vacuum leak!!

woops I see that you checked the plate definitely closing above.

Check your dashpot.

As mentioned before it's been cleaned and lubed so it's definitely not sticking...

In addition I haven't put it back on since I cleaned the throttle body.



So anyway, I performed a test with the idle by-pass valve by putting a piece of tape over the port in the throttle body. Not to my suprise this affected my idle; I had to back out the Idle mixture screw (to where it used to be when all was well) and it idled just fine when it was warmed up.

I guess I'm going to fork out some dough for a replacement or find another throttle body assembly to test it with first. I'll keep this thread updated...

Update...

I scored a 93 throttle body with a TPS for 60 bucks! (Car-parts.com) which I'll be getting next week.

I'm just going to swap the entire TB over and give that a shot, with a little luck this will take care of it.

Even if it doesn't it's not a total loss since I'll have an extra TPS laying around.

Another Update...

I cleaned up the junk yard throttle body and got it installed today... It runs exactly the same as before, eliminating the Idle Air Control Valve and the TPS as the problem.

I'm running out of ideas at this point and I'm not sure what else to check... <img src="/forums/images/graemlins/scared.gif" alt="" />

Just had the same problem with my 93 xcab this last spring. I replaced the dashpot and the problem went away.

Here's an update on this annoying issue.

I took off and cleaned the EGR and verified that all the vacuum lines were routed correctly. My idle is still fubared - even worse with the colder temperatures.

Here's a re-cap of what's been done...

TPS adjusted and working correctly
Fresh coolant - burped properly
New Thermostat
Vacuum lines routed correctly
Coolant Temp sensor replaced
Throttle body thoroughly cleaned
Throttle body swapped with another one (to test the idle air control valve)
Dashpot cleaned and NOT sticking
Throttle cable lubed and NOT sticking
Timing set at 5 degrees
No check engine codes
Idle screw is IN the entire way

And like before; if I'm crawling or idling for a long period of time (15 minutes or so) my idle will gradually drop to where it's supposed to be - I even have to adjust my idle screw out a few turns.

Any other thoughts?
Triple check the vacuum lines?
Is there an Air Temp sensor on or near the AFM?

Yep:
- http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml#AFMtesting

I found the problem tonight.. Wow, am I ever relieved!

Here is it - clogged coolant passage from using 'Stop-Leak' in the past. This prevented fresh / warm coolant from making it to the temp sensor... The ECU was only sensing that the engine was cold which in turn increased amount the fuel = high RPM's and a very rich condition.

Thanks for all of the suggestions guys - hope this helps anybody in the future with a similar problem.