Cylinder 7 misfire...I think it's bad...

[Physh1]

Ok, popped a SES light last week. Happened randomly on the way home. 225k on motor.

Cylinder 7 misfire. Plug is clean but changed anyway. Coil was swapped with another cylinder...no change in miss. Changed wires...no change. I also put new injectors in all 8 cylinders. My mech friend checked injector pulse & it was good. No oil consumption, no bad mileage.

Compression tested 3 times...varied from 125 to 155. From what I understand 120 is low, 100 is what GM says is dead minimum.

I think I have collapsed lifters. While doing all this testing the top end in the #7 area started ticking...kinda verifying my worst thought.

Any suggestions?

I'm hunting for a new motor...but just wondering if I'm missing something.

Cameron

 

[redemn93]

sounds like you covered it all. lifters going bad arent exactly a phenomenon with these motors. do you have another vehicle to drive? why not pull the heads if so to see if its fixable. freshen up the top end, get a good valve job, make sure their flat and throw them back on. worst case youll know if you need a new motor when the head comes off.

 

[Chiggy]

Could also be a bent pushrod. Broken rocker. Broken valve spring. Pull the valve cover and see what you've got.

 

[SLCHOE]

You could try an engine flush. It's cheap and worth a shot.

 

[southboundchicken]

Had a similar problem and turned out to be a loose spark plug cap ( the threaded little cap that screws on top of the plug) if memory serves me correct i think these were some bosch plugs i installed so i replaced all the plugs with ac delco and was running like a champ after that