PO300 Code 1999 Tahoe Misfireing

[my72corvette]

Anyone having problems with a 99 tahoe misfireing? OK,, I am frustrated,,, I have replace the Spider fuel injector, Sparks plugs, Spark plug wires, Dist cap and rotor, Oxyen Sensor, the last was a Carnkshaft sensor... and it's still miss fireing... still get a PO 300... I have a 1999 Tahoe 350. When I took out the crankshaft sensor it was completely broken off. we thought that was going to be the problem but it wasn't.
ANY Help would be GREATLY appreciated.
THANKS

 

[BOSS]

I would run a couple cans of seafoam in the gas tank and through the intake before doing anything else.

To run seafoam through the intake, the best place is the middle of the intake which is usually through the pcv line that comes from the top of the valve cover. You can also use the brake booster line. You can search my threads as I had the same issue you do and Sf'd it away.

B

 

[steamroller]

Since you covered all the common problems, worn distributor gear

 

[JennaBear]

Clean your MAF.

 

[wicked2000]

You might have to change your O2 sensors. I had a bad injector changed it out and since it was leaking messed up my O2 sensors. I had just changed then out thinking my problem was that at first. I kept driving like that for a while but ended up taking it to mechanic thats when he told which injector was bad. I changed it out myself and when I fire it up it was better but light came back on. Took it back to mechanic and then it was O2 sensors. Cahnged them out problem was fixed. At the beginning i was getting like 4 codes.

 

[destroyer1362]

My misfire code was from a failing fuel pump. After replacing it twice within 2 weeks finally switched brands and the misfire was gone. So I'd check fuel pressure as well.