I have a 1989 2600i 4x4. I filled it up with gas and it has not ran good since. It was misfiring and backfiring so bad that it blew a whole in the muffler. I changed the fuel, fuel filter, plugs and plug wires and it ran good for a week. It then started missing again(not nearly as bad) and the oil light comes on at idle speed but goes out when you rev the engine. Checked everything I did before and timing which all seem ok. Checked voltage when running and it is over 14V. When idling if you slowly rev the engine it runs ok but starts missing after time. If you punch the gas real quick it misses and all most dies. Checked for vacuum leaks, could find none. I have a feeling it is something with the computer but am not positive and dont want to spend money needlessly if I dont need to. Any suggestions?
Thanks in advance Dave

 

Forgot to mention that I replaced the oil sensor with no help. It drive ok as long as you dont punch it. When you do it really starts missing bad.

 

sound like u may have got some bad gas or a dirty tank and plugged the pick-up screen on the fuel pump in the gas tank or the pump is starting to fail
try and have the fuel pressure checked

lack of fuel= lack of power

 

Hi dmalensek,

Have a 1990 B2600i 2wd, auto-trans. Mine was doing similar things and I chased the problem(s) for about 2 months. Replaced the fuel tank, fuel pump, fuel filter, coil, distributor, cap, rotor, plugs, plug wires, injectors and FINALLY replaced the circuitboard(cpu...computer...it's called various things) located just ahead of the passenger side door under the kick panel. EVERYTHING cleared up. Turns out the early B2600i circuitboards were manufactured by Mitsubishi(as were the engines)and had a capacitor that leaked and shorted out the board. Found this out on another website. It's simple to remove. Just pull the panel and it's right there. 4 screws. Carefully pry it off the posts and take it to your local parts store where they can check it. They're expensive. $350-700 for a rebuilt one, but way, way worth the money. If I'd STARTED there I would've saved myself about $1200 in parts/labor. Also, there's a modulater in the distributor which shorts out as it heats up when going bad...may want to check there, too. Good luck! I'll check back.