Hey everyone, recently my 2.2 has had a god awful idling issue. When I stop at a light for instance, the engine shakes and shudders for a couple seconds. It sounds like the engine revs up a bit after it shudders but the RPMs don't change. Idle RPM is around 800. It acts like it's going to stall and I know it can't be any good for the engine. I swear it's worse when the car is warm. I don't notice it when I first start driving.

I cleaned out the TB a few months ago and switched out the MAF to fix an issue I had with sluggish starts. It starts like a champ now but I swear the issue started happening around then, but not as bad. I didn't touch or move the butterfly valve at all so I know it's not that.

Two days ago I put in a new fuel filter and checked the spark plugs (Bosch pre gapped, about 5 months old) and there was some dark liquid on the threads. None on the top half of the plug, no oil pooling up there and no leaks in the valve cover gasket. JUST on the threads. I couldn't tell if it was oil or gas. I read that liquid on the threads might mean running rich. Could that be a contributor to the rough idle?

I have a K&N CAI that I cleaned pretty recently too.

Other than the idle the car runs and drives great. 82k miles, meticulously maintained. WTF

What do you guys think?

 

https://ngksparkplugs.com/en/resources/read-spark-plug

No CEL or codes? How's your MPG? Does it stumble and run rough immediately after starting (these/most cars start using VE and then the MAF takes over)?

 

If it is an automatic, does putting it in neutral change the behavior?

 

No CEL, no codes. MPG is as it always is. I get around 22-23 in the city and high 20s low 30s on the freeway.
Doesn't run rough after start, feels solid. It starts to stumble after its warm when I stop.

edit: just saw your spark plug link. I'll pull them out again today and take a look. From memory I'd say they look like the normal photo with maybe a bit of the second "wet/dry fouling". Not worth much, since I've only changed spark plugs once, but when I pulled mine out to check they seemed dirtier than I would expect. But then again, I haven't changed plugs more than once.

 

Yeah it's an auto. Putting in neutral seems to lessen the intensity of the stumbling a little bit but not entirely. I'm not 100% sure, but I don't think it stumbles in park. I'll have to test that today.
82k miles on the oem trans fluid, although I don't think that should have any effect on what the engine has been doing. I'm changing the fluid soon anyway.

 

Bump

Anyone have a clue ?