Well, I have been having some idling and low speed drivability problems, so I checked the TPS voltage and it was only going from .65 - 3.8 volts. (This was having it adjusted as far down as I could get it) I ordered a new TPS, and this one does the same thing! What could be going on?

 

Follow the procedure to set the minimum air in the tech articles and see if that won't allow you to adjust it down a bit more (and buy you more room on the top to go over 4.0v).

Just a thought, but what readings can you get out of it with it not attached to the TB? And is the TB opening all the way at the 3.8v reading?

 

It'll go up to 4.3 volts not attached, and yes it is opening all the way. In my service manual, it says that anything below .96 V will be set as 0% throttle, up to 4.6 V at WOT.

Is there any way to tell if the computer is recognizing WOT, like by the diagnostic light flashing while driving in diagnostic mode, for example?

 

Then I'd do the min air procedure and see if you can set the TPS adjustment far enough to get over 4V.

I don't know how to read % TPS without a data logging program like TunerPro or DataMaster (I use both)

 

CHECK YOUR IDLE CONTROL MOTOR. IT MAY BE STICKING AND CAUSING YOU THE PROBLEM.

 

As for the IAC - be forewarned, the steps shown in a data log are NOT a report of where the IAC actually is, they are only where the ECM told it to go to.

I had a bad IAC that wasn't really moving even though the data logs were showing movement. Took a while to figure that one out and swap it out.

 

You'd have to use a scantool to find out what TPS voltages the ECM is getting back. If it has the proper voltage ranges off the car on a test bench, then its gotta be something on the TB. You could reset the stock IAC and clean it, I recently had to replace mine. I think the correct pintle measurement is 1.108 inches or 28 mm from tip to flange. Install it, then get in the car and tap the gas, car on for 5 seconds, off for 10 seconds, then back on. Unless someone has jacked with the minimum idle before, I dont see a need to adjust it. I didnt have to adjust mine and I replaced both TPS and IAC (this is on an 89 L98).