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Intermittent Start Stall/Crank No Start without throttle input
2001 Buick Lesabre Custom 3800 engine 358,887 miles
I have an intermittent start stall/ crank no start without throttle input. Solus ultra data shows desired idle speed all over the place 0 to 1600, the graph line actually looks like the upstream O2 sensor line. IAC counts all over the place from 0 to 255. I can control idle speed with scan tool and it stays within range stated in service manual. Checked IAC wires with incandescent test light and have activity on all wires. Cleaned throttle body (it needed it). No codes until the episode this morning; passed a vehicle on the way to work and engine speed stayed high with no throttle input. Pulled over shut it down and restarted, engine speed still high, tried one more time same result. Popped hood and verified throttle was shut, unplugged IAC, started engine and engine speed was high but drivable. Finished my day at work and wife brought me the solus, plugged in IAC and checked codes. Had P0122, P0507, P1122. Fired her up and ran fine, controlled idle fine with scan tool, drove home fine.
I hope I'm missing something simple but the data looks funny and it runs fine. I'm confused on whether it's the ECM or not.
So you've had an ongoing problem with the engine needing throttle? Then this morning the high rpm episode? Both could be caused by a sticking IAC. And if the throttle body was dirty chances are so is the IAC.
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