My car makes a funky ticking sound but only when revving down from 2500 rpm to 1000 rpm. The frequency of the tick is proportional to the RPM, but not nearly as fast. It sounds like a 10 speed bike freewheeling or maybe the reel of a fishing line spooling out. It's coming from the area of the turbos, but I can't isolate it. It's pretty loud. Does not happen under acceleration, crusing, boost, etc. Only when I'm slowing down to stop or free revving the motor. The sound occurs with or without the clutch in, in and out of gears. The frequency is too low to be from a turbo wheel, I was thinking a vacuum leak but it's really unusual sounding for that. Any ideas? Thanks!

 

unplug the connectior for the airpump, see if the noise persists.

if it goes away, more than likely your airpump is shot.

 

Sorry I should have mentioned I have already replaced my airpump and the problem persists even when it's (new pump) unplugged. The bearings on my old pump were totally shot after 75k miles.

 

Anyone else have any ideas? I'm still stumped.

 

It could be a sensor failing. Maybe the ISC solenoid? Have someone rev the car in the proper rpm and try to pinpoint the sound. I know this sounds funny but a long tube (piece of pvc) and stick it up to year ear and move it around the engine bay. See if you can isolate the location of the noise. It works. G

 

Does the tick ever occur at idle? Does it sound like it's coming from behind the gauges?

 

It could be the ISC, we had the same issue with his, only it wouldent difference was that it would die at stop lights, turned out the ISC was bad.

 

Possibly an exhaust leak... check the basic stuff first airpump, exhaust, etc

 

i have a ticking sound on decel and it was determined to be my wastegate.

 

bump. i'm having the same problem. any solutions?