1988 T2, All Stock

In trying to fix my lumpy/bouncy/incorrect idle I've pretty much driven myself in circles and can't quite pin point what to change without "adjusting" the other setting I just tried to get back into spec.

If I want to just start from a clean slate on this idle thing, in what order should I adjust the TPS, BACV screw, and Idle Adjustment? (And variable resistor, if necessary?) so that they don't throw one another out of spec?

Also, noob question(s), is the TPS only supposed to be actuated during the first few degrees of movement of the throttle? TPS's on cars I've had before this were usually of a wiper/rotor type and not the plunger one these cars have, so I'm a bit lost!

Is the TPS ever supposed to give an Open Loop (infinite resistance) reading when you're setting it?

 

it will take several rounds of adjustment to get everything in sync if things have been altered.

All of this must be done with the initial set coupler jumped.

With the car fully warm, adjust the hard idle stop screw as per the FSM instructions.

Then set the TPS to 1K using a meter.

Then adjust the BAC if necessary.

The TPS should neve go infinite. If it does, it's bad. And yes, it's only a 1/4 range TPS.

 

Oi I was afraid of that haha, aw well I seem to be making some headway. It still seems a little "lumpy" though, it bounces around 750 about +-100RPM in either direction, I did try searching for any vac. leaks though I didn't find any, are there common places for hoses or connections to leak that I can check?

I had a Multimeter that for some reason didn't auto-range itself, and actually cut out when OHM's went over 999, so it fooled me into thinking I had a bad TPS this whole time.

with a cheap new radio shack one things are going much easier!

Thank you for the help, AC

 

Realistically, vacuum leaks could be anywhere. I find that a spray bottle of water helps to locate them.

It is also possible that the variable resistor is a bit lean and thus causing the idle to hunt. Once you have totally eliminated the possibility of vacuum leaks, you can turn that screw just slightly richer and see if it smooths out.