Have a 2012 Mustang Gt with a manual trans, the idle surges between 500-750 rpms, doesn't matter if the a/c is on or off, does it after running on for more than 10 minutes, took to local Ford dealer, they called Ford and said because it is a manual there is not enough of a load on the engine to keep the idle smooth.
Wondering if anyone has an auto trans that does not surge or a manual that does the same??
Wondering if anyone has an auto trans that does not surge or a manual that does the same??