Question about 1991 GMC Sierra
Truck idles as long as the map censor is unplugged
Have you plugged in a new map sensor and this happens, or just the original one? Could just be a bad sensor. Also you could have broken /exposed wires that are shorting out.
Posted on May 11, 2014
Testimonial: "Ty. I have tried 3 different MAP sensors. Small town ordered new one. No mechanics here either. I am a carpenter so this mechanic talk is as hard as fixing it lol wiring looks fine."
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Posted on Jan 02, 2017
test fuel pressure by renting a fuel pressure test kit from schucks or auto zone then turn key on then off if it hits 50 psi it's ok if it drops below 20 psi in one minuter then fuel pump is bad. if it has throttle body injection then replace the injector or pull it apart to see if it is plugged.check oil pressuer switch behind the distributor to see if it is bad it will cause it not to run if defective.
Posted on Jul 18, 2009
SOURCE: fails idle emissions test hc
****** ignition timing....this will lower HC but raise other values during test.
Do you have room to increase other values?
After test return timing to the most advanced position without spark knock under load for best MPG.
Posted on Aug 11, 2009
the throttle body is dirty, this will cause low charging system voltage and intermittant stalling. Push open the trottle plate and hose it out with throttle body cleaner. A tooth brush will help
Posted on Oct 19, 2009
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