Engine's been running rough when it's warmed up. With the engine running I disconnected the TPS. I then reconnected it still with the engine running. There's a sound the engine makes, like the throttle engaged and it seems to get a squirt of fuel, and the RPM's jump significantly. I then drive it , it runs like a new car. However, if I turn the engine off and restart it, its back to its hard idle again. With the engine running I disconnect the TPS and then reconnect it and it runs great, although the idle seems really high even with the screw turned all the way down.

Can anyone explain this?

 

Have you pulled the codes yet? These injection systems are funny things on these trucks. Not seeing the tps can put it into a limp home mode where it has to make assumptions about the throttle position. Then when you plug it in, it sees the tps, and starts making adjustments and "learning" about the signals from the tps and how best to run the engine. It's "best way" to run the engine does not always run the engine correctly if there are other problems.

I have played with this a lot on my 86 ranger, and have learned some things the hard way on it. It has a bad idle control motor, and I refuse to pay $170 for it. So I have been monkeying around with it, and have the IAC actually blocked off on my ranger. It makes it cold natured when I first start it up, but I have messed with the rest of it to make it run right after it's warmed up.

-You need to clean out the throttle body area and the IAC motor. Do it the best you can without getting any cleaner up in the motor part of the IAC. Clean all around the throttle plate and the passages.

You need around .8v coming from the throttle position sensor when the throttle is sitting on the screw. I would pull the codes to make sure you do not have a bad TPS. Since you have been unplugging it, you might need to take the battery cable off for a minute or so to erase any codes, then drive it and see what happens. You have been messing with the throttle screw, and I can't fault you for that, Most have been messed with already. But you need to get it back in the ballpark position, the one that will give you .8v + or - on the wires coming from the TPS. I know from experience it will not run right if it's over 1v.

 

Yeah, Dave. I hear you. The tps is new. The IAC is new and the throttle body has been thoroughly cleaned with carb cleaner. Still, I suspect the tps is not working correctly.

I did pull the codes. At KOEO I read 11-11. At KOER I got a 13, 77, and 25. It was interesting. When I went to pull the codes with KOER the engine rpm'd really high and I got a reading of 4 (4 cylinders for an 8 cylinder engine) and then the rpm's calmed down after about 90 seconds and I got the above readings.

 

Yes, I got to your other post and see you did get some codes. 13 is because the throttle adjustment is open too much, 77 is because you didn't blip the throttle, and I thought you said the other one was a 23 knock sensor code?

 

Actually, it was a 25. What do you mean to blip the throttle? Does that mean to rev it?