2000 Chevy Silverado with 5.3 V8. I just replaced my MS98016T Intake Manifold Gasket, SK2451107 Mass Air Flow Sensor, 5S2172 Knock / Detonation Sensor (both) and 1P2069 Knock / Detonation Sensor Connector because of the common systems associated with a leaking manifold gasket. While in there I figured I might as well replace the Knock sensors considering the age of the truck. I didn't want to have to pull the manifold again in 6 months to replace those sensors. I followed all of the proper procedures for re-installing the manifold (torque procedures)

After installing the parts the original symptoms are gone and I am now getting a misfire with a P0300 code. It has to be related to what I just did but what could I have done to cause this.

At first I had a P0300, P0171 and P0174 but I did not know if the codes where left over from my previous issue. I cleared the codes and after lettting it run for about 5 minutes or less I got the Service Engine light and the P0300 code had returned. It was the only code.

 

Go back and recheck all of the electrical connections including those to the ignition coils and fuel injectors and make sure they are properly seated. While you are at it, make sure the spark plug wires are also properly seated.

If you still have a P0300 after that, then I suggest using a code reader and look at the misfire counts to see which cylinder is misfiring the most.

 

I thought I had checked all the connections but I double checked again and one of the fuel injector connections was not seated all the way. Problem solved. Thanks for replying.

 

Glad to hear you found the problem! Happy to have been of some assistance!

 

I thought I had the problem solved. The original problem was solved by the new parts. I then had the P0300 that was the result of a loose connector and or a vacuum line I missed and left off. Once I reconnected the vacuum line I thought my troubles were over. It runs great sitting there idling. At least until it starts getting to operating temperature. Once the engine warms up it seems to have a slight miss that appears to be a fuel issue just from the feel of it. It gets worse if I rev the engine or try to drive. It progresses to the point that if I try to accelerate it spits and sputters and sometimes catches and accelerates or it dies. It then becomes difficult to get started an won't hardly run. Once it cools down it runs great. At idle it starts out between 500-600 rpms but as the problem develops it wants to idle down slower and chokes out. Oh yea. New engine code. P0308. this code appears to be a catch all code not associated with any specific part or sensor. It only indicates a random fuel issue/miss-fire.

 

P0308 indicates a cylinder 8 misfire. Check the spark plug to see if it is wet - if it is, then it's not firing or too much fuel is getting into the cylinder via the injector. Try swapping the ignition coil with cylinder 6's - if the code changes to P0306, then the coil is bad. Also check the spark plug wire it might not be properly seated.

Several easy things to check/rule out before the need to delve deeper into the world of diagnostics.