Idle surge when ac is on - Ford Mustang Forum
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post #1 of 3 (permalink) Old 09-13-2019 Thread Starter
Dalton2006GT's Avatar
Joined: Dec 2017
Location: Augusta
Posts: 70
Idle surge when ac is on

I have a 2012 mustang gt that surges at idle when the ac is on. It sits at about 750 rpm at idle and drops to 550 rpm when it surges and comes back to 750. I have cleaned the throttle body when I installed the 2018 manifold, I also cleaned the maf when I installed the PMAS CAI. It's been doing this since I bought the car when the dealer said they put a new compressor on it. When I bought the car it was bone stock besides exhaust and being lowered. Whenever it surges, it's shakes the entire car I'm thinking this may due to the poly motor mounts. Mods are, 2018 manifold, pmas CAI, cat back, and a Lund tune

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2012 Lava Red GT
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post #2 of 3 (permalink) Old 4 Weeks Ago
Clevernamehere's Avatar
Joined: Apr 2012
Location: sarasota
Posts: 31
I have this same exact issue and have ruled out anything related to the intake. Has something to do with the actuator and the ecu sensing the AC load

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post #3 of 3 (permalink) Old 4 Weeks Ago
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JBert's Avatar
Joined: Jan 2011
Location: Central Massachusetts
Posts: 8,960
the poly motor mounts do tend to exaggerate vibrations and other things so that might have something to do with it . . . some idle variation is "normal" as the A/C compressor kicks on and off but yours does sound a bit more than "normal"

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