I posted something about this about a month ago but the problem didnt go away. I have a 77 l28 fuel injected in my 240z. After cleaning up the fuel rail/injectors and also the throttle body my engine developed a idle problem. When you push on the gas the rpms go high and never come back down. The linkage and everything is ok. The only way to get the rmps to come back down is if you put it into gear or to shut off the engine and turn it back on. (but once you hit the gas again...it comes back) I found that if i move the wires around and rotate the throttle valve switch the idle changes. I havnt been able to find any vacuum leaks...So can i conclude that the throttle body is bad? All the moving parts including the butterfly are working OK. I already ordered the performance big bore throttle body. Is there any way i can test this stuff before i spend more money on a new throttle body? Thank You

I know I saw this post... I thought I saw some responces to it .... Without the engine running check to see that the throtle linkage and air flow meter etc are not binding...

Backup. disreguard that . If you do not have a book that describes the parts of your fuel injection system do not even try to work on this... Get a factory manual, or at least a chiltons guide.. It sounds like either something is binding, or you have a failed sensor... I will stop there because this is not my strong suite. But if you plan to service your oun car start with a book. You cannot replace the convenience, or accuracy of the information in a good service manual. It is likely the problem you have is listed in the troubleshooting section.

I think I replied to this before, but just in case. Did you use the tachometer from the donor car? There is a resistor or something like that in the back of the FI cars tach that affects the idle speed. If you have the original tach in there it will not have that, and this may be part of the problem.

If not there, it may be in the potentiometer on the side of the air flow meter.

A Factory service manual is almost mandatory when working on FI, it will explain all the test procedures and how to test all the sensors without taking a lot of them off the car. The Chiltons manuals and others are nowhere near as good as a Factory manual. If you can find one, get one, you will be glad you did.