I'm just beginning to see a regular problem emerge. When restarting the car (60K) when it's warm, the engine will start right up and then the rpms will drop to almost 0 and then catch and run fine. No other symptoms or lights. I looked for similar issues but had no luck in the archive. Anybody dealt with this one?

 

Oldmots -You bet I have - I have been trying to figure out what causes this ever since I got the car. My problem started like you describe. Then it progressed to when I put AC on or any strain on the engine - idle will drop and come up again. Latest it is doing it when I draw to a stop. It is a vacuum leak somewhere. Dealer cannot find anything wrong - I think they are using their scan tool and that is it -no codes at all. I think it is the purge valve in the emission system that is leaking but I am not sure - I am in the process of investigating - my car can also be hard to start after I have filled it up - previously after filling up it just seamed to run a little rich when you started it. It has been a very frustrating process that have taken a great deal of joy away.

 

I had something similar. Starts and then almost dies when warm. It actually died a few times. It would also have rpm go up and down on traffic lights. It was a vacuum leak around the throttle body. They said there isa TSB of some sort for it, replaced the clamp with allegedly new model. Looks the same to me, but works fine.

 

In my car it is so clear (as water) that it is a vacuum leak and it might be as simple as what Veffremov is suggesting in your case. I have tried to replace clamp at the throttle body based on Veffremov but to no avail in my case - I have sprayed the whole engine bay with carb cleaner no exterior vacuum leak. Together with the hard start after fill up I think it is the purge valve - I will either just change the purge valve and see or have a smoke test performed.

 

Veffremov - did you ever get a code when the car stalled on you? - according to my memory your car also had problems when the AC was on?

 

The dealer said there was a pending code meaning "Mixture too lean", but I don't recall the number. The AC was making it worse for me

 

My car is running lean at idle - vacuum leak - dealer has confirmed, but no codes. But when I have filled up the next time I start, it is the typical symptoms of running rich I have - which is why I believe it is the purge valve. I hope the car would give a code - I guess first when it stalls and rolls over on the side. BTW it is by fare not the first car I have owned that did not leave a code when something obviously was wrong - lovely when the dealers relies so heavily on their scan tool

 

I have thought about the problem and dismissed a vacuum leak since the car idles so smoothly I can't feel the engine running.
My thinking has gone to a bad temp sensor or ECM software issue. If the temp sensor gives a spurious cold signal on hot restarts, the engine could overfuel and then the MAF catches it when the motor gets running. I'm not sure of the temp sensor thing since the car is averaging 29 MPG right now, if it were telling the ECM the engine was cold, the fuel mileage would drop a lot. Just not sure yet. Thanks for the ideas.

 

Another thing I have considered since this really is sluggish fuel/air mixture control is the pre cat O2 sensor(s). I have replaced my MAF no impact!

 

Does anyone know how easy it is to get to the front O2 sensors?

 

Well, I might have solved it. Since the problem has gradually snuck up on me, I discounted any mechanical breakdown or leak as too sudden for the symptom.
The fuel filter was due to be changed 1000 miles ago so I changed it today. Nothing unusual came out of it but the problem has not returned after a dozen warm starts. I was suspicious since the behavior seemed like fuel starvation, it may have been.