rustbukt307

Hi everyone, looking for help once again. Experiencing a check engine light every so often with my Olds 307 in regards to a code 21 being thrown. Typically happens at a stop after I've been driving for a while, like coming off a highway off ramp for example. It's also much more likely to happen if I'm running the A/C. My service manual tells me it's a TPS related code (signal voltage high) and can happen for a few reasons including an idle speed of less than 750 rpms.

Anyone have any suggestions on what to look for to help remedy the problem?

joe_padavano

The TPS is simply a rheostat. Since the wiper wears against the wires in the sensor every time you move the throttle, it eventually wears out. It likely needs to be replaced. Note that you may need to adjust the TPS after replacement. The CSM shows how.

rustbukt307

If the TPS is at fault, wouldn't the code be constant if so? It seems like it's throwing the code 21 because the engine speed at that time is less than what it should be based on the throttle position. So this causes the ECM to throw the code. What would cause my idle to dip like that when at a stop after some travel at cruising speeds?

joe_padavano

Not at all. The wiper is constantly moving on the grid. Sometimes it makes proper contact, sometimes is doesn't.

m371961

I am only commenting here to try and learn more, not to interfere. This is where I, (the unknowing) would just drop the money down and buy one. Does the CSM show any troubleshooting as far as reading ohms across the sensor range and a test procedure? If it does, then I would try to simulate the failure, but that may be hard to do.
This is what bugs me about electronics and where I end up doing the best guess replacement.
Teach me something and let us know what you find.

olds 307 and 403

The TPS absolutely can cause a dip in RPM and hesitations while driving. Check the TPS with a volt meter, it should have 5 volts at one wire, another is ground and the signal wire should read around .5 to .75 at idle to about 4 to 5 volts full throttle, with a smooth steady climb as you move the throttle. The tests are all with the key on, not running.

rustbukt307

I'll have to throw a meter on the sensor itself and see what it's reading. I noticed it hunts at idle and it throws the code 21 while that's happening. It also seems like the ILC isn't doing it's job as it doesn't move when the A/C is turned on in either Park or Drive. The hunting at idle happens regardless of what the A/C is doing.

Seff

You can check the sending unit for "dead spots" with an oscilloscope, where dead spots will be far easier to spot (open circuit spots). Same goes for a fuel sending gauge, for that matter.

rustbukt307

Ordered a new TPS by Airtec/Wells from Rockauto since they had one left at a $16 price, as well as a new connector for my M/C solenoid since it's broken and held on by a rather ghetto ziptie fix. How challenging is it to set up a TPS?