Aloha...brand new to the group and glad to be here. I have a 1993 PU 4x4 22RE. Bought it 8 months ago and it has ran great. Only 100,000 miles and one owner. Anyhow last month I was driving and the check engine light came on and the truck lost power. I replaced plugs, cap, TPS. The truck still runs the same. What is intersting is that when I crank it, it runs fine for a few minutes, then the check engine light comes on. I jumped it with a paperclip but it gives no codes....the check engine light just stays on. Again when it runs great, she hauls but as soon as the light comes on, it starts running with less HP and going downhill, she backfires. Another thing is that a week ago she was running awesome for an hour after I changed the plug wires (again) and as I was going, she just shut off suddenly. I pulled over and tried cranking for a few minutes but all she did was turn over. I waited a few more minutes and she fired right up....running fine...then it did it again but she started right back up and ran fine. Next day I cranked her up and she ran fine for a bit then the check engine light came on and I am back to no codes....Bad ECU??

 

You need to preform (two) voltage checks, when the light is lit, to determine if the power is coming from the ECU or a short to positive somewhere in the dash.. Check ECU output pin, check cluster wire, both while unplugged.

It should always flash the "all clear" (no codes) when the jumper is in place, its worth the effort to verify this signal is reaching the ECU and not something simple like a grunched up diagnostics port.

 

Thanks for the input.....and yes it does flash no codes when its running right. I have removed the ECU and checked the terminals. I cranked it earlier and she ran great for a few minutes but then the idle dropped and she went back to "safe mode". I did'nt mention before that when she runs right and I unplug the TPS, the idle goes up. Now if she is running in safe mode,and I unplug the TPS, there is no effect.

 

Some codes are not stored, you can't turn the engine (ECU power) off. I don't recall which ones these are offhand, I'm leaning towards a oxygen sensor code or maybe knock signal (timing retard beyond limits). Both of those would yield poor performance.

Be sure what you are posting puts "us" as close to in front of the vehicle as possible, always reread your posts, its better to give to much input in almost all cases.

So to be clear.

when you jumper the diagnostics mode it consistently flashes (about once per second)?

 

Thanks for the advice and yes...it flashes about once a second. Again the check engine light will stay on and throw no codes when it starts running like crap. I will check the o2 and knock sensor as well.