really...wow but it ran fine when the tps was unplugged?? coincidence?

 

If he unplugged the TPS, the ECM should have put the system into limp home mode. If his fuel pump could not deliver fuel at sufficient pressure and the computer was in normal mode, the ECM would have set fuel pressure at X and the pump couldn't keep up. If in limp home mode, the pressure was set to some lower level the pump might have been fine. Best guess.

What should really worry him is that he UNPLUGGED HIS TPS AND DIDN'T GET A CODE. That's not good. He should have got code 41 after just half a second of having that thing unplugged.

You really should check your CEL

 

Makes sense. I will check with him today about his cel. Thanks for the replys

 

The computer does not control fuel pressure. It's controlled by a vacuum operated fuel pressure regulator.

 

BMcEL, do you have a solution?

 

Mine was absolutely a coincidence although I did replace my TPS because the original failed to spec out on the ohm meter. However, the new TPS set perfectly did not cure my problem. My fuel pump was 100% the reason for the rough running, power loss, and throttle cut off. My guess is that the rust in the tank would suck up into the pump as the sock filter was gone and cause the truck to run bad. Then in the time that it would take me to get out, pop the hood, unplug the TPS, and finally restart the truck, the rust would fall back out, clear the pump, and it would run good until it sucked up another chunk of rust.

Here's what the pump looked like:


My truck did throw codes, it just wasn't pertinent to the previous discussion.

Good luck with yours rbmoomba. 4Crawler's website was invaluable in all the electronic parts testing as was the service manual.

 

Yes, and there is a VSV operated by the ECM that increases fuel pressure during cold starts. So yes, it's vacuum operated but the ECM has some control over the vacuum pressure.

Cmayer, that pump looks terrible! Your theory sounds absolutely plausible. It's still pretty strange that your CEL doesn't come on when you run with an unplugged TPS. It should throw a code as soon as the vehicle is running if you unplug it.

 

Oh, it did throw a code every time it was unplugged, I just ignored it. Now that it's all back together I cleared the codes and the engine is happy. Now I need to make the drive train happy again and enjoy the runner.