1999 Tahoe 5.7L random misfire

[DR CHOP]

Check your cap and rotor and do a Midnight spark check on the wires. I still bettin on the injectors, just check everything else first.

 

[GMstrong]

if the dis cap is in good shape and the gear is not wore down then I would replace the injectors.

 

[Oleg]

Hey guys still trying to fix the issue. I just replaced the injectors to the mpfi upgrade and still same cylinder 2 and 8 misfire. If the distributor is bad would it cause all the cylinders to misfire or just a couple? The cap and rotor seem fine. They were corroded a little but i cleaned them up and there was not much difference.

I swapped the plugs and wires around to rule them out but the misfire stays at cylinder 2 and 8.

Any other ideas?

 

[scoob8000]

If the dizzy itself were bad it'd affect all cylinders. Now the cap however could be crossfiring between terminals however. 2 & 8 are close enough internally in the cap too.

I just chased a similar problem on my 98' throwing 100's of dollars in parts at it because my compression tester had a leaky hose and gave me bad readings. My problem ended up being a sticking exhaust valve.

First I would though check for vacuum leaks that could cause a lean condition. Externally with engine cool and running spray carb cleaner around the intake manifold and any vacuum line fittings.

If that doesnt show anything, pull the PCV out of the valve cover and plug the grommit, and the valve opening. Also plug the breather opening on the other valve cover. (I used the finger of a nitrile glove over the pcv and breather tube and just put them back in. Then with engine running, pull the dipstick and feel/check for vacuum there.

If all that turns up no leaks, I'd do a compression test next.