Hello everyone. I have a 2000 Bravada that has had a misfire on cylinder 6 for about two years since ive owned the vehicle. When I first started to fix the misfire I replaced everything that other people had mentioned;

spider assembly
new cap and rotor
new coil
crank sensor
cleaned egr
fuel filter
plugs and wires
etc..

Well my fuel pump died on me and with this being my busy time at work i decided to go to the stealership and have them do it. while it was ther i had them run a diagnostics on the misfire. They told me that cylinder 6 had low compression. they are assuming that it is not the rings since i dont burn any oil and they are positive it is not the head gasket.

So that leaves the valve i would imagine. I am confused though because about a year ago when i changed the spider the misfire went away for about a week but then returned. Just about two weeks ago i started the truck and viola! the misfire wasnt there and the check engine light went off. this lasted about a day then the misfire returned once more. What does this sound like to you guys? I at first was leaning towards maybe a burnt valve or cam lobe but if that was the case it wouldnt have gone away. Any ideas? Or thoughts?

Thanks. Sorry for the long post

 

Anyone have any ideas?

 

Weak valve spring? Worn lifter? Worn pushrod? Rocker out of adjustment or loose?

 

Have you noticed the coolant level dropping and can't find a leak? Have you pulled #6 spark plug and checked for coolant on the electrode? The intake runner for #6 is next to a coolant passage and the intake gaskets are known to fail on 4.3's Usually they leak externally or internally into the oil, but there's no reason it couldn't leak into the runner... just a thought.

 

Coolant level is good never has dropped down, not even a little. Plugs all look good and the dealer said the same that they were good looking. The thing that confuses me is the fact that it went away for those two times then came back. I havent had a chance to pull the valve cover yet so i will look at the rockers and see how everything looks. Any other ideas?

Thanks for the replies

 

Is the SES light on or does it flash when misfiring? Are there any DTC's either pending or set in memory?

 

Ses is on but never flashes, the only code its ever shown is p0306.

 

"Reading" #6 plug will tell the tale. Wet, dry, tan, black, white, carbon fouled, etc. If it's misfiring, it will not "look good". Can you post a close up, high resolution picture of the electrode? A couple of different angles would be good

 

Does the motor actually feel like it has a misfire???

 

It does feel like a misfire just sometimes it is worse and sometimes just barely there. Honestly the plugs look really normal, sorry about the looking good part lol I meant just for the coolant question looked good. But the plugs look normal, no excessive carbon, not wet, gapped properly, not white just as good looking as normal use plugs. Sorry no camera at the moment lol