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it just started doing it. i have a '94 GS and on a cold start, my engine revs up to 3000rpms then continues to rev up and down between 2000 and 3000 for about 3mins until engine warms up. <p>does anyone know the cause of this? is this happening to anyone else? some feed back would be nice, thanks.

Believe it or not, you might want to check the coolant level and make sure it's topped up. If the coolant chamber in the throttle body is not full of coolant, the cold idle can do crazy things. People who do the "coolant bypass mod" often experience nutty idles.<p>I assume you've seen no check engine light?

My car does the same exact thing. Sometimes it does it when i park the car after a trip on the highway. I believe its caused by bypassing coolant flowing through the throttle body.

mikes absolutely right. I did the bypass and my idle was JACKED in the winter. I put the hoses back on and its all solved. I see that cashmoney you have the bypass done. Thats the reason you have the prob i can guarantee it. Check ur coolant level if you dont have the bypass done

I have the TB coolant bypass and I have no jacked up idle... I just adjusted it when I initially did it.. now on cold starts it revs to 1500 or so rpm.. then as it warms up slows down to about 6-700rpm..<p>if it has only just started doing it then I would look elsewhere.. <p>have you made any changes to your engine recently? when did you do your TB bypass? any major weather changes??<p>fill us in on a bit of background and we should be able to get a better idea..

Could it be that your winters in Sydney just aren't as cold as Canada/Chicago/Virginia? I have an idea that the coolant to the throttle body is there to prevent icing, so it seems logical the lack will be felt in cold weather - maybe most in wet, cold weather.<p>I was wondering about plumbing in a bypass with T pieces and a stop valve, so that you could close the bypass in winter - any views?

yea.. that's a point.. i guess it doesn't really get that cold here in winter.. <p>i wonder has it all of a suddent gotten really cold? because there is not really any reason for it to all of a sudden happen like that..

Thanks for the feed back guys, i had a feeling that it had something to do with the TB/coolant bypass. <p>my step father tells me it might be a vaccum leak. before winter hit i had a K&N cone filter put in, i must of forgot to plug that little hose that usually goes the to filter box. i'm guessing that little hose connects to the TB somehow. <p>i plan to fix the problem on my day off. thanks again.

no problem.. let us know your result..