Originally Posted by CFbabe

CFBabe asked me to draft this post since I'm the gear head B/F.

This has happened 3 times now ... the last two happened today while I was driving the car. The circumstances were similar all three times; those being:

a) It was hot weather -- 80+ deg F.
b) I had stopped and parked the car for 10 to 15 minutes after I had driven it quite a while, so the engine was fully hot.
c) After getting in the car, starting and driving for about 5 to 10 minutes the engine would idle so rough that I though it was going to die.
d) The engine would hardly respond to any gas pedal ... acted like it was going to fall on it's face. Once it started picking up RPMs, it would surge and hesitate until about 2000 rpms. Seemed to be running way too lean IMO -- usually surging is associated with leanness.
e) Never saw any "Check Engine" light come on.
f) Shutting down the engine and restarting did not seem to help. Thought maybe the computer went into "limp mode" for some reason.

Did a search on the board and only found one other instance of rough idle, but there was nothing said about the engine hesitating and surging off idle.

With extended driving after the car gets into this mode, it seems to slowly come back around, but still somewhat hesitant off idle when first moving off from a stop light for instance.

Anyway, it seems like it's hot weather induced, possibly something getting heat soaked under the hood since it only seems to do this after sitting for 15 to 20 minutes after shutdown. Strange thing is that it takes 5 to 10 minutes AFTER starting it up and driving before it goes in to rough running mode. Seems like if a sensor or if the fuel lines were heat soaked that it would run rough right after a heat soak period.

Anyone here experience this phenomena? I suppose the dealer should scan the computer to see if any trouble-codes were set by the ECU, but wanted to see if the board knew any info at this point.

Originally Posted by BRappaport

I had rough idle problems on and off as well...and then my check engine light came on after a few weeks later...I took it to the dealer...he read the codes...no new codes...but there was an old code stored that pointed to a bad air injection pump. In the very front of the engine...there is an electric driven air injection pump...which injects air into the intake...sort of like a choke to lean out the mixture. You could feel air coming out of the pump where theirs a gasket...pump should not have any leaks...this was replaced and solved the check engine problem and the rough idle...but its only been a week since the replacement. I will give an update in a couple of weeks. Hope its fixed for good!

Originally Posted by woody

Glad it solved your problem but just a correction on the air pump statement. The pump actually injects air into the exhaust manifold via the cylinder heads, not the intake. Its to help raise the temp of the cats during warm up.