sometimes it wont work its weird)

Any ideas what this could be? im totally about to just buy a new engine and say fuck this stocker and swap it out. (found *** engines free shipping about 650-800$~)

Here's the video.

https://www.youtube.com/watch?v=kMPivpDmL1A&list=UUDClM6s3QJ6cOnUPpG0fdXQ

My guess is a vac leak hard to tell when u can't listen to engine. Removed everything you taken out and put it back together with proper torquing sequence.

Sounds like you need to do an iac relearn procedure. Unhook the battery for a few hours. That may reset it to default. If not google the procedure for your model. Most are pretty simple. Check the throttle body for buildup that could hang it open. It doesn't take much to raise the idle to 1600. Since replacing the iac caused a change it's likely that was the problem. You could have pinched a gasket though. It's hard to say.

This post was edited by FMX_89 on Aug 12 2014 08:10pm

thats what everyone says "huge vacuum leak man" yada yada yada. Well i'd be able to hear the vac leak if it was that bad, ive sprayed carb cleaner EVERYWHERE and idle does not change at all. Even tried the cig smoke trick. That doesnt work as well. so im assuming its something else than a vac leak.



ive cleaned my throttle body down to the metal lol no carbon in there AT all. (well im sure there is some buildup now since ive been driving it a bit like this) but i may try to unhook the battery a few hours (if thats what my car requires ill google it in a second after finishing this reply) but yeah thanks guys for the fast responses. Ill keep everyone updated if the battery unhooking fixes it.

Gm stuff requires you to start it from cold and let it idle for 10 min for the idle relearn. Just an example.

ive googled it and a lot of pages ive viewed require the Battery to be unhooked. ect. ect. then drive for 20 mins without ac/lights on.

This post was edited by HeavensAngel on Aug 12 2014 08:33pm

you can hook a computer up to it and read what it's doing to help
Get a better understanding if there is an issue and your
Engine is trying to correct itself


Sounds like it's time to do full clean sweep.

Heads, coils, wires, distributor cap and rotor. Timing belt.

I love my eclipse and it almost does the same thing.

But i am waiting until i get my taxes to drop money into it.


This post was edited by TwinCities on Aug 13 2014 10:59am

To elaborate on this anything that will show live obdII data can show you STFT (short term fuel trim) and IAC steps (think of the iac as a valve with over 100 positions from open to close). If it's requesting the iac to close off and the rpms are high you have a vac leak. If that happens and you have a high stft % the vac leak is unmetered, meaning it is downstream of the MAF(if you have one.) If the trim is under 10% it is metered, which points to the iac or throttle body blade.

If the iac needs to relearn your iac valve is open farther than it thinks it is because of the new sensor. A quick way to test it without a computer is to warm the car up, shut it off, remove the iac valve, and plug it. If the rpms drop way down or it idles normal the iac is likely in the wrong position.