Would a bad TPS cause my teg to fail emissions without throwing a CEL?

The reason I’m asking is until last weekend I never threw a code for my TPS. Over the last three years (since my swap), I’ve had problems with my idle and have been unable to pass emissions and tried everything in the book short of replacing the TPS to correct these issues (complete tune-ups, o2 sensors, map sensor, idle air control, catylitic converter, injectors, ecu. ect.). The strange thing over the past couple of years is when the emissions guy here at work has looked over my failed emissions sheets and he has repeatedly said that it appears that the car is going back and forth from lean to rich or something. Now that I’ve replaced it I have a perfect idle and the cars feels like it accelerates much more smoothly.

The question is…Is it likely that the TPS was bad all along but not bad enough to throw the CEL? If that was the case, is ity possible that the signal it was sending to my ecu all along was causing my ecu to manage fuel improperly and cause my emissions issues?

Very possible. The only way to know for sure is with a scope or extremely fast multimeter. The ECUs aren’t exactly super sensitive on our cars, and TPS + MAP are the main sensors the ECU relies on to figure out what’s going on.

What kind of numbers was it putting out on HC, CO, and NOx?

I wish I could remember the numbers it put out last year. I had it passed the wrong way, if you know what I mean, last year. I’m going to run it today and hope it passes this time :cross:

The answer is, NO, I am continuing to have emissions woes. We ran it in test mode at 15mph and 25mph and it’s way high on NO and HC. One of the guys here in the shop thinks that because it’s run rich as much as it has I may have a ton of carbon buildup on the pistons and plugs (causing a misfire) and possibly may have fouled out the cat I put on last year in the process. He’s telling me to run some more top engine cleaner through it and then run about a gallon of water through it to clean up all the carbon buildup. I’m going to give it a shot here at the shop in a few minutes. Anyone have any other ideas? I really want to fix this problem. I’m tired of putting it off by paying off an emissions guy and having to go through the hassle of finding a new guy willing to do it every year. I’d really like to have this thing running right and I’m just completely out of ideas of my own at this point.