High idle ... sticking idle valve...

[nkemp]

My idle started going high ... again. It would often idle near 2,000rpm. No obvious air leaks. As I was thinking about it I started thinking about how the idle control motor/valve could flow enough air to raise the idle that far. I used the pigtail that I have for the valve and banged the valve both ways while the engine ran (high). First the valve worked, one way barely raised the idle speed, the other chocked the engine off (as expected). When I restarted the idle came in perfect. But a short while later, it was high again. So I wiggled some wires and no impact. Then I tapped the idle motor with a tool and the idle droped to near purr-fect. A little later, high idle. Tapped the motor and with each tap the idle came down a bit to purr-fect again

I've exercised the valve before, banging it to both extremes and did so with spray cleaner and penetrating oil to clean it up (It is a rotating vane that could gum up with muck). At this point I don't know if:
- The valve is gunked up
- This is the valve's failure mode
- The controller cannot flow enough current to drive the motor out of stuck position
- There is a wire problem limiting the current to the motor (and I'm using a lower current version motor)

I offer this up as info to others out there that have high idles. My next move might be to put in another motor/valve but I HATE messing with that brass idle air pipe that goes into the bowels of the intake manifold.

[Jonathan]

If you disconnect the entire connector on the passenger side of the idle ECU behind the driver's seat, it will keep the idle right at 2,000 RPM. When you said yours sticks near 2,000 RPM, it made me think of this. Could be part of your problem or it might not be. You might add this sort of test to your troubleshooting to figure it out.

[nkemp]

The idle can be anywhere in the 1,000 - 2,000 range so I don't think it is bulkhead connector related. Besides, that doesn't explain why tapping/hitting it makes it come back into normal idle.

[Rich]

My idle started going high ... again. It would often idle near 2,000rpm. No obvious air leaks. As I was thinking about it I started thinking about how the idle control motor/valve could flow enough air to raise the idle that far. I used the pigtail that I have for the valve and banged the valve both ways while the engine ran (high). First the valve worked, one way barely raised the idle speed, the other chocked the engine off (as expected). When I restarted the idle came in perfect. But a short while later, it was high again. So I wiggled some wires and no impact. Then I tapped the idle motor with a tool and the idle droped to near purr-fect. A little later, high idle. Tapped the motor and with each tap the idle came down a bit to purr-fect again

I've exercised the valve before, banging it to both extremes and did so with spray cleaner and penetrating oil to clean it up (It is a rotating vane that could gum up with muck). At this point I don't know if:
- The valve is gunked up
I offer this up as info to others out there that have high idles. My next move might be to put in another motor/valve but I HATE messing with that brass idle air pipe that goes into the bowels of the intake manifold.

Maybe it is indeed gunked up again and maybe your cleaning so far has not been thorough enough. Here is how to really clean that puppy, also a way to check the continuity of the electrics, taken from a page out of this site LINK: k-jet.org/articles/information/k-jet-debugging-guide/ (http://www.k-jet.org/articles/information/k-jet-debugging-guide/):


A sticking idle air motor will often cause a “surging” when driving – your car will accelerate when it’s not supposed to – and/or a “hunting” idle, where your car just can’t seem to find the right idle. A hunting idle might range from 500 to 2000 rpms, and just keep going up and down.

An idle air motor that just plain won’t work can be detected by trying to start the car and having another person “feel” the idle air motor. It vibrates (buzzes) when it is running. You can also hook it up to a battery or booster pack to test it. Supposedly the middle terminal on the plug is positive and the two outside terminals are negative, but I have been unable to verify this other than just hearsay. An idle air motor that is REALLY dead will actually emit white smoke when you try to use it.

The idle air motor can be cleaned out by removing it from the car completely and spraying it out with carb cleaner. Wear gloves and goggles! This stuff can burn the bejeezus out of your skin and eyes! Spray a bunch of carb cleaner in it and plug both of the ends. Now, shake it up as much as you can – up and down and roll it between your hands like you were trying to make a long snake out of Play-doh like in kindergarten. When you roll it, you should be able to hear it clicking back and forth. If you can’t hear anything moving in there, keep cleaning it or get a new motor. Make sure to shake out all of the excess carb cleaner and let the thing dry for a bit before you re-install it.

Another way to test the idle air motor is to measure the resistance with your multimeter. A good motor should read +/-20 ohms resistance between any two pins that are next to eachother and +/-40 ohms resistance between the two outside pins.

The idle air motor can be cleaned out if it is not too damaged. The most common way to do this is to detach the motor from the car and spray it out with carb cleaner. Fill the motor with carb cleaner and plug both openings in it. Shake it up and roll it back and forth in between your hands like you are making a ‘snake’ out of clay. You should hear it clicking back and forth. Repeat the cleaning process several times, drain the motor, and then allow it to dry for an hour or so.

[DMCMW Dave]

I swapped one for test purposes yesterday (twice) . No reason to disconnect the brass pipe at all. Just loosen the clamp on the back hose and pull it out.


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