1990 k1500

Asked by Brian Nov 07, 2017 at 08:35 PM about the 1991 Chevrolet C/K 1500 4WD

Question type: Maintenance & Repair

my 91 k1500 runs rough idles rough but when you
first start it its not as bad but after a minute or two
it cuts out every time you give it throttle and it
barely idles at all

1 Answer
145

John answered 7 years ago

sounds like fuel delivery issue or a vacuum leak. Could be clogged injectors, fuel filter of fuel lines. Could be the fuel pump is dying. On these trucks the fuel pump only works if oil pressure is present and seen by the ECU so a bad oil pressure sending unit could be the issue. Start with the Basics- Fuel/Air/Spark/Compression Fuel- is it getting adequate fuel? Measuring fuel pressure at the throttle body injectors will tell you. AIR: Is the MAF sensor telling the ecu bad info? Cleaning it with MAF cleaner may solve the problem. Also check for cracked or loose hoses and fitting between the air box and the throttle body that may be letting in unmetered air. Spark- Since it will start, you have spark. May cause this problem if weak but not likely culprit. Compression- If the truck has been burning oil for awhile you may have a worn out set of valves or rings causing massive misfire. Less likely Most likely a dirty MAF sensor or clogged fuel delivery (pump, filter or injectors)

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