fasteddy
Web Wheeler
Reged: 01/30/01
Posts: 12704
Loc: Flat Creek, GA
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Re: 91 MM stumble
06/30/12 05:46 PM
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Pinch off the fuel return hose from the FPR and take it for a short drive and see if the stumble disappears. This will diagnose the FPR as bad or not.
Check the tps voltages, both at idle position and as you cycle the throttle, looking for dead spots and a smooth transition in voltage from about .5v up to where it maxes. Report wot voltage.
Really no way to check the maf except swap for known good one. IAT is in the MAF, iirc.
Also check ect sensor - should be a two blade fatter sensor on the water neck with blades in a tee shape. It's a thermistor, Check resistance engine cold and warmed up.
When it's stumbling, pull over and smell the exhaust. Does it smell gassy or acrid?
Check spark quality. Pull a plug wire and stick a phillips head screwdriver in the plug end of the wire, and have somebody crank it while holding the shaft of the driver about 1/4" away from and engine ground. Should see a blue white strong spark that jumps at least a quarter inch. Yellowish spark is weak - may be a failing coil.
Last check. In the dark, idle the truck up and down in rpms and look for spark leaks. Also look inside the distributor cap for carbon tracking and check the condition of the rotor and carbon button under the coil wire connector - seen broken buttons which will weaken the spark.
Just thought of one more. Check for a vac leak at the brake booster hose.
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"If you can't be a good influence, don't worry, you can still be a horrid example."
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