Prolonged High Idle Upon Start

[brendanr279]

Hey, guys. I have a problem with my idle. When I start the car (92 legacy L) the idle is high (1500) for five minutes or more. If I don't let the car warm up substantially, the idle stays high and the rpms hardly drop at all when I shift (it's a manual). I've had an old honda accord before that had an erratic idle upon start, I had to clean the "fast idle thermo valve". It just involved removing a spring loaded ball-thing with some plastic components from a cylinder housing and cleaning with brake parts cleaner. Is this something that I can do to my Legacy? Or what's going on here? Thanks

[Legacy777]

1,500 rpm is about normal for high idle upon initial startup. It should drop down relatively quickly after driving. What sort of temperatures does this occur in?

 

How does the car drive once it has warmed up and idle is normal?

 

Does it take a long time for the car to reach normal operating temperature?

 

If the car takes a long time to warm up, and your mileage is so so, you may want to look at replacing the coolant temp sensor, which controls a lot of the ECU's functions related to temperature, including AFR and idle speed control.

 

If that seems ok, you can try spraying brake cleaner in the idle air control valve tube or use some sea foam spray to help ungunk the IAC valve. Worst case, you remove the IAC valve to clean it or replace it.

 

This is the IAC valve.

 

http://www.main.experiencetherave.com/subaru/images/injectors/DCP_2470.JPG

[gregB]

I was experiencing the same condiiton and it just started. High ~1500 rpm at start, outside temp 40-50°F. If I blip the pedal it settles down to "normal" idle speed.

 

Had the valve pictured above off and cleaned it with MAF cleaner. Not much junk came out. The rotating part was not completely closed, but would move against the spring if pushed. Should the rotating part normally be fully closed, open or some where in between? Can it be adjusted?

 

I did put in a new temp sensor also, cleaned out the vaccum lines etc.

 

Ideas?

[CoupedUpSubie]

OP, which engine do you have? The older 1.8s have a different IACV then the 2.2s and 2.5s.

[Fairtax4me]

The "door" in the idle control valve will sit in different places depending on temperature. The ecu also cycles the valve opening as the engine is running to contole idle speed. After a while the valve gets crudded up and sticks.

A good shot of Throttle body cleaner through the large hose usually cleans it up.

[Legacy777]

I was experiencing the same condiiton and it just started. High ~1500 rpm at start, outside temp 40-50°F. If I blip the pedal it settles down to "normal" idle speed.

 

Had the valve pictured above off and cleaned it with MAF cleaner. Not much junk came out. The rotating part was not completely closed, but would move against the spring if pushed. Should the rotating part normally be fully closed, open or some where in between? Can it be adjusted?

 

I did put in a new temp sensor also, cleaned out the vaccum lines etc.

 

Ideas?

 

As mentioned, there's actually two doors on the rotary type IAC valve, the main electromagnetic one, and a temp dependent one. The electromagnetic one should sit about half way open/closed. They're supposed to come calibrated from the factory, but if someone has messed with it or whatever, you can rotate the top electrical portion of the valve to try and get it back into working order.

[Legacy777]

OP, which engine do you have? The older 1.8s have a different IACV then the 2.2s and 2.5s.

 

All the north american first gen legacies had the 2.2. Only the 90-91 MT's had the older reciprocating valve compared to the newer rotary style valve.