My 96NA 2+2 idles at 1500 when ever I come off the throttle. Doesn't seem to matter if I am just puttering around or really leaning into it. Hot or cold. When I tap the accelerator *every so slightly* the idle drops to 1200, then to 800. I have checked the linkage and the throttle bodies are indeed on the stops when it is idling high, and the throttle movement to is less than a 1/8" inch and then it goes to "normal" idle.

 

Mine too, I figured it's normal

 

check this thread out. it might help you
https://www.zdriver.com/showthread.php?t=9914

 

It's the AAC. Try adjusting the idle control screw. Unplug the AAC and turn the screw to adjust. If that only fixes it and it goes back up, probably a bad AAc.

 

it could be a bad iaa unit(which is where the aac is) or air regulatory unit

 

yea... same here... i have a 90 tt and it idles at 1500rpm.... i though it wasent normal... but i guess it is....

 

I'm going out on a limb here...

At first, I did the SeaFoam thing and saw some benefit. Ran DeepCreep through the throttle bodies and got it to idle again, but in a week or so it started to idle high again pretty consistently.

Got me thinking... I HAD added a POP Charger air filter and trusted the salesman that it did NOT need oil treating. What it if DID and I was sucking dirt into the MAF/TB/intakes so cleaning was only temporary?

Cleaned and oiled the filter. Recleaned the TB's with DeepCreep. Got brave/desperate and briefly shot DeepCreep into the *GASP* MAF. Reassembled everything. Now I get the idle down to 800 after an understandable 5-8 second high idle when I come off the throttle. Every time.

Strikes me that the intakes need to be SQUEAKY-clean before these guys will idle down. In addition to everything else that can keep them idling high. Maybe I just got lucky. Thoughts?

 

About a month later, still idles down like a champ. Let me know if you try the SeaFoam or the DeepCreep, ok?

http://www.seafoamsales.com/motorTuneUpTechGas.htm (SeaFoam)
http://www.seafoamsales.com/deepCreepTech.htm (DeepCreep)
http://www.knfilters.com/clningacc.htm (Recharger Filter Care Service Kit)

 

Two months later and still idles ~800rpm. I was working on the car recently, checking connectors, testing this sensor and that one. I remembered something that may be of help to some with high idles.

If the TPS is set so the "Throttle Closed" circuit is not closed when you have the throttle closed, the car will idle up to about 1500-1800. As soon as it closes, and after it blows some last fumes past the O2 sensors, the idle drops.

I believe that a slight rotation to the RIGHT will cause it to close earlier. Only a few degrees of movement are needed to make the adjustment if this is your problem.

If you have Consult interface, it will display the status for you and make adjustment a breeze.

 

The TPS must be adjusted properly. If it's not, then you will have problems. The output voltage at idle should be .4 volts. At WOT it should be 4 volts. If the TPS is within spec, then the problem is something else.

 

I was referring to the second sensor on the TPS, it is a 2 position normally closed switch that opens as you crack the throttle open. If the TPS is adjusted so that this switch never closes, then you may experience the problem that I described.

Thoughts?

 

Mine does the 1500 rpm idle sporadically, but it''ll always drop back to the 700-800 rpm range eventually. I do notice it mostly after starting off when the engine is cold. I mean the engine is up to operating temp, but it has only been there for a few minutes. Or when coming off the freeway after a good 10-20 mile run at 80-90 mph.

I, myself, speculate that this is from my slightly leaky injectors. I can't remember if I posted here or elsewhere about a situation that I had and came to the conclusion that I have one, or more, leaky injectors. I'll explain this if you want..........

The rpm theory is that the O2 sensors/ecu sense a rich condition and increase the idle and lean the mixture to burn off the excess fuel. :chug:

 

I'll go along with that. That could be one of my problems. Won't be with the new injectors, but that could help explain the high idle I had + high hydrocarbons, and the ECU code for the open injector circuit.