Last week, we took our 2007 Mustang GT/CS into the dealer for diagnostics on a thumping sound coming from the intake area. To help you imagine what it sounded like, when you empty a plastic gallon milk container leave the cap off and give the bottom of the container a good strong tap with the back of your finger. Here's a video/audio of what it sounded like:
The dealer could only go so far with warranty work since we have an after market Throttle Body (TB) and Cold Air Intake (CAI) installed, but they did put the car on the computer to check for problems and didn't find anything wrong. Interestingly, along with the thumping, after revving the engine idle hangs at about 1,100 RPMs. The night before, when I dropped the car off, Brian (our service writer) who is pretty sharp took the time to discuss the problem with me and had his head under the hood listening to the thumping. His quick diag suggested that the TB was opening and closing at idle prompting him to think that the TB or something in that area could be the problem.
I brought it home, removed the CAI, cleaned it up the TB, and took it out for a test drive. The thumping seems to be gone, but now the throttle sticks when in gear after acceleration. I double checked that the TB is throughly clean and the butterflies open and close as they should. I also verified that there is no play in the butterfly shaft.
A bit more on the sticking - When I let off the gas, the car continues at the same RPM and speed. If I push the clutch in, the RPMs stay high for about 3 - 4 seconds then come down very slowly. I checked the carpet around the gas pedal to make sure nothing is in the way, but this wouldn't be the problem since the throttle only sticks when in gear. I am not sure if cleaning the TB had anything to do with this new problem of throttle sticking, but my thought is that it's coincidence since it just recently started sticking at idle and the problem might have been progressing without my assistance
With the exception of the idle coming down to around 1,100 RPMs after rev and the sticking throttle in gear, other functions seem to be normal. Some research on the Internet found that others have had throttle sticking issues (stock and aftermarket TB's) since 2009 with V6 and V8 electronic TB's.
Since the stock tune was still in the car, I re-flashed with the custom tune (done by Ray McClelland - Full Throttle Kustomz) but that didn't correct the throttle sticking so, I re-flashed the stock tune back in. Something I did notice though, after putting the stock tune back in the engine was mis-firing at idle, which seemed to clear up after running for a few minutes and a couple of revs.
Today, I'll check the Throttle Positioning Sensor (TPS) voltage to make sure the plunger is adjusted correctly. If correct, I'll reinstall the factory TB and retest everything. If the problem still exist, the car goes back into the dealer for warranty work.
I'll post an update when I have more info.
Anyone have any ideas?
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