very fast idle

[bull52]

i have a 91 metro that i can't slow the idle down below 30 mph i have tried all i know which isn't much when it comes to a throttle body. It will idle fine when first cranked but after touching the gas pedal it starts all over again, i changed throttle bodys from another and the problem is still there,please help

[$400chevymetro]

Will it idle down by hand with the throttle linkage?

[bull52]

no it does not i have play in the throttle cable,this problem started all at once then it went away for a few days now back again,i have checked all vaccum lines and the idle screw is all the way in and my gas mileage went to about 15 mpg, if i had had hair i would pull it out.

[Crvett69]

on the back of the intake by firewall there is a solenoid with 2 rubber hose connected to it. first make sure the hoses are there and havn't fallen off. if everything looks fine find the one that goes from solenoid to the bottom of throttle body. pull the end off the solenoid and plug it with a pencil or bolt or something. leave other end hooked to throttle body. if car idles down that solenoid is defective. can leave hose plugged and adjust idle with the air bleed screw on side of throttle body. never mess with the set screw on butterfly

[RossT]

Had this happen to me last summer on my 91, it was as above, the ISC valve. Make sure that the vacuum hoses are all hooked up properly to it. If a hose is off, it will suck air into the engine and cause a very high idle. I have found that whith no power to the ISC you should not be able to blow thru it ( in the same direction as vacuum is sucked into the engine). If you can blow thru yours, it could be bad. I always grab these from the junk yard whenever I can, cause they are a common failure part on our cars.

[bull52]

thanks for the reply i tried that and can see what you mean it really takes off when the vaccum line is removed,but that didn't help. I did notice that when you rotate the throttle by hand and let it pop back that it does idle down, you don't feel it in your foot but can feel a little hard spot when done by hand,could this be build up on the butterfly. Thanks so much

[Crvett69]

did you try plugging that line and see if the idle dropped?

[$400chevymetro]

Originally Posted by bull52

I did notice that when you rotate the throttle by hand and let it pop back that it does idle down, you don't feel it in your foot but can feel a little hard spot when done by hand,could this be build up on the butterfly. Thanks so much

........Since it will idle down by poping it back as you said you might try cleaning linkage with a good spray injector cleaner. Then lube with Liquid Wrench it's better at freeing stuck parts than WD40. then keeping working and see if that hard spot goes away.Try to work Liquid Wrench into throttle cable it may have a litte rust in it.

[bull52]

i just finished spraying the linkage and cable,gonna let it sit for a few days,this is the last weekend of hunting season,can't miss that. Thanks for all the help i have been driving geo's for a long time,by the end of this year i will have nearly one million miles divided between 3 metros. Thanks again for all the help. P.S. I did plug the line it made no difference