Engine Rough Idle at Start, Possible CMCV Vacuum Leak


New Member
Apr 4, 2019
Wilmington, DE

I have a 2015 salvaged coyote in a 67 mustang running on the control pack. Everything is up and running, but it seems to have a rough idle at start. The idle continues to be rough until I rev the engine and it settles down to normal at around 1000rpm for about 5 seconds, after 5 seconds the idle begins to rev up similar to a vacuum leak on a carburetor and is not consistent. The more I rev the engine the better the idle gets and continues to idle correctly for longer. I have a feeling it is most likely a CMCV vacuum leak but I guess it could be a stuck throttle body or faulty ground to the accelerator pedal sensor. I also totally winged the vacuum plumbing to the CMCV's based on a forum I read because I am not using a brake booster.

Here Is the thread :
https://thefactoryfiveforum.com/sho...tion-Regarding-2015-2016-Coyote-CMCV-Plumbing )
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