Random Cylinder Misfire

[98chevy2500SS]

A distributor drive gear? huh, I didn't replace that, I guess it is worth a shot. The only thing I replaced was the distributor cap.

I re-checked the fuel pressure after I changed the fuel filter, and it said 52 psi at idle and 60 psi at higher RPMs.

I guess I look into a drive gear.

Would it still be a good idea to replace that cylinder head? I got it off of my parts Suburban, had the Vortec 5700.

 

[silverado98]

CHANGE UR WIRES AGAIN THE SAME THING HAPPEN TO I REPLACED EVERYTHING SPIDER,FUEL PUMP,FILTER,PLUGS,CAP,ROTOR,EVEN IGNITON COIL AND NOTHING BUT THEN I SAID ONE DAY LET ME DO WIRES AND BOOM GOOD TO GO THE WIRE INSIDE AND BENT INSIDE DONT HOW BUT ONCE I CHANGED THEM IT WAS GOOD TO GO SO I SUGGEST TRY THAT

 

[98chevy2500SS]

I guess I could try that, maybe I will stop in to the auto shop and grab 8 new plug wires. If you are correct, that will lighten my day and I can finally drive my truck again! Haven't driven it in over a week because of this issue, I am so sad. Got a lot of stuff for it at the Swap Meet last weekend... sorry rambling on, but yeah I will change those and get back to you guys. I hope this is the fix.

 

[silverado98]

let me know how it turns out

 

[98chevy2500SS]

Well, we did the cylinder head fix and it fixed the problem! I am so happy that my truck is drive-able!

The passenger side cylinder head had a crack on cylinder 4 right next to the exhaust valve. Hope this helps anyone if they have this problem. It has had this crack since I owned, which was about 2 1/2 years ago.

 

[98chevy2500SS]

Shouldn't have spoken too soon. Just drove it today, still feels like it is sort of bucking when gassing it, like it is being held back of fuel or power. Could it be the fuel pump? Is it common for these to fail when the mileage is about 138k miles?

 

[Greg Mck]

I'm curious on this one too have a similar problem. P0300 always on replaced cap and rotor twice, replaced ign coil, module and replaced the distributor. Always comes back. The will start up and run good for a while then it will start back firing and missing. Then I would floor it and it would clear up and run right for a while then start misfiring again. I'm stumped.

 

[98chevy2500SS]

Well, here's the thing. Once I replaced the cylinder head, I was flipping through the scanner and it said Cylinder 8 misfire. Tried it the next day with the new head, "Service Engine Soon" light came on. "WTF now?!?" I thought. Well, come to find out, yesterday evening, the spark plug was fowled out. Replaced that, check engine light went off today as I driving it, runs smooth as silk. No bucking/chugging etc. anymore. Maybe you could try all new plugs @Greg Mck on your truck, it could possibly be a darn spark plug that's f'ing everything up. I too did the same things you did, and nothing worked, I would definitely change spark plugs and check for fowled out plugs. It's just amazing how such a small thing could cause such a HUGE problem.