[88SlowBird]

   
85 Turbo Coupe 5 Speed

What else will cause a hanging idle other than the TPS or vacuum leaks?

If I blip the throttle quickly it will come down to 1000 but as soon as you press the throttle again it will stick at 1500-2000 RPM


The throttle body is clean and it always closes all the way so I don’t suspect anything is hanging up physically

TPS has been sweep tested no dead spots and it’s set to .85 and I’ve verified it always goes back to .85 when the throttle is shut
(I don't believe it needs to be exactly 0.95 or 0.99 like some say it just needs to be below 1.0)

I cleaned the IAC and did a proper base idle reset but that didn’t seem to help

0 Vacuum leaks I've inspected and sprayed brake clean on every line and all around the intake with no change

tested the ECT resistance hot and cold and its in spec

tested the VAM VAT sensor and it's in spec (VAM air temp sensor)

VAM possibly causing this? ECU caps bad?

[TurboRay]

.
For shíts & giggles ~ drive it with the IAC unplugged, to see if the problem ceases. <shrug>

[dan_xr4]

Have you checked if your closed loop fuel control is working properly ? 

Does the oxygen sensor switch back and forth at the 1000 RPM point and at the 1500 RPM-2000 RPM point ?

Is the ignition timing the same at the 1000 RPM point and at the 1500 RPM-2000 RPM point ? (30 degress BTDC)

One problem might be that your engine has less friction than the calibration is expecting to see.

[88SlowBird]

ended up figuring out the throttle body blade wasn't closing all the way

cleaned the throttle body and greased the linkage now it doesn't stick

[TurboRay]

The throttle body is clean and it always closes all the way so I don’t suspect anything is hanging up physically.

<stickpoke>