'85 Ranger rough running/15mpg

[jpack]

My '85 Ranger (4cyl/EFI) has bouts of extremely rough running, as if only 2 or 3 cylinders are hitting. I can start out at normal acceleration and feel the "chugging" down the road. I may drive 50 yards or 5 miles with this happening, then the engine fires up, running like nothing ever happened. Even when running rough, I can accelerate and the chugging usually (not always) goes away, but will return when I level off on speed. I can accelerate to 55 mph, then ease off on the gas. Instead of staying at 55, it will sometimes slowly lose power, as if being fuel starved. Most of the time, though, once I get to speed, it runs smoothly; I can cruise the interstate at 65 with no problem.

The most frustrating thing is that this is not an every time thing. It may go a couple of days running fine, then act up periodically for a week. It may go through bouts several times in one day. When it is running rough, it literally feels like 2 of the cylinders are dead, but the eventually come back to life.

Mileage today was 14.5 mpg, combined town/highway.

Other than putting a bullet through the radiator, any ideas?

Thanks for any help.

[Mac626]

I'm having a similar problem on my 94. The codes indicated it might be related to my coil(s), and it definately seems to be electrical. I know that bad coils do cause intermittant problems.

I'm due for a tune up, so I'll be replacing plugs, wires and coils shortly to see if that solves the problem. It also indicated that my TPS (throttle position sensor) might be screwy, but it tests out fine.