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GMC Sierra problems

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New User

Oct 19, 2010, 8:39 PM

Post #1 of 3 (3013 views)
GMC Sierra problems Sign In

I have a 1991 GMC Sierra SLE its a k2500 with a 5.7 liter engine it has a/c and is a 4x4. it has 200,00 miles. As of now the truck starts up immediately upon turning the ignition. it idles really rough and spews out black smoke. if I pull the injector plug or the ecm fuse the truck runs perfectly until the fuel line empties. I just changed fuel pressure regulator the throttle position sensor, knock sensor, plugs, distributor cap and rotor and all plug wires. I'm lost. HELP..........................

Veteran / Moderator
Sidom profile image

Oct 19, 2010, 9:09 PM

Post #2 of 3 (3011 views)
Re: GMC Sierra problems Sign In

I think it would be good to start with some basics. Pull the codes and see if any codes are there, you may have to run it and check before shutting it all the way off. A fuel pressure reading would be good and also how long the pressure holds. It would be real helpful if you could look at the comp datastream and see what some reading are, the coolant temp in particular.........

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 20, 2010, 6:59 AM

Post #3 of 3 (3005 views)
Re: GMC Sierra problems Sign In

I'd do exactly what Sidom suggested and and just add that the CTS (coolant temp sensor) is suspect. Check the plug to it and if you replace that get one with a pig tail wire to solder in properly. It should have a yellow wire and another I forget right now near the thermostat like a spark plug they just screw in,


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