Question about 1995 GMC Sierra
I would try removing and plugging the vacuum line that goes to the EGR valve. If this solves your problem, you may have an EGR valve that was calibrated for a different vehicle and is adding too much exhaust during cruise. This problem can also be caused by a MAF sensor that is not "seeing" all the air that is entering the engine and causing it to run lean at cruise. Tough to say which one. If it were me, I'd try and find a loaner MAF sensor to try...maybe an auto wrecker? Either way, make sure your ignition timing is correct and the plugs are gapped properly. Low timing and a worn timing chain can also cause this problem. I suspect that this truck has high miles?
Posted on Mar 28, 2011
Have you run a test on the ECM (Electronic Control Module) to see if any electronic engine control fault codes are present for the engine or emission control system? This sounds very much like an EGR (Exhaust Gas Recirculation) valve problem or a TPS (Throttle Position Sensor) problem. Do the test first and see what shows up. You can do the test by watching the Check Engine light blink during the test. Go to the link below for instructions on how to run the test.
Posted on Mar 29, 2011
This is tuff, my first thought is the engine is missing, but you have replaced almost everything, but i do have a couple of ideas, the 305 had allot of problems with camshafts the lobes get worn down and do not allow enough lift for the valves, witch can cause a miss fire, when you gouge the throttle it seems to go away just because all the other cylinders pick up there output, about the only way to check this is with a compression test or remove the intake and look at the lifters to see if they are cupped out.
the 2nd thing is to check the coil output, it could be the ignition coil is getting weak, you can check the output with a spark tester, if you don't have one you can make one with an old spark plug, just take an old plug and brake the ground leg off of it then install it in a spark plug wire and hold the threaded part against a good ground and crank the engine the spark should jump from the center of the plug to the out side case and should be very bright if not replace the coil.
also the 305 V8 had allot of problems with the distributor shaft, it was even recalled many times for this problem, the magnets in the shaft that send a signal to the pick assembly in the distributor get cracks in them that cause all manner of running problems.
out of the 3 this was one we have seen the most, it is so common that most parts stores keep the distributor in stock.
i hope this helps, please keep me informed, and let me know if there is any thing else i can do foe you.
Posted on Mar 21, 2011
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Posted on Jan 02, 2017
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Jun 24, 2017 | 1995 GMC Sierra
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