Funny Idle
Thread Starter
Racer
Joined: May 2006
Posts: 369
Likes: 0
From: Chicago IL
Funny Idle
My idle gets jumpy every so often. Out of no where in traffic today while stopped for 1 minute it dropped down to 400 rpm and went right back up. I have newer plugs, wires, and battery. Could it be a coil? How do you test those? Any other ideas?
Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
I would love for someone to chime in about this. I have an 01' that I bought in Dec. with high miles to be my daily driver. It does the exact same thing. It does it whether the A/C is on or not. Also, I noticed that mine will do it coming to a stop and it seems to be at it's worst when I am stopped, let my foot up on the brake & let it idle forward...It will dip to 400 rpm. like every 2 seconds while idling forward. It doesn't die, it just annoys the hell out of me 
... Anyone experts have any input?
... Anyone experts have any input?
Thread Starter
Racer
Joined: May 2006
Posts: 369
Likes: 0
From: Chicago IL
After reading and thinking today I'm thinking possibly a bad ground.
It doesn't happen often on my car but like for you it's annoying. It almost sounds like I have an aggressive cam, but not that much of a lope. It acts like if someone just put the a/c on. Another possibility I'm thinking is the alternator? I have no codes besides my passenger check valve error.
It doesn't happen often on my car but like for you it's annoying. It almost sounds like I have an aggressive cam, but not that much of a lope. It acts like if someone just put the a/c on. Another possibility I'm thinking is the alternator? I have no codes besides my passenger check valve error.
Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
After reading and thinking today I'm thinking possibly a bad ground.
It doesn't happen often on my car but like for you it's annoying. It almost sounds like I have an aggressive cam, but not that much of a lope. It acts like if someone just put the a/c on. Another possibility I'm thinking is the alternator? I have no codes besides my passenger check valve error.
It doesn't happen often on my car but like for you it's annoying. It almost sounds like I have an aggressive cam, but not that much of a lope. It acts like if someone just put the a/c on. Another possibility I'm thinking is the alternator? I have no codes besides my passenger check valve error.
Melting Slicks
Joined: Jun 2004
Posts: 3,439
Likes: 6
From: Newark, DE
St. Jude Donor '06
Assuming you haven't made any recent changes, I would check the intake tract. First, verify that you don't have any air leaks - check all the band clamps for tightness, verify the coupler/airbridge don't have any tears or cracks (in particular if you have a pre-2001, ensure the IAT grommet is still intact), make sure the allen bolts on the manifold are all equally tight (but not too tight... the torque spec is only 89 in-lbs). Second, clean the MAF and/or throttle body if they are dirty or oily.
Burning Brakes
Joined: Apr 2006
Posts: 833
Likes: 1
From: long island NY
St. Jude Donor '06
Assuming you haven't made any recent changes, I would check the intake tract. First, verify that you don't have any air leaks - check all the band clamps for tightness, verify the coupler/airbridge don't have any tears or cracks (in particular if you have a pre-2001, ensure the IAT grommet is still intact), make sure the allen bolts on the manifold are all equally tight (but not too tight... the torque spec is only 89 in-lbs). Second, clean the MAF and/or throttle body if they are dirty or oily.
Thread Starter
Racer
Joined: May 2006
Posts: 369
Likes: 0
From: Chicago IL
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Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
Assuming you haven't made any recent changes, I would check the intake tract. First, verify that you don't have any air leaks - check all the band clamps for tightness, verify the coupler/airbridge don't have any tears or cracks (in particular if you have a pre-2001, ensure the IAT grommet is still intact), make sure the allen bolts on the manifold are all equally tight (but not too tight... the torque spec is only 89 in-lbs). Second, clean the MAF and/or throttle body if they are dirty or oily.
Cool, I will do the checks tomorrow! I have seriously got my fingers crossed about it being one of these "easy" fixes...Thanks for the suggestions!!
Le Mans Master
Joined: Dec 2001
Posts: 5,705
Likes: 548
From: St. Peters MO
C7 of Year Finalist (stock) 2019
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Assuming you haven't made any recent changes, I would check the intake tract. First, verify that you don't have any air leaks - check all the band clamps for tightness, verify the coupler/airbridge don't have any tears or cracks (in particular if you have a pre-2001, ensure the IAT grommet is still intact), make sure the allen bolts on the manifold are all equally tight (but not too tight... the torque spec is only 89 in-lbs). Second, clean the MAF and/or throttle body if they are dirty or oily.
Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
I work 3rd shift so I haven't had a chance to "crack it open" yet to check the air bridge or MAF yet. I am off this week so I will have time to do so.
I did want to add to this by saying that when I fire up the Vette, in about a mintue or so of idling, I hear a "air leak" sound from the front portion of the engine. It sounds like "ssssssssssssss" for a lack of better verbal description. None the less, I will tear it apart on Tuesday & report back to you guys with what I find! Thanks guys!!
I did want to add to this by saying that when I fire up the Vette, in about a mintue or so of idling, I hear a "air leak" sound from the front portion of the engine. It sounds like "ssssssssssssss" for a lack of better verbal description. None the less, I will tear it apart on Tuesday & report back to you guys with what I find! Thanks guys!!
Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
OK guys, check it out.
I went through everything in the front that was described to check out. I found nothing...
Instead, I was getting new brake pads put on at my bud's shop & found that my transmission pan has been leaking...looks like passenger side of pan but it had leaked back over the center of my rear leaf spring...
With that being said, I now am convinced that this idle issue is caused by the tranny...When I come to a complete stop it idles fine...When I let my foot off the brake & idle forward, that is when it seems that the tranny can't decide if it wants to be in neutral or 1st gear...When I do decide to take off, it hesitates before kicking into 1st...
Does this make sense to anyone? It sure does seem like this is what is happening since it is the ONLY time that it does it.
How much should I expect to spend at the dealership to get the gasket & transmission fluid changed? I don't really have means to lift the car at the house to do this on my own so I guess I will have to rely on the dealership to do it for me...
I went through everything in the front that was described to check out. I found nothing...
Instead, I was getting new brake pads put on at my bud's shop & found that my transmission pan has been leaking...looks like passenger side of pan but it had leaked back over the center of my rear leaf spring...
With that being said, I now am convinced that this idle issue is caused by the tranny...When I come to a complete stop it idles fine...When I let my foot off the brake & idle forward, that is when it seems that the tranny can't decide if it wants to be in neutral or 1st gear...When I do decide to take off, it hesitates before kicking into 1st...
Does this make sense to anyone? It sure does seem like this is what is happening since it is the ONLY time that it does it.
How much should I expect to spend at the dealership to get the gasket & transmission fluid changed? I don't really have means to lift the car at the house to do this on my own so I guess I will have to rely on the dealership to do it for me...
Le Mans Master
Joined: Feb 2006
Posts: 5,267
Likes: 40
From: Phoenix AZ
Just to clarify, an auto trans does not go into neutral when you stop. It will go from whatever gear you were in (lets say 60 mph in OD) and downshift itself into first gear when you come to a stop. You could shift it into neutral and the idle should be higher.
Maybe you have a low fluid level in the trans that could cause a problem?
Or you could check the brake booster and hose.
Maybe you have a low fluid level in the trans that could cause a problem?
Or you could check the brake booster and hose.
Instructor
Joined: Apr 2004
Posts: 152
Likes: 0
From: Knoxville Tennessee
It's fixed!! 
I could not find anything wrong with the car, going by what was suggested for me to check so I did the "C5 idle re-learn" proceedure & it worked! Idles like a champ & smooth as glass now!!
Thanks guys for all of your input & hopefully if anyone else has this problem, it will work for them as well!!!
I could not find anything wrong with the car, going by what was suggested for me to check so I did the "C5 idle re-learn" proceedure & it worked! Idles like a champ & smooth as glass now!!
Thanks guys for all of your input & hopefully if anyone else has this problem, it will work for them as well!!!
Melting Slicks
Joined: Nov 2005
Posts: 2,296
Likes: 156
From: Clayton New Jersey
It's fixed!!
I could not find anything wrong with the car, going by what was suggested for me to check so I did the "C5 idle re-learn" proceedure & it worked! Idles like a champ & smooth as glass now!!
Thanks guys for all of your input & hopefully if anyone else has this problem, it will work for them as well!!!
I could not find anything wrong with the car, going by what was suggested for me to check so I did the "C5 idle re-learn" proceedure & it worked! Idles like a champ & smooth as glass now!!
Thanks guys for all of your input & hopefully if anyone else has this problem, it will work for them as well!!!