My engine was rebuilt about 2 years/20,000 miles ago. It ran perfectly until a few weeks ago. All of a sudden, it developed an intermittent dead miss that I corrected with new plug wires. After that, the miss was gone, but the truck was still a little sluggish.

About two weeks later, the truck idled and cruised smoothly but started to miss again. Instead of a dead miss though, this miss only occured under acceleration. In some cases, with larger amounts of throttle, it would backfire.

Last week, I replaced the plugs, cap, and rotor. All 8 plugs looked exactly the same with no evidence of any problems. I also gave it two bottles of fuel system treatment. These changes helped it idle and cruise better, but I'm still getting the same misses & backfires under acceleration that it had before last week's work. I don't think that it's a fuel system problem because if gas wasn't getting dumped into the cylinders, then there wouldn't be any be backfiring.

Since I have replaced all of the cheap & easy tune-up type components, the only thing I can think to do is check the codes. Before I do that though, does anyone have any ideas on what else to check?

 

Check your timing. Your distibutor might have rotated. Some of the other guys might have some additional ideas.

 

I was thinking of that, but would the timing only affect it during acceleration?

I'll check it anyway. 10 degrees BTDC right?

 

Sounds to me a little like cross firing . have you checked it at night ? if not check the plug wires in the dark for cross firing . ya 10 BTDC with the spout connector removed .

 

Have you checked for any codes yet?

 

Someone else said crossfiring, I'll check on that too.

Dumb question here - what's a sprout connector? I'm definintely not a mechanic, but I've messed around with cars for a long time and never heard that...

I haven't checked for codes yet, but I'm pretty sure I will have to. I'm just trying to go through all the possibilities before I go to the codes...

My hunch is that my timing isn't advancing like it should under acceleration. Since the advance is electronically controlled, I'm worried that my EEC computer is bad...

 

The spout connector is a little plug that you unplug to check timing. When the plug is pulled, the computer doesn't have control of the timing.