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Mike S.
Mike S., ASE Certified Technician
Category: GMC
Satisfied Customers: 7568
Experience:  GMC N.A.I.S.E. Certified Auto-Mechanic
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GMC: Have 1998 GMC truck c 1500 ...Getting 301 code Misfire

Customer Question

Have 1998 GMC truck c 1500 ...Getting 301 code Misfire # ***** after replacing Intake gasket. Have replaced wire, plugs, distributor cap and rotor. Did a compression test on #1 and its in line with other cylds. Also replaced cam and crank sensors. Gap on plugs at recommmended amount..I think was .06. Have not had cam and crank Synchronized. The misfire is more apparent when the engine is at full operating temp.
What else can I do? Pleas help
Submitted: 2 years ago.
Category: GMC
Expert:  Mike S. replied 2 years ago.

Did you ever complete the test or whatever on the #1 fuel injector or poppet?

There is one more thing that is most of the time overlooked and that is a wiped or flat cam lobe on that cylinder.

I recently bought a chevy small block cheap that had a wiped cam lobe on the intake side of #7. The previous owner must have tried everything to get rid of a misfire, spark plug, wire, etc but come to find out I bet he never knew if was a wiped cam lobe.

Customer: replied 2 years ago.

Yes, I installed a new fuel injector. How can I tell if I have a wiped cam lobe?

Expert:  Mike S. replied 2 years ago.

Measure the cam lobe lifts on both and compare them to the specs or just compare them to the cylinder next to it. You may be able to tell though by just watching how much each rocker arm rises on the side where the pushrod is and compare it to the cylinders on that bank. If it's too fast to see when the engine is idling then remove the fuel pump fuse or relay, so the engine won't start and just look at the lifts while cranking the engine over with the starter.

In order to measure correctly though you would need to use a dial indicator.

Customer: replied 2 years ago.

Will try and get back with you...I will also check the lash and look for broken spring

Expert:  Mike S. replied 2 years ago.
Ok, and don't forget a possible bent pushrod.