My car has an intermittent problem. 99% of the time it is fine. But, occasionally, when the engine is warm and I go to restart it, it starts up and then dies right out. If I step on the accererator a little bit, I can keep the engine running fine, as soon as I take my foot off, it dies. Sometimes it will idle real slow and the oil pressure light comes on. But usually it just dies. I have never had a problem starting cold.
Today it happened and I had my new scan tool with me, so I had a great opportunity to play with it. The only weird thing was the fuel trim. Usually the short term fuel trim is between -5 and +5. Today as the engine was just about to die, the fuel trim was going over 20%. I don’t know if that’s significant, but it seemed really high.
I thought maybe I could somehow force it into open loop to get it running. I unplugged the DPFE, but nothing changed. The scanner still showed closed loop mode. So then I unplugged the throttle position sensor. This time, the scanner still showed closed loop, but I was able to get the engine to idle. And it wasn’t just a little better. It was like it was totally fixed.
What do you make of this?
What year is your car? If it is a year prior to the switch to electronic throttle control, then the idle air bypass valve (aka IAC) sticking is a good bet from your symptoms.
That had crossed my mind. Now that you mention it, the TPS is right next to the IAC. So I very easily could have jiggled the valve loose while I was yanking on the electrical connector. Next time it happens, the first thing I will try is tapping on the IAC. Thanks!