I've got a 94 pickup that's throwing codes 24, 25, 31, and 41. It's got a misfire sometimes, which is pretty bad. I can drive the truck super easy and it runs fine, but a soon as I go to give it gas it starts missing. I don't know where to begin on this and I can't asked to just throw money at it until I get it figured out. Can anybody point me in the direction to start or how to go about troubleshooting this? Thanks, this forum seems to be chock full of people who knows these trucks well.

 

24 = Intake air temp sensor fault
25 = AFR Lean
31 = VAFM signal or vacuum switch fault
41 = TPS signal fault


24, 31 and 41 suggest an issue in the wiring between the firewall and around the intake manifold, possibly the ground in that section of the harness isn't connected. Also, maybe the little terminal in the harness connectors at the VAFM and TPS aren't seated properly.


These 3 faults could cause 25 to occur as they all will affect the air-fuel ratio.

 

I would check the connectors to the AFM and TPS first and foremost. Clean them out with some electrical spray cleaner and apply a very small amount of dielectric grease to the connections.

Maybe part of your wiring harness was pinched or melted, causing faults to the AFM and TPS. Seconded that the code 25 is most likely just a result of the other 3.

After you fix the 24, 31, and 41, you might end up needing a new O2 sensor. They can burn out when AFR is out of whack for too long due to heat (lean) or soaked in gas (rich).

Best of luck to you Let us know what you find