I have a 1989 B250 Van with 318 motor, no AC. On recent trips it has suddenly started running very rough, then it clears itself. On the most recent trip it ran fine forn1.5 hours, bobbled a few times, then ran fine again until the 3 hour mark. Then it really ran rough for a while. It feels like a misfire or lack of fuel. But then if clears and runs fine. I have recently replaced the spark plugs, coil, spark plug wires. Hall Effect Sensor replaced a couple of years go. Check Engine codes are 12 (disconnected the battery a few weeks ago), 26 and 33. Anyone got any suggestions?

 

Maybe pop for a new brass cap and rotor. Does it happen when you let off the fuel or under load? I've only had it stall out when coming off the throttle and that was solved by doing a tune-up as you've mostly done.

 

I received a message from Neil but figured I'd respond here since this is a common issue with no less than 3 people asking about it today. He indicated it was an off-throttle issue.

I think you just need a tune-up. Perhaps some of the parts you put in previously were not up to the job. There is also a TSB on how to route the spark plug wiring on the Magnums which you may want to follow. Do the spark plugs you bought match the sticker on the hood? The Hayne's manual shows the wrong ones. Change your fuel filter if you haven't done so. Some other things you can do is check your computer for codes and check your catalytic converter for plugging. The stumbling is a very common problem that people have.