i have a 98 tahoe was driving down road then engine just started misfiring badly set a p0300 code it has a dead miss at idle now and runs on about 6 cylinders. when i step on it at full throttle it is poping back through the intake . when i barley touch gas it seems to smooth out but the more throttle i give it the worse it gets i had a tune up on it about 5 thousand miles ago cap , rotor , plugs , fuel filter and new air cleaner engine has been running great no problems at all . thanks for you replies
steve

 

had same problem with a 2001 chevy tahoe p0300
turned out to be intake manifold gasket
what happens after time the rubber on the gasket flattens and causes air to seep threw the intake causing a misfire felpro gaskets are the best the job takes about 45 min

 

would that cause a tapping noise in the engine? you hear it when driving and idling

 

to keep everyone happy, start a new thread with your question. you'll get better exposure, faster responses. and, welcome to our forums!

 

that sounds like your lifters, do you have afm on your truck? ive read a lot about the afm lifters are known to fail

 

This can be caused by all kinds of things. Air leaks, bad O@ sensor(s), plugs or wires, etc, etc.. I get that code while pulling my camper, not using overdrive and coasting downhill on an interstate at 65 miles per hour. It never does it any other time. It never runs bad. I would just start eliminating. If you think it's an intake you can test for that.