I've gone through all the posts and many weren't updated. I'm hoping there is some new news on this topic. Here's the issue and all that's been done.

Car hunts for idle +/- 200 RPM. Sometimes intermittent. Sometimes constant. In neutral its fine. In drive it has the problem.

Replaced all plugs and coils - just fixed a code. No improvement for idle
Cleaned MAF - fixed it for a few days
Had valves walnut blasted - fixed it for almost a week
Dealer played with intake hoses to MAF - fixed it for a few days
Replace air filter - nothing
Timing chain replaced
Fuel pumps replaced

I read in one post on a Euro car replacing the solenoid valve fixed it. Otherwise just frustrated posts.

I'm at a complete loss and now the dealer who spent a lot of time on it I think is giving up. The car runs fine. Its just has this tick of an idle which is maddening. I always complained when we bought the car new it had a stumble at idle but the dealer couldn't figure it out. Now we live in a colder climate and its worse.

Help.

 

throttle body cleaned? excess oily build up in/around the throttle door will cause idle issues

 

Is that related to the airbox? Trying to see where that could be to check it. I would've hoped when the dealer did the walnut blast they would've inspected that. It was only done a couple weeks ago.

Thanks for the suggestion!

 

you dont need to remove the manifold to do it, but if it was out for walnut blasting it would make it easier to do. the throttle body attached to the intake manifold on one and the other end the airbox inlet

 

I had this issue for almost 40k miles and no one could find the source. It was present intermittently when in gear at idle but would always show up when slowing down to come to a stop. The idle would dip really low then fluctuate for a bit before returning to idle.

it turned out to be a small vacuum leak. After a few weeks of back and forth with the warranty folks, the dealer changed the vacuum pump under warranty.

 

That is very interesting. I haven't heard that before. I'll definitely pass it long to the dealer when we take it in again. I'm trying to get all ideas from people who have had similar so I can offer something to the tech. Thanks for the info.

 

yes. it never threw a code. that was the part that was hard....the dealers usually will not take action on changing a part unless they have a code.

I also had all of the plugs and coils changed/ compression checked / top end looked at/ etc. previously.

 

Yes, no codes thrown and they ran test after test, etc. But it hunts like a vacuum leak but its so intermittent its hard to diagnose. Sometimes like the last time it was constant but now its back to intermittent but maddening when it does. And dangerous if it does it when parallel parking as it will surge.

 

I never had my car surge so it may be a different issue. However, it is worth looking into as a failed vacuum pump usually leads to replacing the engine.

 

maybe a funky vacuum hose? It seems when they screw around with the intake it goes away for a little while then comes back. No thanks on replacing the engine We've dumped a lot into the car recently and that would be scary. I'll mention it for sure. The surge is just letting off the brake and the idle changing so its a small but unexpected surge.

 

a failing o2 sensor can cause this as well, and failing o2's don't throw a code sometimes.