New owner, just failed GA emissions, high NOx main culprit

[Merrill]

Mitsu TPS's are very VERY fickle. They need to be pretty much dead on when setting otherwise it will "idle hunt" (revving up and down at idle). It will also throw off fueling and other settings. I usually tell people not to mess with it unless they absolutely have to.

The throttle closed position (0%) is actually a large range. If you don't have it dead on, it will add problems. If you have a bad TPS already, you will just make things worse. The best bet is to replace the TOS and try setting it if you are certain it is bad. The TPS doesn't randomly adjust itself, so if it is throwing a code because the TPS is bad (not in conjunction with, or a resulting code based on another problem), chances are it's just needs to be replaced, not adjusted.

[leftfield6]

So, just to update the thread, I finally gave in and took it to a shop. Here's the word.

• The EGR valve itself is fine, but the EGR solenoid is bad.
• My TPS is bad, it has a number of drop-outs in what should be a smooth linear change in voltage.
• O₂ sensor is bad, it's probably the original one from the factory

The shop is tracking down parts. They have a supplier who says they can get the parts, but they didn't get prices back to the shop before they closed today. I'm expecting this to not be cheap, but I am running out of time to get the vehicle registered. I'm traveling on business the next two weeks, so no way I had to keep chasing the gremlins.

Same shop is also replacing the flex-pipe in the exhaust system.

When all is done, hopefully I will have a perfectly running 90K mile truck!! It will still be ugly, but who cares.