I have a 2009 mustang GT California Special with the regular 4.6L 3 valve v8 with 140,800 miles. It has a standard transmission. I currently have Ford Racing fuel injectors, Accel Coil packs, Roush cold air intake, ford performance timing kit, SR performance long tube headers, Catted Borla Stinger exhaust. 3 weeks after purchasing it in August of this year, I noticed the vehicle started to drop to 500rpm, sometimes lower when I take my foot off the gas pedal and immediately or seconds later engage the clutch. It acts as if it is choking out, but it never stalls. As soon as I come to a complete stop it returns to normal idle. Even when I rev the car in neutral sitting still the idle drops, vibrates, then catches back up to normal rpm. I reset the bad tune (it did the idle drop with the tune) from the previous owner back to factory computer settings. Is there a tuning issue or a possible sensor malfunction?
well you didn't mention it at Ford racing injectors and stuff realize you start putting all that stuff on you've changed the parameters of the air fuel mixture and only a real pro could ever tune that thing correctly could do the obvious things like cleaning the throttle check or vacuum leaks and that but if all that's okay you might need to see a real expert Ford V8 tuner to set it up right
