2G Rough idle after it warms up

[Milo 92]

Hopefully someone can help. My 99 Eclipse GST idles perfect when cold but after it warms up it starts to stumble. Feels like the car will die but then it idles up again and keeps doing that. It’s never completely shut off. Car is all stock. I’ve tested different sensors and replaced a few things but nothing has helped .

 

[dwb]

That's called idle surge and is super common on DSMs. I would guess a boost/vacuum leak, missing/misadjusted/leaky BISS, bad ISC, or bad FIAV. If you haven't reviewed this, then this would be a good start: http://www.dsm.org/how-tos/tttt/tttt3.html

 

[Havocf6]

Hopefully someone can help. My 99 Eclipse GST idles perfect when cold but after it warms up it starts to stumble. Feels like the car will die but then it idles up again and keeps doing that. It’s never completely shut off. Car is all stock. I’ve tested different sensors and replaced a few things but nothing has helped .

I have similar issues, Does your car surge when cruising at all? Mine will surge and at times feel like its dragging an anchor. I am stock as well.

 

[Jonko]

Hi from down under,
In my experience there are several things that can cause this and not just one alone. Heat & electronic parts don’t play well together; especially when they get tired. I agree with DWB above. Get yourself a garden mist spray bottle and fill it with water. Get the car warm. Identify all inlet gasket mating areas to your cylinder head. With the engine idling spray a steady stream of water (not mist) on the identified areas one at a time. If there’s a leak, the engine revs will change noticeably. Remember to do one area at a time then move to the next area. Once you’re satisfied there’s no change, time to move on. If there’s a change, time to remedy the leak. Avoid spraying your turbo body (of course). I know that coil packs have a tendency to behave the way you’re describing. Once they get hot, they can give an inconsistent or poor electrical supply required. They give some power, but not quite what they’re supposed to. Once again, it can be several things, but sometimes it’s quicker to get it diagnosed by a trusted and properly equipped mechanic to do the things you want to do with your car. I hope this helps.