I got a 99 Trans Am with a vic jr and accufab intake set up currently getting tuned at a local shop, today they called and said when the key in the car is on the ON but the engine is OFF position the TPS reads fine, but when the car is RUNNING the TPS bounces all over the place. Any ideas on what could be causing this? I had to extend the wires for the TPS but i double checked those and they are just fine. I read in another post that the MAF sensor could cause the TPS to act up, Wondering if this is true or if anone has any insight on this problem

 

Are all your grounds clean and tight? These things need to be grounded properly. Go overboard....engine to frame, engine to battery, engine to body, some even do engine to trans, but thats probly overdoing it. Id start by checking the grounds. And make sure the alternator voltage is stable right at the alt terminal.

 

Don't know what "all over the place" means but a
crusty old sensor could just have a bad wiper or
a worn spot where it's rested and chafed the
resistor stripe. Put the meter to it and see if you
can induce intermittent behavior by wiggling the
throttle. Also look for "flicker" on the +5 to GND
wires close to the sensor, in case you have an
upstream intermittent.