Piston Slap: Fix My Sunfire, Sanjeev!

TTAC Commentator Tankinbeans writes:

Hello Sanjeev –

I have a goofy problem that I’ve run into my mom’s car. She currently drives a 2005 Sunfire, 2.2 auto, and it has developed an irritating tick. When running, the car sounds like a ticking time-bomb; it’s similar to the sound that might occur when you put a playing card in the spokes of a bicycle tyre.

From what I gather it’s related to the ventilation system because if you turn the airflow selector to foot only, all the way to the left, the noise stops. However, when the selector is on defrost the noise is there. This happens if the fan is off and if the fan is on. With the car running I can hear it outside the car clearly, but it’s more clear near the passenger side windshield wiper. If I place my hand at the base of the windshield I can feel the vibration from whatever is causing it.

We didn’t really notice this until she had an aftermarket radio installed. I don’t think this has anything to do with it, but figured more information is better.

Thanks,

Sanjeev Answers:

Who is this Sanjeev guy and WTF is up with him getting into my business? Seriously, since I was a little kid, this has been my second name. I blame my parents for NOT giving me this fantastic name to start. But I digress…

I can’t find a correlation between your stereo and the ticking noise, unless the stereo installer had a REAL hard time getting the aftermarket bits in without mucking up with the HVAC control unit and the big box o’ crap (blower motor, evaporator, heater core, blend door, etc) behind the dash. And anything is possible, for sure. Just for giggles, disconnect the stereo’s new wiring harness from the Sunfire’s factory wiring and see what happens. If the noise goes away, you got a big problem with the installer.

If the stereo isn’t at fault, there has to be something wrong with the blend door system in the HVAC box behind the dash. But that makes no sense, since the noise is independent of the fan’s (i.e. blower motor) operation. Dammit: SANJEEV FAIL.

Perhaps there’s a relay for the blower motor that’s connected to the stereo’s wiring…nah, SANJEEV FAIL.

Have you considered the possibility of badge engineering being at the heart of the problem? Put the stereo in a 2005 Cavalier and see what happens…nope, SANJEEV FAIL.

Sanjeev gives up. Off to you Best and Brightest.