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How do you adjust idle speed
Topic Started: Jul 30 2010, 02:03 PM (4,105 Views)
vikasintl
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I have 1994 geo metro 2 dr manual 3 cylinder and idel was rough and shaky badly.
So I went to mechanic and he said idle is too slow and he adjusted the idle speed ( I don't know how) but later I found that "there is no adjustment for the idle speed on this type of engine. There is a stop for the throttle linkage, which is held in place by a lock nut. But that is not intended to be moved. Moving that stop will upset the air/fuel ratio" and will require resetting both the computer's throttle switch and the idle air bypass screw. And if that is not done, it will create a chronic rough idle. "

So do you think that mechanic moved lock nut? to increase the idle speed? and that has created more problem than solving rough idle because my problem is still there even after he increased idle speed.

If I need to rest computer throttle switch and idle air bypass screw how can I do that?
Also what could be cause of rough idle? actually rough idle smooth out when I accelerate just a little


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slander
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Tech Certified

Your car has ICS. 1994 and newer has the ICS.

Check your timing.
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DesmondGhostRider
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Is that a challenge?

I have a 94 and I adjusted it so that it would still run the AC when it turns on. Sadly 94 and up dont have the easy adjust screw.

Remove Air Box
Look to the right of the now exposed hole.
There is a tiny screw with a bolt on it. The screw will have a place to put a allen wrench in it.

Thats the throttle adjust. I set mine a bit higher when I redid the vaccum lines, cleaned the egr, and replaced the pcv switch.
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Bad Bent
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Facetious Educated Donkey

Welcome to the forum, vikasintl! :coffee

I'd like to know how long you have had the car? How many miles? The last two changes/service to the engine? Is the Check Engine Light on? Can you do a compression check? Click Here.

The rough idle could be caused by a loose/old plug wire, a bad plug (gap), distributor contact buildup, poor compression, clogged PCV/EGR valve, or it could appear as the engine idle when it's the motor mounts. Could be fuel related; injector, EVAP, fuel filter. The 3 cylinder engine idles rougher than a 4 cylinder.

Can you ask the mechanic what he did without letting him touch the car again?

Sounds like the Throttle Stop Linkage is what BryanTheGhostRider adjusted and it worked for him. That opens the butterfly valve in the Throttle Body allowing more air in. Mine (changed by the PO) is adjusted so the butterfly (gas pedal) does not stick. There is an actual, recessed, Idle Adjust Screw above and to the right of it. but my Chilton manual says 1994 and above could be emissions (clogged Catalytic converter?) or a sensor.

In short something caused the idle to go rough and a simple idle adjust is not the cure. The ECM computer can/may compensate for a lot of out of tolerance conditions until it gives up and flashes you.
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captain1.0


Do a compression test.
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vikasintl
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slander
Jul 30 2010, 02:46 PM
Your car has ICS. 1994 and newer has the ICS.

Check your timing.
how do I confirm if my car has ICS or fast idle air valve ...I was reading haynes manual and it said 89 to 94 has fast idle air valve and not ICS...please advice...
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