: Fuel Problem. TPS or a cleaning?



nas_fan
01-28-04, 04:32 PM
I have a '96 STS 4.6 and it was running with a miss and putting out the engine code "MISSFIRE". I replaced plugs and wires and it went away. It came back. I replaced all 4 coils. It went away again. And, yes, it came back again. I took it to the shop the next day and it ran fine. So I dropped it off anyway and they looked it all over, drove it and can't find anything wrong. No vacuum leaks, nothing. When I picked it up the engine light came on before I got home. This time it's not blinking, just steady. It runs just fine. When I clear it, it comes back eventually. It's the code "THROTTLE POSITION SENSOR LOW VOLTAGE". The missfire hasn't come back just yet. If it's going to do it again, it should be back within a week giving this problems history. Dealer tells me that a cleaning of the fuel system should fix it. Or check to see if one if the injectors are bad. Haven't done that yet. But if it doens't do it all the time I think I could only listen to the injector to see if it's bad only if it's running bad at the time. If the dealer is right, then why would it put off a code for TPS if the TPS isn't bad. It's only about $40 for that compared to over 100 for a cleaning. Anyone have any suggestions as to what I should do to fix it next?

BeelzeBob
01-28-04, 04:45 PM
Check the fuel pressure regulator. Pull the vacuum line off the fuel pressure regulator while the engine is idling. Watch the vacuum nipple on the FPR for any sign of fuel leaking from it......there should be none.

nas_fan
01-28-04, 04:55 PM
I pulled off the vacuum line and no fuel leaking from the nipple.

BeelzeBob
01-28-04, 10:26 PM
I pulled off the vacuum line and no fuel leaking from the nipple.

Well, that is good I guess. At least we know the fuel pressure regulator isn't leaking....LOL

What code is setting specifically? What is the code number?

Unusual for the TPS low voltge code to set on a 96 since that engine had idle air control and the throttle always rests against a fixed stop. If that code is setting I would look at the connector at the TPS to make sure that all the pins are clean and no corrosion. The TPS may need to be replaced if it keeps up...could have gotten moisture in it or something.

nas_fan
01-29-04, 05:12 AM
There were 2 different codes and I called the dealer and they were the same code he said. Code PC1122 and I think the other was PC0122. Maybe the connectors just need cleaned or they got wet cause I had the engine super steam cleaned about a month ago. Looks like a brand new engine now. Maybe something just gotten wet. If that's the case, I hope it hasn't gotten corroded since then. I'll check that next. Thanks alot.

:bouncy:

BeelzeBob
01-29-04, 01:52 PM
There were 2 different codes and I called the dealer and they were the same code he said. Code PC1122 and I think the other was PC0122. Maybe the connectors just need cleaned or they got wet cause I had the engine super steam cleaned about a month ago. Looks like a brand new engine now. Maybe something just gotten wet. If that's the case, I hope it hasn't gotten corroded since then. I'll check that next. Thanks alot.
:bouncy:


Ahhh....now the truth comes out. If the engine was steam cleaned then likely there was moisture forced into the TPS and/or the TPS connector. I would consider replacing the TPS as it is not likely to heal itself and moisture is sure death to it.