Hello all,

I'm new to the forum but have been lurking for quite a while. Last week I started having an issue with my 94 4.0 ranger. As I was driving, the engine started running extremely poorly with a pretty hard misfire on at least on cylinder and the check engine light came on. I pulled to the side of the road and it shut off and wouldn't start for a while but would crank just fine. It seemed as if the truck had lost spark and would only attempt to run once it cooled off a bit so I replaced the ignition control module with a known good part with no change. I then checked the codes and got the two codes 117 and 122. 117 relates to low voltage on the ect sensor and I think 122 relates to the tps if I remember correctly. I know the ect was replaced a couple years ago by the previous owner and I'm almost sure it's not a motorcraft sensor (I know these older fords are extremely picky with aftermarket sensors). How much resistance should I expect to see when I ohm out the sensor? Also, I'll check for galvanic coolant in the morning as well. I was always told that I should see less than .5VDC. Any other suggestions? Maybe check relays?

Thanks in advance

 

Welcome to the forum

Seems like its time for the 1994 computer capacitors to fail
Just had to replace my 3 capacitors last June
And there have been a few more posts with the same problem, it causes odd engine issue, there is no set symptom

So I wouldn't waste time on other things until you have had a look at the computers circuit board

Pictures here: https://www.ranger-forums.com/4-0l-o...a-rich-164218/

The 3 capacitors should be replaced regardless once the computer is out, under $5 for parts
One of mine I thought was good was bad, lol
Then you are set for the next 25 years even if computer wasn't the issue

Sensors rarely fail, all my 1994 sensors and controls(IAC Valve) are original, if you test with OHM meter just see if there is a connection inside, if so then sensor is most likely OK
The simple act of unplugging a sensor and plugging it back in cleans the contacts that's usually why a new sensor can fix a problem, lol

O2 sensors DO run out of chemicals, so should be changed every 150k miles or 12 years
And ECT sensors can fail after 25+ years

 

Okay, thanks for your help. Are you referring to capacitors in the PCM?

 

Yes, that's the place, also general circuit board look see

Google: 1994 ford ranger computer removal

There is a video How-to, 1993/1994

I had to pull the large round firewall wiring harness off to get PCM wiring harness to move out of the way enough to access the PCM, just 1 bolt in the center, not hard to remove and easy to reinstall
PCM is another story, lol, but just a little more work getting to the lower nut

 

Yeah, it looks like pulling the inner fender to make it easier. Thanks for the help and I'll get back to you when I get results.

 

I used a long extension and wobble socket to get the lower nut off

 

Quick question, how firmly should I have to pull on the connector going into the pcm to remove it? I'm trying to be careful as its about -13F with wind chill and I am working outside (full-time college student).

 

After you take the center bolt out you need to wiggle it back and forth