Just had an independent mechanic replace a valve cover gasket and change plugs while in there. 101k miles on the car. It ran great before this work, but knew the gasket had to be done and with that many miles on it did the plugs as well. Now the car runs a fast cold idle at about 1600 rpm, then down to 1200, and finally to about 750 at warm up. When on the road after warm up it idles rough, almost like timing is off. Never did this before this work was done. First suspect was vacuum leak, but called the guy back and he checked it all. Said he found a small leak and fixed it, but no improvement. He was willing to make it right, but didn't seem like he knew what to do. Any ideas out there on what could be wrong? Could an electronics wire be undone or misplaced? Could the throttle body gasket need replacing? I also note the smell of gas around the car in the garage after returning home. Could he have nicked the plug gap when installing plugs? I provided the plugs - Denso iridiums. I usually do a lot of the work myself, but this time I had someone else do it. Any ideas what I can check to restore normal smooth idle?? Thanks.

 

Have you tried the basics - unplug the negative from your battery and reconnect after 15 minutes? Might reset any ECU issues or need to relearn idle (doesn't seem like it would be related but might help).

 

Thanks Sampak. I'll give it a try. You never know.

 

What happened how did you fix it