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

blue62 · 05-28-2021, 07:19 PM

Interesting that when you unplugged the MAF before you reported a steady idle at 700-800RPM but now if you unplug the MAF it is a rough idle.
Also now you have miss fires that you didn't have before.

I am still leaning towards intake air issues.
vacuum leak, MAF, IAC, or the throttle valve switch you mentioned.
Vacuum leaks can cause misfires but they are usually random not just one bank.

The only other thing I can think of is since this is a replacement engine.
Is the replacement engine the same year as the original engine.
ECU/DME compatability issues????

05-28-2021, 07:19 PM	#9
blue62 Registered User Join Date: Aug 2018 Location: Woodland Wa Posts: 1,300	Interesting that when you unplugged the MAF before you reported a steady idle at 700-800RPM but now if you unplug the MAF it is a rough idle. Also now you have miss fires that you didn't have before. I am still leaning towards intake air issues. vacuum leak, MAF, IAC, or the throttle valve switch you mentioned. Vacuum leaks can cause misfires but they are usually random not just one bank. The only other thing I can think of is since this is a replacement engine. Is the replacement engine the same year as the original engine. ECU/DME compatability issues???? Last edited by blue62; 05-28-2021 at 07:24 PM.