Slow throttle return

[FoxGT87]

My mustang is having an issue with slow throttle return, i will let off the gas and it will get hung up in the low 2,000r's for a coupple seconds. when it is cold sometimes it will hang up in the 3 grand range if i smack the throttle hard, i have only noticed it a coupple times in the driveway. i was wondering if it was censor problems or if it could be an after market timing chain. i wasnt the builder of this engine, so im not sure what all is going on in the internals. im hoping its just censor problems cause my tranny grinds pretty badly in second gear and has problems with third sometimes aswell. the only way to not get second to grind is to go slow, granny shift, wait til the throttle returns back to idle and shift. with my 4:30 gears commuting sucks! help me!

 

[bmo37]

My first guess would be you have a vacuum leak some where. check all the lines for cracks, and check around the upper and lower intake as well.

 

[Celeb]

+1 for a possible vacuum leak. If you don't see anything visually, start the car and spray some carb cleaner around your vacuum hoses and manifold and listen for the idle to raise indicating the car has "ingested" the spray.

Might just be a hose popped off.

 

[dcurtis]

+1 for a possible vacuum leak. If you don't see anything visually, start the car and spray some carb cleaner around your vacuum hoses and manifold and listen for the idle to raise indicating the car has "ingested" the spray.

Might just be a hose popped off.

+1 on possible vacuum leak.

 

[HISSIN50]

If it happens in the driveway, you can try disconnecting the electrical connector to the IAC and see what happens (don't drive the car with the IAC disconnected. It could stall at any time).

If it falls down to ~600 RPM immediately, you've found your issue. If it stays at 2-3K RPM, you have not (in which case, keep lookin for the vac leaks the guys mentioned).

 

[BYRDPE]

Have you tried a base idle reset?

Posted via Mobile Device

 

[spoulson]

I recently located a few sources of vacuum leak in mine. The previous owner had installed a mismatched upper to lower intake fastener that loosened, causing an air gap in the gasket. Also, the PCV managed to pop out of the lower intake and made for severe drivability issues. Additionally, I found that the lower intake manifold fasteners had all come loose and sprang a coolant leak, and probably contributed to more air leakage.

 

[FoxGT87]

i got some spare time this weekend i will be pulling it out and checking for vacume leaks, and tell you all how it goes.