84 GMC

My truck is sick. 5.0 liter V-8. When it runs, rpm is too fast and it won't idle. When I go to shut it off it diesels real bad and doesn't easily turn off even if I leave it in gear. (Automatic trans) Tried
moving the distributor over one tooth. Worked great for 10 minutes. Somebody told me it's the oxygen sensor. Could that be it? Somebody please help. thank you.
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using a carburetor!) If so, remove air cleaner and stick a hole in the center of a pc of notebook paper. Slide the paper down onto "carb"(throttle body) allowing air cleaner holddown stem(bolt) to come thru the hole in the paper. As the paper begins to reduce air flow thru its top, it pulls more gasoline instead & makes it run richer; if it has a bad throttle body base gasket the engine will level out & increase speed. An easier way might be to spray WD-40 around the t-body base as it idles. If it picks up speed, same conclusion. However, often it's difficult for me to make a leak respond to WD-40. Before I knew BETTER, I'd spray a FINE mist of gasoline around that gasket with a spray bottle--if it was leaking air, the engine responded immediately, levelled out & increased speed. Finding a gasket leaking air will cause your symptoms. If so, replace it & enjoy its now slower, smoother idle. HTH & good luck. Fix it, Dianne, & show Ed just what a genius of a gal he's got! s
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