kodalee

I have a 93 lt1. when its cold it idles around 600-800 as soon as it gets warm it idles around 1800-2000. I have fixed the wiring around the map sensor, the iac sensor, the tps sensor and the iat sensor. I have cleaned the iat sensor, the iac sensor and the throttle body. I have also replaced the tps sensor. what can be causing this problem?

Injuneer

Which trans, auto or manual - determines what the correct idle speed should be?

When the coolant is cold, the ECM raises the idle speed. If "cold" is, for example, 24*F, idle speed should be 800 RPM for an A4 in gear, 1,000 RPM or an A4 in neutral and 1,000 RPM for an M6. The stock tach typically reads 100-200 RPM above actual idle speed. Since the ECM looks at coolant temp to set idle speed, a faulty CLT sensor could cause a problem.

Idle is controlled by the ECM, using the idle air control motor (IAC is not a "sensor"). If the IAC motor is faulty, or the harness circuits are faulty, the ECM can't control the idle. There are no DTC codes for a faulty IAC. Here's a method to check the IAC (93 will be similar to 95):

http://shbox.com/1/iac2.jpg

Have you scanned the ECM for codes:

http://shbox.com/1/dlc2.jpg

Have you checked the throttle cable/linkage to make sure it isn't hanging open when the engine heats up?

Injuneer

Wouldn't if be nice if once in a while people would come back and post to acknowledge that they even read the answer....... maybe note whether they were able to solve their problem??????

Total lack of courtesy.