Hi new to the site been looking through its very good .
I have a question what is the iac my cab 1990 automatic the engine rpm at idle whines up and down what could be my problem i have to adjust over 1500 rpm to run but if i drive it idles bad have to gas if not it shuts down appriciate the help

 

Its an Idle Air Control (IAC) valve.

How an Idle Air Control Valve Works | eHow.com

Get it checked out.

https://volkswagenforum.com/forum/ne...gnature-34185/