I just bought a 89 Iroc 1LE and its already having problems but im used to my 72 and i dont know fuel injection very well. Out of no where the car wouldnt start and im showing nothing on my engine codes, just the 12. its got brand new injectors new fuel pump so those are ruled out. The car was cranking but wouldnt turn over unless i gave it gas and countinued to hold the throttle open. so from here i turned the stop pin all the way up and it will hold a very low idle and is running extremly rich and will stall out as soon as it goes into gear due to the idle. the answer im getting from asking around is that its my throttle position sensor. i dont have a lot of money and i find the best way to learn is to do it yourself but i just want to make sure that this is most likely the problem before i go buy the part. any imput?

 

The not knowing can be a pain! Could be the TPS as you mentioned or perhaps the IAC or the fuel pump relay.... Nothing worse than spending 20 - 50 bucks on A sensor, that doesn't solve the problem!

 

The tps is very simple to check, back probe the electrical connector with a digital voltmeter, negative probe in the center positive probe in the bottem. Turn the key on but do not start the car,read the voltage. I think fuel injected motors should be about .51 volts ( i may be wrong on this as my car is carbed and get set at .48 volts. ). I believe there are quite a few posts on this subject in the carb section and probably in the fuel injected sections. When reading the voltage slowly move the throttle from idle to wot, there should be a smooth increase then decrease of voltage as the throttle is operated. If the reading is eradic tps probably need replaced. If voltage reading is not the correct voltage, loosen mounting screws and rotate untillcorrect voltage is achieved. Tighten screws and recheck voltage to make sure it didnt move while tightening screws. If it needs replaced they are pretty cheep at most auto parts stores, i think about twenty five bucks. Hope this helps and good luck.