Immediately after the engine starts, the RPM seem to creep up to idle, almost the opposite of what it used to do where it would start higher and quickly settle lower. I am referring to the period of a couple seconds immediately after starting the engine. This change began a few weeks ago after having trouble starting the engine, where it took several attempts to get it started (engine cranked well, but wouldn't start). Now the engine starts quickly as was usual, but with this brief creep or lag in the RPMs to reach idle. Any diagnosis?

Only potentially relevant mods are a PRM intake and small Hawker battery, both of which have been there since the car was new ('03 with over 16,000 miles).

 

My guess is the ambient temp at engine start.

 

Dave, it happens even when I start cold in the mornings. It starts easily and no stalling, so it's more just a curiosity at this point as to why this change. The car feels the same performance-wise. I am just hoping it's not the beginning or a sign of something more significant to come.

 

Did it happen before you switched back to the stock exhaust? Have you tried resetting the ECU? Map whack?

 

Yes it started happening several weeks ago, and I have pulled and reinserted the fuse for the ECU, but not whack the MAP. Maybe I'll try the MAP whack. I thought it might be a loose hose or something, but everythings looks normal.

 

Look into the Idle Air Control mechanism. It's located on the driver's side of the intake manifold and has those little black rubber "U" shaped hoses on it. It has been reported that the solenoid and go back. In the two cases, I've seen reported, that solenoid makes a repeated clicking noise like it can't quite cycle fully. Ordinarily, as you've already stated, after a cold start, the idle should be a bit higher and then settle down over the next couple of minutes or so.
However, do the MAP whack and ECU reset first.

 

Thanks all. I'll try the suggestions and let you know.

 

It's now back to normal after doing a MAP Whack and resetting the ECU. Thanks guys.