random misfire after head gasket (1 Viewer)

[cvenom96]

Ok I've searched but didn't find anything conclusive. No check engine light. It fired up pretty quick after the head gasket was replaced and ran smoothly for about 30 seconds before a random misfire started. It will go from smooth for about 5 or 6 seconds then a miss, then smooth again and another. It's not consistent like a dead cylinder. It seems to be a little worse at idle which it has a tough time doing. It idles low anyway after the battery has been disconnected for some time until it has a chance to relearn so that doesn't surprise me too much. If it dies, it will crank up and run smooth again for about 5 or 10 seconds then start with misfire again. My guess is bad cap/rotor or a vacuum leak somewhere under the intake. Thoughts?

 

[BILT4ME]

Ok I've searched but didn't find anything conclusive. No check engine light. It fired up pretty quick after the head gasket was replaced and ran smoothly for about 30 seconds before a random misfire started. It will go from smooth for about 5 or 6 seconds then a miss, then smooth again and another. It's not consistent like a dead cylinder. It seems to be a little worse at idle which it has a tough time doing. It idles low anyway after the battery has been disconnected for some time until it has a chance to relearn so that doesn't surprise me too much. If it dies, it will crank up and run smooth again for about 5 or 10 seconds then start with misfire again. My guess is bad cap/rotor or a vacuum leak somewhere under the intake. Thoughts?

I would look at injector plugs and spark plug wiring first.

 

[2fpower]

Did you set timing per FSM?

 

[cvenom96]

Did you set timing per FSM?

Winner winner chicken dinner. I thought it was pretty close based on the positioning marks I made prior to removing the distributor but, was slightly off. Running smoothly now.

 

[cvenom96]

Overall quite a bit of labor but not as terrible as I expected. Found and replaced a few more hoses that were old. My injectors came back from cleaning and the most improvement any one of them got was about 8% increase. Not bad for 316k miles I suppose.

 

[OffRoadScott]

Could be a couple of things. The harness near the EGR has finally started to short out and could be causing your issues or your injectors could be dirty too. I am in the process of chasing down the same gremlins and am swapping out the harness and getting the injectors cleaned while I am at it.

After you got the head cleaned and installed the poor injector performance could be more noticeable now than before.

Also, I would recommend replacing the vacuum hoses under the upper intake as well.