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Wierd rpms hovering/idle issue

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Old Jan 14, 2009 | 10:37 AM
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Default Wierd rpms hovering/idle issue

Hey guys,

Recently, when throwing the car into neutral when rolling up to a stop light, I intermittenly have some rpms/idle issues I was hoping you guys could help me with. I got dyno tuned about a year ago, and this just recently started. Basically, when in neutral, and rolling at about 10-15 mph....maybe less maybe more.....on occasion, my rpms will rise to about 2k and hover there until I come to a complete stop. Sometimes, the rpms never fall to idle, they just come down to 2k and hover there until I come to a complete stop. Any ideas as to what could cause this?

In addition I thought Id mention that sometimes my rpms dip below the set idle, sometimes pretty low to the point where the engine sounds like its starving.

I did recently have some high rpm missed shifts could this be a contributing factor, although my memory tells me the hovering rpms started prior to the missed shifts

Last edited by 04ctsvfl; Jan 14, 2009 at 10:50 AM.
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Old Jan 14, 2009 | 04:58 PM
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Anyone want to even throw darts at the issue (ie possible catalysts for this problem?
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Old Jan 14, 2009 | 07:34 PM
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Hmm, according to your mod list you don't have any "real" mods except for the headers. You're also DBW right? I'm guessing you have an LS6? Typically symptoms like yours are intake airflow related, maybe you have a leak is all I can think of. Try pulling your battery and seeing what happens, that will cause your idle trims to reset and may temporarily fix the issue.
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Old Jan 14, 2009 | 10:12 PM
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thanks buddy, I will try that tomorrow and post any results
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Old Jan 14, 2009 | 10:16 PM
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hmm with your mods, you shouldnt have that kind of issue ever. I would say vac leak somewhere maybe? Or fuel pressure issue?
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Old Jan 14, 2009 | 10:51 PM
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try the line off of the pcv to intake. my ls6 did that today and i change the 2" hose and stopped the 2k idle. now it just wants to die and lopes at time at a light. on to another problem
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Old Jan 15, 2009 | 04:41 AM
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Bent pushrod?
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Old Jan 15, 2009 | 08:42 AM
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wouldnt it be happening 100% of the time if it was a bent pushrod?
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Old Jan 15, 2009 | 09:46 AM
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Short of any vacuum leaks as mentioned before, pulling valve covers and checking pushrods is an easy check- you did mention the over-rev's.

Throwing darts as requested.
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Old Jan 15, 2009 | 04:46 PM
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I would vote for a vacuum leak as well....easy way to check is with the car running, spray some brake clean/carb cleaner around the intake,tb, injectors, pcv hoses, vacuum lines. If the RPM's increase....you have a leak. Good luck finding the problem.
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Old Jan 16, 2009 | 10:46 AM
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Thanks guys, troubleshooting will start over the weekend.

ss1875 - will seafoam do the trick to find a leak?
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