toofly1999

recently purchased truck from friend who couldnt figure out what was going on with truck so he sold it to me (cheap)! anyway truck has only one code, 31. which my fantastic Haynes manual tells me is AFM signal or vacuum switch signal. Symptoms are truck idles ok but stumbles and runs rough off of idle with power loss! feels like EGR problem to me but thats just a guess on my part! so today checked for voltage at ECU on VS and VC circuits both had seemingly steady voltage 5-7 volts that dropped as rpm was increased! (I have exact values written down, if needed, going off memory) so im assuming AFM is ok! that leaves vacuum switches and my Haynes manual doesn't seem to provide testing procedure or even accurate component locations for vacuum switches! I tried to find FSM for this truck off of sticky on here but seems links are old or have moved! Haynes manual by trying to cover so many models is confusing and not much help! any ideas or know where i can find FSM? any suggestions appreciated!

NickMc

I have a 93 with the same code and symptoms along with backfiring. I'm just about to pull the trigger on an AFM but wish I had more confidence that it was really bad.
Here's a link to the manual http://www.ether3al.com/93fsm-mobile/

Nick

toofly1999

Hey nick, I was able to find FSM at our local library and was able to use copier to get pages i needed! Turn out i had two problems; first was had a bad AFM (air flow meter); second was had bad injector which didnt throw a code but the FSM has testing procedures for all sensors, switches and components of truck all you need is an ohm meter and i bought a LED test light from harbor freight which has two leads one for positive terminal of battery and the other to ground side of battery and then you can probe any wire and it will tell you if wire is hot or is a ground! (very helpful) plus they are computer safe for checking your ECU (computer)! Truck is fixed now and running great! Parts weren't cheap $240.00 for AFM and $150.00 for injector (ouch) but truck is fixed and im stoked! Hope this helps you and good luck! Craig

NickMc

Thanks Craig and congrats, seems like many have long, frustrating chase of poor running engines. I'm going to get one of those little lights. My replacement AFM arrived today and that was the problem, thank god. Runs great now. All my plugs were uniformly black so I didn't suspect an injector. I got my AFM from AutohauzAZ for 132 plus 13 tax and 28 core which I should get back. All the usual local suspects were 250 ish. Now, on to the clutch, then shocks then timing chain maybe, then exhaust. . . front end overhaul. But it's cool, the 2 wheel drive, std cab,. short bed is a sporty little truck when it's running right.

toofly1999

Thats awesome nick congrats to you as well! wish I would have got my AFM from where you got yours! that was a good price! but oh well looks like engine was either rebuilt recently or swapped out recently as compression test showed all four cylinders were in the 172 to 175 psi range so she runs real strong! only other issue ive found was its got a bearing whine in the 5 speed trans and sounds like its on the input shaft to me but it is hard to hear it so I figure it just started recently so im gonna let it develop and not get to excited about it as Ive had yotas that have had that whine the whole time i owned them! Ive got an 85 rte 4x4 (turbo) truck that was left on the property that i purchased by the previous owner! I didnt know anything about this truck or any of the turbo models.so did a little research and tore the head off mine and found blown head gasket and i suspect a cracked head! sent it to machine shop and it was all bad, block, head, crank everything was no good so thats where it is now and after researching and finding out they only made them for two or three years i suspect there was a design flaw and they abandoned the line so afraid to spend the money on an engine that has known issues! I want to drop a 22R or 22RE in it but I live in california and our smog laws are pretty strict! dont know if it would be allowed or not! i suspect it could be done but how much is it gonna cost and could I get it out of the thing if i were to sell it! but I really like that body style and is built like a tank so would love to put her back on the road if it didnt cost to much or cost my marriage! lol btw thx for link to the manual mines a 92 but might be useable ill have to look in to it! did they have other years there where you got it? See ya on the Happy Trails! Craig