Howdy,
Long time listener, first time caller.

Got a 1991 22RE with a slightly rough idle and periodic shudder. Shudder goes away and idle smooths when TPS is disconnected.

- Checked TPS resistance and adjusted with feelers, all good
- New Denso O2 sensor
- Checked for vacuum leaks
- Throttle body cleaned & gaskets replaced
- New OEM plugs
- Timing is backed off to about 3-4 to ease pinging
- Idles steady around 750-780, just shakier than usual lately.

Read sb5walker's write-up on TPS's role in computation, still wondering what about the computer running in Open Loop would smooth the idle & shudder when the TPS seems fine.
Apologies if I've missed something when searching the forums, a lot of TPS info to process..

Thanks folks!

 

How positive are you that the TPS is adjusted correctly. The TPS is a frustrating creature on these engines without alot of practice. The TPS can be out of adjustment by just .004 of an inch. If you are not absolute 100% sure it is correct, I almost guarantee that is the culprit. TPS is the starting point and if its not right, everything will be wrong.

Final statement, the TPS takes lots and lots of practice too get right and only with that practice can one determine if the TPS is bad or out of adjustment.

 

 

Is the throttle stop adjusted correctly? It can throw off tps measurements. I also cleaned out my intake manifolds + egr valve and it seemed to help out my idle smoothness.

 

Throttle stop is adjusted too, contact plus a 1/4 turn. Intake could definitely use a deep clean, but the issue came on suddenly. Have noticed it seems temp dependent; truck idles fine at start then gets rougher as it warms. Sounds & feels like the time I forgot to clamp the intake boot back down, but I've checked pretty thoroughly for vac leaks..