Okay, I give up, I surrender to the curse of the Storm.
Problem car is a 91 Storm, 1.6L, Auto, Non-Turbo.
Developed a hesitation, a real nasty one. It runs great until it is fully warmed up then it starts. It is only off the line. Once it is turning it runs ok. If you pull away from a traffic signal it may or may not move. You have to tease the pedal to get it going if it acts up.
Thinking it was the emissions system, and I still do, I went after it. It had an intermittant O2 sensor code, replaced that and replaced the map. Tried some parts swapping from a 90 Storm, long story on that one. Still hesitated. Even tried a distributor swap from the second storm.
Got a bargain on an Actron Sensor Checker. Double checked the new O2 and MAP. Both Good. Everything else checking good except the IAC. IAC shouldn't cause a hesitation, I think. Besides, the checker says its ng but it seems to be working ok.
During all this I had it running fine for about two weeks. Thinking the problem was maybe a non-ecm connected component I suspected the EGR. In checking that out the valve itself seemed ok. The Backpressure transducer tested bad. Put the alternate one in from the other Storm. For two weeks the thing ran great. Now we're hesitating again but, on the other hand, the egr seems fine now.
I am going to take one more look at the emissions components next. I
better also check the wiring to the ecm from all sensors. It really seems to be emissions related. Again, it runs great before it is fully warmed up. Also, if I disconnect the MAP after it is warm it runs better, not great, but much better.
Have I missed something obvious in all this? Have I missed something not so obvious? Could it be the IAC after all? I am actually going to have to pay a pro to diagnose this thing if I can't get it to behave. That's terrible
