1994 is 400 high idle

[Pierre goodrow]

hi, I'm new on here so let me introduce myself, I'm Pierre.  Just bought a 94 ls400 w/130,000 miles and she idles at 1200 rpm so I can't go thru emissions.  Any suggestions would be greatly appreciated!

thx

[paulo57509]

Try looking for vacuum leaks.

Is your check engine light on?  Check for trouble codes.  You might have a coolant temperature sensor that's reading cooler than normal.

[Pierre goodrow]

Thakns, I have no check engine light and I have checked for vacuum leaks and found none

[RX400h]

This is a slightly generic answer so you may want to verify that your car has the same components listed.

Quote

The below lists common causes of high idle and in each case, the appropriate vehicle system, components, and parts involved would be inspected, removed for repairs, and/or replaced as needed.

Faulty Fuse: In the majority of vehicles, engine idle speed is controlled via an idle control valve (ICV). A faulty or blown fuse in other electronically controlled systems can cause the Idle Air Control (IAC) motor to malfunction, leading to a higher than normal engine idle speed.

Faulty Idle Air Control Valve (ICV): Some cars are equipped with an idle air control valve to maintain idle speed. This part can malfunction due to excessive carbon buildup in the intake manifold.

Vacuum Leak: On any engine, a vacuum leak will cause a high engine idle as the oxygen sensor detects lean operation and the engine computer then tries to compensate, which can result in abnormal idle. Malfunctioning Throttle: A malfunctioning throttle system can cause both a high or low idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit. Computer Malfunction: If the powertrain control module is malfunctioning, idle speed may be affected.