986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Idle revving 1-2 k after engine swap

Aanic · 05-28-2021, 05:48 PM

Ok, update. New MAF, genuine Bosch unit, numbers match, still having the issue. Everything fully connected, on cold startup the engine shoots up to 3000 rpm then slowly backs down as it warms up. This is on a cable throttle body, so that seems wild to me.

Once warm the engine hunts between 1000-2000 rpm. If I tap the throttle it jumps up and then still just sits high rpm, say 3000 again for a bit. Throttle has returned to normal position at that point but still screaming high rpm.

I've cleaned and swapped the IAC, brand new MAF, coils/plugs. No DTC codes present or pending. This one is getting me stumped. When its sitting at RPM its smooth, no misfires or pings.

If the throttle is closed and the idle is hunting I'd think it woudl be the IAC, maybe its the throttle-valve switch below the IAC? Would O2 sensors cause a wild idle?

05-28-2021, 05:48 PM	#5
Aanic Registered User Join Date: Jun 2018 Location: Portland, TX Posts: 55	Ok, update. New MAF, genuine Bosch unit, numbers match, still having the issue. Everything fully connected, on cold startup the engine shoots up to 3000 rpm then slowly backs down as it warms up. This is on a cable throttle body, so that seems wild to me. Once warm the engine hunts between 1000-2000 rpm. If I tap the throttle it jumps up and then still just sits high rpm, say 3000 again for a bit. Throttle has returned to normal position at that point but still screaming high rpm. I've cleaned and swapped the IAC, brand new MAF, coils/plugs. No DTC codes present or pending. This one is getting me stumped. When its sitting at RPM its smooth, no misfires or pings. If the throttle is closed and the idle is hunting I'd think it woudl be the IAC, maybe its the throttle-valve switch below the IAC? Would O2 sensors cause a wild idle?