Tracking idle/throttle problem
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Joined: Aug 2009
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From: Acworth GA
Tracking idle/throttle problem
Idle will intermittently hang while coasting to a stop at 1500rpm and sometimes will climb up to that or even higher then fall to correct idle as soon as I come to a stop. Does it mostly while driving slow(traffic, parking lots, etc). Idles fine as long as im not moving. Makes it very annoying to drive.
It will also rise on its own while coasting. This will happen clutch in or out. This began after ported MSD and ported stock throttle body(which I think is the culprit).
Mods before this happened: cam, wcch heads, headers, halltech cai
Video showing it rising while coasting...this is just coasting downhill clutch in and out. No throttle input from me and only letting off the brake.
If I can get my hands on a stock TB, I will swap out to see, but is there any other way to track this down? I thought vacuum leak, but the way it does it while coasting makes me think otherwise.
Edit: Car is a 2008 Z06 if that matters
It will also rise on its own while coasting. This will happen clutch in or out. This began after ported MSD and ported stock throttle body(which I think is the culprit).
Mods before this happened: cam, wcch heads, headers, halltech cai
Video showing it rising while coasting...this is just coasting downhill clutch in and out. No throttle input from me and only letting off the brake.
If I can get my hands on a stock TB, I will swap out to see, but is there any other way to track this down? I thought vacuum leak, but the way it does it while coasting makes me think otherwise.
Edit: Car is a 2008 Z06 if that matters
Last edited by ChevyCobb; May 7, 2017 at 03:06 PM.
Instructor
Joined: May 2015
Posts: 229
Likes: 22
From: NJ
Idle will intermittently hang while coasting to a stop at 1500rpm and sometimes will climb up to that or even higher then fall to correct idle as soon as I come to a stop. Does it mostly while driving slow(traffic, parking lots, etc). Idles fine as long as im not moving. Makes it very annoying to drive.
It will also rise on its own while coasting. This will happen clutch in or out. This began after ported MSD and ported stock throttle body(which I think is the culprit).
Mods before this happened: cam, wcch heads, headers, halltech cai
Video showing it rising while coasting...this is just coasting downhill clutch in and out. No throttle input from me and only letting off the brake.
https://www.youtube.com/watch?v=ojLgG1KKD5g
If I can get my hands on a stock TB, I will swap out to see, but is there any other way to track this down? I thought vacuum leak, but the way it does it while coasting makes me think otherwise.
Edit: Car is a 2008 Z06 if that matters
It will also rise on its own while coasting. This will happen clutch in or out. This began after ported MSD and ported stock throttle body(which I think is the culprit).
Mods before this happened: cam, wcch heads, headers, halltech cai
Video showing it rising while coasting...this is just coasting downhill clutch in and out. No throttle input from me and only letting off the brake.
https://www.youtube.com/watch?v=ojLgG1KKD5g
If I can get my hands on a stock TB, I will swap out to see, but is there any other way to track this down? I thought vacuum leak, but the way it does it while coasting makes me think otherwise.
Edit: Car is a 2008 Z06 if that matters
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Joined: Aug 2009
Posts: 718
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From: Acworth GA
Hmm, well its been close to 600 miles now. After I made the first post I went out for a quick drive on the highway.
At about 65mph in 5th gear, I pressed the clutch and the rpm rose to over 2000 and then fell to 1500 and stayed there.
Really annoying....
I have a bluetooth obd2 connector and the torque app. Does anyone know if it might be able to show something abnormal? No codes and no CEL.
At about 65mph in 5th gear, I pressed the clutch and the rpm rose to over 2000 and then fell to 1500 and stayed there.
Really annoying....
I have a bluetooth obd2 connector and the torque app. Does anyone know if it might be able to show something abnormal? No codes and no CEL.
Last edited by ChevyCobb; May 8, 2017 at 02:21 PM.
Racer
Joined: Dec 2016
Posts: 438
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Hmm, well its been close to 600 miles now. After I made the first post I went out for a quick drive on the highway.
At about 65mph in 5th gear, I pressed the clutch and the rpm rose to over 2000 and then fell to 1500 and stayed there.
Really annoying....
I have a bluetooth obd2 connector and the torque app. Does anyone know if it might be able to show something abnormal? No codes and no CEL.
At about 65mph in 5th gear, I pressed the clutch and the rpm rose to over 2000 and then fell to 1500 and stayed there.
Really annoying....
I have a bluetooth obd2 connector and the torque app. Does anyone know if it might be able to show something abnormal? No codes and no CEL.
Thread Starter
Pro
Joined: Aug 2009
Posts: 718
Likes: 7
From: Acworth GA
Mine was a vacuum leak. The grommet at the brake booster had a large tear in it. Easy fix but still confirmed with a DIY smoke tester. If you are having the same thing it very well could be a leak if the tune is right.
Still went with a NW102 anyway though when it was all said and done.
Still went with a NW102 anyway though when it was all said and done.
Last edited by ChevyCobb; Nov 9, 2017 at 03:37 PM.
Drifting
Joined: Aug 2016
Posts: 1,273
Likes: 205
From: Kansas City MO
I've been chasing down this same issue for far too long and want to do the diy smoke tester. I'm 99% certain it's a vacuum issue.
Did you do the paint can method? If so did you burn something in the can or heat oil to produce smoke? Where did you hook the smoke line into the vacuum system? Lastly did you use a Tech 2 to open any evap solenoids? I have one but havent used that function yet.
Any advise you have to offer would be very, very much appreciated.
Edit: I'm also curious why you mentioned there being no difference based on clutch position. I sometimes feel like that does make a difference on mine, but I think I'm really just going crazy worrying about it. Would that indicate a different potential issue if the clutch did affect idle in your opinion?
Did you do the paint can method? If so did you burn something in the can or heat oil to produce smoke? Where did you hook the smoke line into the vacuum system? Lastly did you use a Tech 2 to open any evap solenoids? I have one but havent used that function yet.
Any advise you have to offer would be very, very much appreciated.
Edit: I'm also curious why you mentioned there being no difference based on clutch position. I sometimes feel like that does make a difference on mine, but I think I'm really just going crazy worrying about it. Would that indicate a different potential issue if the clutch did affect idle in your opinion?
Last edited by doomi; Nov 9, 2017 at 08:03 PM.
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Joined: Aug 2009
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From: Acworth GA
Yep I did the paint can and just used mineral oil to heat up a ribbon wick wrapped in wire. I hooked mine up to the hose going to the brake booster after replacing the grommet. Take off intake to the TB and just put some plastic wrap over the TB held on with a rubber band.
Re: clutch position - I was trying to rule out any rotational issues or some other underlying clutch problem because it had been replaced recently to that coming up. I would bet it wouldn't be related for yours too.
Re: clutch position - I was trying to rule out any rotational issues or some other underlying clutch problem because it had been replaced recently to that coming up. I would bet it wouldn't be related for yours too.
Drifting
Joined: Aug 2016
Posts: 1,273
Likes: 205
From: Kansas City MO
I really appreciate your reply.
I did the paint can set up today and could not locate a source of a leak. However I didn't seal the TB, so I'll attempt again tomorrow. Did you order an OEM booster grommet or happen to find one at a local store? I'm looking at a couple of auto shop websites and don't see anything.
Also, are you an LS2? I'm trying to figure out how I'd hook the smoke tester into the hose going into the brake booster without using a T. That hose is connected to the back of the intake manifold on LS3 and is a bear to get to.
I did the paint can set up today and could not locate a source of a leak. However I didn't seal the TB, so I'll attempt again tomorrow. Did you order an OEM booster grommet or happen to find one at a local store? I'm looking at a couple of auto shop websites and don't see anything.
Also, are you an LS2? I'm trying to figure out how I'd hook the smoke tester into the hose going into the brake booster without using a T. That hose is connected to the back of the intake manifold on LS3 and is a bear to get to.
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