Hi Everyone.

I just finished working on my Mothers 94 Explorer. It had a real bad problem with engine knocking/ detonation, on any type and kind of fuel, even super premium. The check engine light came on and stayed on frequently. I had Autozone do a free code scan, and the code came up with "rich limit reached, out of range" (OBD1 code # 86 I think).

I did a bunch of research and planned on replacing the knock sensor and EGR valve. I did a bit more final research, and came across the suggestion that the problem was a sooty/dirty MAF sensor. This is the site that I got the info & instructions from can be found at this web address:

http://www.glue.umd.edu/~singletn/web/pages/ping.html

I never thought that this would be the magic bullet that it turned out to be, but boy was I surprised.
The MAF sensor is right after the Airbox. It requires a special Torx type tool to get the 2 screws off. They have metal stud guards in the center to prevent the Torx being used, but you can hammer these down with a pin punch (carefully!).
Be careful of the MAF, clean the 2 diode type elements with Carb cleaner & reinstall. Reset the truck system computer by removing the Neg & Pos battery cables for about 10 mins.

You now have a truck & engine that goes from being ready to blow from detonation to running like brand new. A true magic bullet. I still may change the EGR valve, but the Knock sensor is going back.

 

Hey Violator,

Glad to hear you are winning the battle against those nasty pings! That link you posted is very informative, especially the pictures of the MAF sensor wires on the early 90's 4.0L.

The MAF on the 4.0L is very similar to the one Ford puts on the 3.0L. There is a thread in the 3.0L V6 Forum on cleaning the MAF which you also might find interesting:

MAF Cleaning

 

Thanks...I checked it out.
Take care!