Has anyone had this problem? My Evo is warmed up and at operating temperature. The idle is good all the time. But right after i rev it to 4k rpm's+ and let off the throttle, the idle drops below 500rpms. At that point the car sputters/shakes and takes 3-5 seconds to regain its regular idle rpm. I'd say 1 out of 10 times the car doesn't regain regular idle and just dies because idle drops too low. Any idea what the problem could be?

 

Sounds like your MAF sensor is trying to find idle. Check to see if it's dirty/theres a leak?

 

boost/vac leak maybe. i used to have a coming to stop problem with idle where it will drop low and sometimes stall, sometimes catch. then, i changed out my stock 9 bov to my turbo xs no diaphragm bov and it hasn't happened since. people kept telling me it was the tune but why isn't it happening with the new bov. anyway, back on subject; try cleaning the maf and do a boost leak test first.

 

Forgot to ask. Did you do anything you remember to instigate this to start happening? Or did it all occur all of a sudden for no reason?

 

I removed all the hoses/sensors/screws attached to the top of the intake manifold to clean/paint it without having to remove it. I also removed the uicp to clean it and paint it as well. Was tidying up the engine bay. Should i use regular maf cleaner to clean it up?

And there's no boost leak im sure. If there was wouldn't the idle always be rough?

I don't know when this started happening though, never bothered revving the car before, just decided to show off to a friend after it was clean, with me getting a bit embarrassed after doing it haha.

 

Double check to make sure none of the hoses have any cracks in them. You never know. Also double check the couplers on the UICP; maybe one of them slipped off a little

Regular maf cleaner will suffice. Report back with what ya find!

 

Did you really fill up the system to your boost target level and waited a few seconds? It's the ONLY way to be sure.

 

Had a similar issue with mine.
I ended up having leaking throttle body seals and a loose coupler on an intercooler pipe.

Fixing the leaks and cleaning the maf fixed my idle drop issues.