‘90 4.0 CHECK ENGINE Light turns on and off while driving

[RangerReviver1990]

My check engine bulb was taken out before I bought the truck. And I just started driving it last summer to and from school/work. Yesterday, i added a new bulb and put everything back together and i started it and everything seemed normal and then the CEL came on about 3 seconds after starting. My truck runs good so I didn’t think nothing of it and shut the truck off. Later that day i was driving to the store and kept turning on and off at random intervals. And this morning, it would either stay on for 15-20 seconds and then shut off or just blink once, but once i got up to highway speeds, it didn’t turn on once. What does this mean?

 

[Shran]

Did you check to see if any codes were present in the computer and if so, what were they? The CEL will only come on if the ECM detects an issue or if there is a wiring fault with the light itself...unlikely.

 

[RangerReviver1990]

Sorry for the late reply. I did the thing where you stick a jumper wire/paper clip into the computer connector and watched the engine light blink and I got 22 and 51, which is my MAF sensor and my BARO sensor that were going bad. I replaced those yesterday and my light still comes on at idle and turns off while accelerating and turn off completely while on the highway.

 

[SenorNoob]

Mine does very similar except I have a code for lean or rich one. Can't remember which. Pretty sure I cracked the O2 senor changing the transmission. I've been unable to remove it since. Planning to do that when I replace the engine. Gotta cut the y-pipe loose then anyway...

 

[89RanBrII]

Sorry for the late reply. I did the thing where you stick a jumper wire/paper clip into the computer connector and watched the engine light blink and I got 22 and 51, which is my MAF sensor and my BARO sensor that were going bad. I replaced those yesterday and my light still comes on at idle and turns off while accelerating and turn off completely while on the highway.

What is your air filter like?

 

[RangerReviver1990]

What is your air filter like?

It's extremely dirty on the bottom half, I just replaced it couple minutes ago and I even unplugged the battery to try to reset the computer and it's still coming on

 

[sd359]

I had a similar problem several years back. Check engine light coming on at random. Got a low voltage MAF sensor code. After many hours of checking I took it to my buddy who runs a garage. It took them over 10 hours to find the problem. There is a wiring harness that goes in behind the battery. It can rub on the battery box edge and it will start cutting wires and they will ground out causing the codes. I have a 94 4.0 4x4 ext cab. Had a friend a couple weeks ago his truck would not start and he check behind the battery and found same problem on a 88 w/ 2.9. Just an idea of something to check.

 

[RangerReviver1990]

I had a similar problem several years back. Check engine light coming on at random. Got a low voltage MAF sensor code. After many hours of checking I took it to my buddy who runs a garage. It took them over 10 hours to find the problem. There is a wiring harness that goes in behind the battery. It can rub on the battery box edge and it will start cutting wires and they will ground out causing the codes. I have a 94 4.0 4x4 ext cab. Had a friend a couple weeks ago his truck would not start and he check behind the battery and found same problem on a 88 w/ 2.9. Just an idea of something to check.

I might have to check, I never would’ve thought of that. Thanks