Stange idle problem

[Charles]

Originally posted by Flight 951
I recently had a throttle position switch act up on my car. One day, the idle started fluctuating between 1200 and 1800 rpms consistently. Vroom. Vroom. Vroom, at stoplights.

That happened to my 944 about a year ago... turned out to be a temperature sensor issue. The sensor in question is near the throttle body, so if the wires are loose, vibrations could affect the connection.

Apparently, the electronics in the TPS go bad, and you may be able to check this by popping the hood and tapping firmly with your finger on the TPS while the car is acting up. My car stopped doing this after I tapped it. I'm now waiting for a new TPS now, since I guess the old one was on its way out. My car has 82k miles. Hope this helps.

The TPS is nothing more than a switch. No electronics to "go bad" in the usual mysterious sense-- but the contacts can get fouled up, or the switch could be misaligned. All you need to check it is a multimeter, and the message archives have a number of different takes on how best to test it.

[robm-951]

The TPS is nothing more than a switch.

On a Turbo, the TPS consists of a potentiometer also to provide throttle position along with the throttle closed switch.

Rob