High Idle

[my1990300zx]

Hello I have a very high idle 1,000 to 1200 I adjusted the TPS and IACV and it wont come down what should i do next thanks

1990 300zx non turbo

[Rogue One]

Please STOP creating duplicate threads!

[evildky]

You either have tension on your throttle cable, improperly adjusted throttle stops on your TB's or a vac leak if everything else is good.

[DCaff300ZX]

If the IACV doesn't lower the idle, then a vacuum leak is your issue that must be found. Most likely culprits are the larger hoses attached to the IACV as the get brittle/split from removal, and then if not check any/all of the smaller vacuum hoses, and the intake hardpipes for cracks/broken nozzles (has happened to me).
If this doesn't help then perhaps the IACV itself is bad (also happened to me) or you have another issue with the CTS connector or PTU harness (corrosion).
Top 5 areas to look, hope this helps!

[my1990300zx]

thanks you for helping you have been great in the past answering my tech problems. I guess I should mention when I install the upper intake plenum I kept the same gasket on it looked great with no cracks or worn also the reason I didn't replace it I didn't want the new one to move when installing . So did I screw up do I have to take this nightmare apart again ??

[DCaff300ZX]

I can't say that's a positively bad thing or root of your problems, but is something that you really don't want to do (reuse gaskets) because of this very question should a problem occur. The problem of course is that testing is difficult at best and provides a probability concern that is in addition to the problem which may or may not be your actual problem.

At this time I would say that your best move is a clinical, time consuming but important test of the entire system using the OSM and it's procedures as best you can. I have done this myself and know it's possible, and is also somewhat of a PITA but most importantly, leaves you with a pretty firm grasp of where you stand regarding what is working, not working, or undecided needing further digging. There are SO many things related to idle and can cause problems that seem similar to one another but are not related directly, or are indirectly related to another area such as the AT and other engine/car controls, so you need to get that all sorted out especially considering you indicate you have done major work to the car.
There is also a sticky at the top of the Z32 section that goes into idle issues, and TT.net has some help topics related to idle in their tech section as well.
Good Luck!

[my1990300zx]

Thanks again let you know if I find out what the problem is take care.