93 explorer Runs horrible...sometimes...

[R93ExplorerSport]

Got a 93 explorer sport with about 120,000 miles. Bout a month ago the problem started...but know its getting worse. The truck sometimes runs absolutely perfect, but sometimes runs like its down a cylinder. If i started the truck, and it starts up and runs good, it will continue to run good until i turn it off. If i start up the truck, and it runs likes its down a cylinder, its bad. It can last from 30 seconds to the time i turn truck off. Plugs and wires replaced. no smoke. oil is good, coolant looks to not be going anywhere. Help me out!! It just seems strange to me that it can either run perfect, or run like absolute crap.

Oh yea...CEL has came on once...and it came on while the truck was runnin good. Never came back on.

Thanks

 

[MrShorty]

1st thing I'd probably do would be to pull codes from the computer. See the stickies in the EEC-IV forum for instructions.

Just about other test is going to have to be performed when it is running bad. I'd probably look at a fuel pressure test, check for vacuum leaks, and check plugs and wires.

 

[Earl73]

One possibility...

...is that there is a large piece of debris in the fuel filter that blocks the passage of fuel at some times but not others. Fuel pressure could press it out of the way and keep it there when it is running well, and a bump in the road could move it when it goes from bad to good.
If you have never changed the fuel filter, I would recommend doing that just on maintenance principle, even if it doesn't fix the problem.

Another thing that I have had happen on one vehicle is a loose chunk of material in the cat converter that broke off the catalyst matrix. That vehicle did what yours is doing for a couple months, and then more pieces broke off and it wouldn't run more than 12 mph because the engine couldn't exhale.