Hi, this is my first post, but I have been registered here and reading for a few weeks.

My father has a 1994 Ford Ranger 4.0L(X) with about 140k. Performance was beginning to drop so we replaced the wires a few months ago with Autolite wires and single-platinum plugs. It smoothed out and passed the emission sniffer test with flying colors. Everything seemed to be OK, other than just age.

My father has been letting me use his truck while I'm repairing mine, and he failed to tell me its been having problems until after I picked it up. So Im stuck with fixing it now .

The check engine light comes on while driving, and loses power (Im guessing this is the computer switching between static and dynamic controls) It usually goes off within a few minutes. It seems to happen more at low speeds as opposed to being on the highway.

After going through the pretest checklist, I pulled the codes, and I got 111, and 157. MAF voltage too low during KOEO. KOER gives code 998 and 157. It wont run the test until I fix the MAF.

I did some searching here, and read about cleaning the MAF. I disconnected the battery, cleaned the MAF (very dirty) and the MAF housing, fixed a loose screw on the air box, and reinstalled. I started it back up, and still running a bit rough, and code 157 still there. I cleared the codes with the scanner, and still it persists.

The filaments of the MAF wer dirty, and I cleaned them with some CRC throttle body cleaner, and let them air dry. They were intact, and none appeared to be broken.

I read that some other sensors could trigger similar codes, is there a flowchart to follow? Should I check anything else?

Should I spent the $200 on a new MAF? Should I go with a parts store brand for about half the cost?

 

You need to test the output of the MAF sensor. I have a VERY HANDY little gadget for doing this. It's an Actron CP-9087 sensor tester. Cost me 10 bucks at the actron.com "garage sale" a few years ago.

Call around to some auto parts stores & see if they have one. Probably cost around 30 bucks.

Just remove the connector from the sensor, hook up the CP-9087, slowly increase the RPM's & watch the results on the tester. If the MAF is OK voltage will gradually go up as you increase engine speed.

Edit
The online price is ridiculous, but heres an interesting link www.actron.com/product_detail.php?pid=16163

 

My 94 was having the same problem, cleaned the MAF helped but was still pulling a code a week later. Cleaned again same thing. Ended up getting a new one from NAPA, it was under 80 or 90 if I recall. Replaced it and no more problems, that was over a year ago.

 

This is kind of off the beaten path from what you're writing about here, but it's something to check anyway. I too have a 94 4.0L and I took the entire intake flex tube off when I cleaned my air filter and noticed that the part of it that sat over the belt had rotted and chunked a hole about 2" dia. It was drawing air through this opening rather than through the air filter and I assume it sucked in the vinyl/plastic chunks from the flex tube into the intake.

Not good!

 

That's nasty. We think dust getting through the filter into the engine is bad, imagine what went in your engine when that hole was there.

I also have a '94 4.0L, thankfully no holes! Though I did go check after you mentioned it! lol, the guy who owned it before me put some kinda padding below the tube, maybe for that reason?

 

Some additional thoughts.

You need to find out WHY the MAF was so dirty.

It's supposed to see only filtered air, SO, if it was plenty dirty, I'd suspect a inlet air tube or air box leak, somewhere between the air box/air filter interface & the MAF.

I've read recently of mis fitting Purolater Air Filters in Rangers, so if your using that brand, carefully check it's fit in the air box & make sure the air box is buttoned up properly.

I've hard of folks having to clean the MAF as many as three times, to get good results.

I'd remove it to clean it, so you can get to it from all sides & not be putting the over spray & anyting it removes, into the air tube.

If the MAF was really dirty, then maybe the throttle body also needs to be removed & cleaned out too.

 

Im sure the problem it got so dirty was because one of the screw in the airbox was not seated properly. When [my dad] put the air filter in (Fram) he must have pushed the threads out of the airbox, and just left it like that. So it wasnt sealing properly around the filter.

Im guessing there was enough crud buildup that it overheated the sensor.

And yes, I took the sensor off the aluminum housing to clean it. I cleaned the air passage too.

And there are no holes in the air intake duct.

Thanks for the replys guys. I think Im gonna try a MAF from Advance Auto. GP Sorenson sp? Anybody have anything negative about that brand?

 

The sensor is very sensitive, it would have easily noticed it being dirty and given a false reading. I suggest the OEM MAF, but an aftermarket will be ok. Just make sure the wiring and most importantly the size is correct.
If he installed anything other than a Motorcraft filter, the MAF tends to get dirty quicker. They always end up dirty eventually, even with stock filters.

Just as a warning, Fram filters are known for letting small peices loose into the air duct/engine. Just a word of warning.