This is going to be very long but I am at a loss for a solution to my problem. Any help/advice would be greatly appreciated.

The story.....

1991 Explorer Sport (2D, 2WD, 5 Speed) with 4.0 & 200k miles on it. Started running bad so I changed the plugs (fixed problem before and it had been around 60k since last change). Noticed when I changed the plugs that the wires were still stock and could use to be replaced. With new plugs it ran a little better but was getting bad gas mileage and running rough.

Decided to change the wires as it was running worse & worse and noticed that one of the coil pack connectors had coroded completely away. Replaced wires & coil pack and the truck ran great - for around 1 tank of gas.

Filed the tank up and instantly the truck ran bad - figured bad gas. Tried water remover but no improvement. Continued running worse until it would barely run at all. Started seeing black smoke (fuel) running from the exhaust of the truck. Started smelling "rotten eggs" so replaced the catalytic converter. Still runs bad.

At least two tanks of gas now and no improvement. Have replaced the oxygen sensor, fuel injectors, mass air meter, and TPS. Ran the system test on the EEC and the only fault code found was bad TPS (that is why it was replaced). The thing runs so bad now that it is not driveable.

Have also replaced the fuel filter - no improvement.

Checked static fuel pressure at 44lbs. At idle it is 36lbs.

Checked vacuum line from fuel pressure regulator for fuel but found none.

Have had to replace the plugs twice since just to keep it running.

Occasionally when driving it will suddenly run great for a few miles. Then, for no reason, it will run bad.

I have a friend with a 91 Navajo so I put his EEC in my Explorer and it made no improvement but also did not run any worse.

I am literaly getting around 5 mpg now. If it were an older car I would say it felt like the distributor was bad. Since this uses a crankshaft sensor I would think it would either work or not work. Don't know for sure though....

I don't know what else to check. I actually love the truck and really want to fix it. The sad part is I have as much in replacement parts as it is probably worth (have also just replaced the tires & clutch).

Thanks!

 

From your descriptions, Looks like your fuel pressures are on the high side of range. I would replace the fuel pressure regulator, clear the computer and start over.
Haynes manual lists pressures of 35-45PSI key on/engine off (or running with vacuum line to regulator disconnected)
and 30-35 PSI engine running (with vacuum line connected). A properly functioning regulator should be on the low/mid end of these values.
This item has appeared in many posts as a culprit for a host of problems from hard start to to excessive fuel use.
Dialtone

 

I have a 1997 4.0 L 4WD Explorer with a newly rebuilt engine. The Explorer is eating up fuel and has no power.

After doing all the stuff you did, discovered the problem was the Cam Position allignment sensor... This could be your problem.. The Cam sensor tells the fuel injectors when to fire. If the sensor is bad, your Truck will not run well at all.

Check this out...

Also. with 200K, your timing chain could be (is probably) stretched. This will put your car somewhat out of time and cause similar problems.

Hope this helps.