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Engine Revs Unintentionally

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Old Dec 24, 2009, 02:08 PM
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Question Engine Revs Unintentionally

Mod, please move if this is in the wrong place. Thank you.

While driving on the freeway, even though my foot is steady on the gas, my engine goes through audible cycles. It revs and then is normal and then revs and is normal, etc. This even happens when I'm stopped at a stop light not even stepping on the gas. It doesn't go to a very high rpm, but it doesn't sound right. Any ideas?
Old Dec 24, 2009, 02:13 PM
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When driving on the hwy does your speed increase with the engine RPM's?
Old Dec 24, 2009, 02:14 PM
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How much do the RPMs change?
Old Dec 24, 2009, 09:38 PM
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bad MAF sensor?
Old Dec 25, 2009, 01:46 PM
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vac leak maybe. did it just start doing this out of the blue or did you change something?
Old Dec 25, 2009, 01:49 PM
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Vac leak would be my guess, something in the EGR system maybe. I had this problem on my honda. Gradual revving of the throttle, turned out to be the EGR line or solenoid. Check to make sure everything is plugged in and no cracks in the lines.

Merry Christmas
Old Dec 25, 2009, 01:57 PM
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I've noticed this problem when my engine is still cold too. When I first start my engine it idles at 1500 rpm once it warms up it drops to about 1000 rpm. But then when I'm at a stop light not even steping on the gas my rpms go up from 1000 rpm to about 1350 rpm. After like 4 seconds it stops and goes back to normal at 1000 rpm. It stops doing this after the engine is fully warmed up. Is this normal?
Old Dec 25, 2009, 02:09 PM
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RPM #'s ???
Old Dec 25, 2009, 02:15 PM
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Originally Posted by Betty
I've noticed this problem when my engine is still cold too. When I first start my engine it idles at 1500 rpm once it warms up it drops to about 1000 rpm. But then when I'm at a stop light not even steping on the gas my rpms go up from 1000 rpm to about 1350 rpm. After like 4 seconds it stops and goes back to normal at 1000 rpm. It stops doing this after the engine is fully warmed up. Is this normal?
that sound like a vac leak to me. hondas do it all the time cause the fast idle valve gets stuck part of the way open causing the idle to surge.
Old Dec 25, 2009, 02:21 PM
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^^^ are the rpm numbers weird?
Old Dec 25, 2009, 02:26 PM
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Thank you for your help, how woud I go about checking this valve? Is it an expensive fix?
Old Dec 25, 2009, 02:48 PM
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im having the same issue...when its cold my idle would go up and down from 1000 to a little under 1500 and would keep doing it for a while then stop...what should i check?
Old Dec 25, 2009, 02:57 PM
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Originally Posted by Betty
Thank you for your help, how woud I go about checking this valve? Is it an expensive fix?
im not sure if evo's have a valve like the honda dose. i was just using that as an example. it seams like they are doing the exact same thing tho
Old Dec 25, 2009, 02:58 PM
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^^^ Tim85851 that is my exact issue. I just started noticing mine. How long has yours been doing it for? Any help on fixing the issue.
Old Dec 25, 2009, 03:03 PM
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Iac?


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