Ok I'll start from the beginning...About a year ago I noticed a stumble from my engine that felt like a misfire, so I started trying to fix the "misfire". I replaced the plugs, wires, distributor cap, made sure the injectors worked, checked compression, checked for vacuum leaks, ect... Nothing seemed to work. Now I wasn't sure then nor now that it was a misfire but that is what it feels like.
The main diagnosis problem that I'm having is that the "misfire" is not consistent. The stumble pattern is more like every 2 sec, 20 sec, 5 sec, 8sec, 3 min, 30 sec, 4 sec, 2 sec, on and on and on like that. Very sporadic and annoying.

Now here is the interesting part...I discovered a small leak fuel leak right before the rail (just an o-ring crack). Here I am thinking I found the problem. So I went down there and swapped the o-ring, put a everything back together and TADA... no more problem. I couldn't help but think how a small leak could cause a stumble like that, but whatever. So I drive for about two weeks and it starts doing it again. Slow at first then more and more. So I throw my hands in the air and just keep driving. But wait...it gets weirder.

A few months later my truck dies when the stumbling was worse than ever. I think to myself finally something broke, now I can fix exactly what wrong. I get it home to find that the distributor has locked up, totally seized. I thought that a bit strange but I replaced it and the engine fired right up, actually running better than ever. Again couldn't help but think that I finally fixed the problem. I drove around for a few weeks with more power, better idle, everything was great. But then a few days ago I noticed the "misfire" AGAIN! Slow at first but its getting worse.

The only thing I can think is that taking it apart somehow temporarily fixes it. My official diagnosis...My engine just likes to be worked on. It brakes so I'll give it more attention.

 

could be that there is damage to the distributor drive gear.

 

I'm with you; I think the engines need attention in order to run right. I stroke mine ever-so-softly every morning before I start it....

 

That just sounded really bad, TN....lol

 

When you know it is mis-firing run the engine in the dark and look for arcing around the coil, distributor, wires ect. Also check that there are a bunch of red wires that get grounded to the first section intake manifold bolts. Maybe take them off and sand them down a bit. They are your grounding for the injectors.

 

I'll do that as soon as it gets dark.

Another bit of confusion is that the stumbling is much worse if the rpm's for that gear are low, like taking off from a light or turning a corner in second gear.

 

Never had a chance to check for the arc last night cause of the rain. But I'll due it tonight. It makes sense that it might just be grounding out while the truck bumps around, and the work I do just moves it furthur from the grounding spot.

I love it when I'm this close

 

nah these trucks are 20+ yrs old. they need some lovin to

 

Just incase anyone was interested, the injector was grounding out on the intake!!. Two dollars to buy some electrical tape and there goes a yearlong battle with a mysterious misfire.

TADAHH