TomKattt

I have a 2002 Impala LS with the 3.8l V-6. Last night I stopped at the grocery and when I came out and restarted the car, something under the hood seemed to pop and there was a little cloud of smoke. After that the car ran fine except the idle seemed to get lower and rough; enough that I felt I had to put the car in neutral and give more gas at traffic lights to keep it from stalling.
I wasn't far from home so I parked the car and haven't driven it since.

I plan to look at this on the weekend, but thought I'd ask for advice first. It was dark and I haven't looked under the hood; maybe the bad component will be obvious, but I would like to ask people's best guess what is likely to be wrong since it will help me on the weekend. The engine light is not on and the gauges looked normal. My best guess is the Idle control valve but I really am just guessing. I would appreciate anyone's ideas. Thanks.

Frank3

I don't know if this applies to your 2002 Impala, but on reading your original post made me think of a couple websites I ran across where there would either be a puff of smoke or a shattering upper intake due to a fuel injector leaking and flooding the intake after it was shut off. A simple backfire detonates the residual air/fuel left in the intake on startup from the leaking injector. Like I said, this doesn't necessarily apply to your Impala but could be worth checking out.

TomKattt

The problem occurred again in June. I dug around a bit and replaced the Fuel Pressure Regulator. It looked like there was a chunk of broken o-ring in the old one and I think that allowed fuel vapor to get up into the vacuum line and into the manifold. This improved the idle and I think it will keep the little explosions from recurring.