Idle High
Thread Starter
Instructor
Joined: Nov 2009
Posts: 141
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From: Huntsville Alabama
Idle High
I have a modified '07 Z06 that seems to have an issue with idling high. The car has a killer bee intake, torquer 110 cam, kooks headers, no cats and a corsa exhaust. I first take the car out it seems to idle just fine at around 900 RPM however after driving for a bit it likes to idle high, sometimes up to 1400 RPM.
The behavior is that when I'm approaching a stop, I let off the throttle and put the car in neutral, and it idles down to 900 RPM nicely while the car is moving. As I finally come to a complete stop the car will idle up to 1300+ RPM sometimes for a few seconds and then drop down. However, it seems that after driving around town for a while it will idle up and never settle down to 900. After doing this for a while I'll get a CEL (P0507 - Idle Air Control System RPM Higher Than Expected).
Now, here's the thing. The car has a locked PCM currently so I can't really get in there to check the idle settings, but it may also be a mechanical issue. I'm guessing that a vacuum leak might be part of the issue, but I'm kind of thown off by the idle jump when coming to a stop. Any thoughts on what I can check mechanically while I'm trying to get the PCM unlocked?
The behavior is that when I'm approaching a stop, I let off the throttle and put the car in neutral, and it idles down to 900 RPM nicely while the car is moving. As I finally come to a complete stop the car will idle up to 1300+ RPM sometimes for a few seconds and then drop down. However, it seems that after driving around town for a while it will idle up and never settle down to 900. After doing this for a while I'll get a CEL (P0507 - Idle Air Control System RPM Higher Than Expected).
Now, here's the thing. The car has a locked PCM currently so I can't really get in there to check the idle settings, but it may also be a mechanical issue. I'm guessing that a vacuum leak might be part of the issue, but I'm kind of thown off by the idle jump when coming to a stop. Any thoughts on what I can check mechanically while I'm trying to get the PCM unlocked?
Thread Starter
Instructor
Joined: Nov 2009
Posts: 141
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From: Huntsville Alabama
The car was modified when I bought it but I believe the only change after the tune was the intake. Once I get the PCM unlocked I'll look at the tables and see what's up. I did some checking last night and there are a couple of things that I found. First, the hose clamp that is on the throttle body is not very tight and I can actually turn the intake by hand. It's not going to come off but it's not snug either so I'm going to find another clamp and see if that helps. Second, the U-shaped PCV hose seems loose to me where it connects to the intake manifold. That is, the hose seems like it is stretched open and isn't really making a good seal. I thought about trying to put on a hose clamp but I don't think I could get to it to tighten it down. Is this a known issue or am I just imagining things? I could pull it off again and take a picture but basically it just seems like the inside diameter is a bit too big.
Last edited by juyanith; Jan 23, 2011 at 08:28 AM. Reason: Clarification
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Any vacuum leak can cause idle issues. Yes, the PCV fitting is a known issue. They dry rot, get soft and fail frequently. Fix all the known air leaks and see if that makes any difference..
BC
BC
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
The car was modified when I bought it but I believe the only change after the tune was the intake. Once I get the PCM unlocked I'll look at the tables and see what's up. I did some checking last night and there are a couple of things that I found. First, the hose clamp that is on the throttle body is not very tight and I can actually turn the intake by hand. It's not going to come off but it's not snug either so I'm going to find another clamp and see if that helps. Second, the U-shaped PCV hose seems loose to me where it connects to the intake manifold. That is, the hose seems like it is stretched open and isn't really making a good seal. I thought about trying to put on a hose clamp but I don't think I could get to it to tighten it down. Is this a known issue or am I just imagining things? I could pull it off again and take a picture but basically it just seems like the inside diameter is a bit too big.
The hard plastic lines for the EVAP system do seem loose, but they usually seal up fine.
Thread Starter
Instructor
Joined: Nov 2009
Posts: 141
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From: Huntsville Alabama
I also replaced the hose clamp where the intake connects to the throttle body and it's got a nice seal now. I'll just have to see if the symptoms go away.
2nd Gear
Joined: Feb 2023
Posts: 2
Likes: 0
High Idle
I have a modified '07 Z06 that seems to have an issue with idling high. The car has a killer bee intake, torquer 110 cam, kooks headers, no cats and a corsa exhaust. I first take the car out it seems to idle just fine at around 900 RPM however after driving for a bit it likes to idle high, sometimes up to 1400 RPM.
The behavior is that when I'm approaching a stop, I let off the throttle and put the car in neutral, and it idles down to 900 RPM nicely while the car is moving. As I finally come to a complete stop the car will idle up to 1300+ RPM sometimes for a few seconds and then drop down. However, it seems that after driving around town for a while it will idle up and never settle down to 900. After doing this for a while I'll get a CEL (P0507 - Idle Air Control System RPM Higher Than Expected).
Now, here's the thing. The car has a locked PCM currently so I can't really get in there to check the idle settings, but it may also be a mechanical issue. I'm guessing that a vacuum leak might be part of the issue, but I'm kind of thown off by the idle jump when coming to a stop. Any thoughts on what I can check mechanically while I'm trying to get the PCM unlocked?
The behavior is that when I'm approaching a stop, I let off the throttle and put the car in neutral, and it idles down to 900 RPM nicely while the car is moving. As I finally come to a complete stop the car will idle up to 1300+ RPM sometimes for a few seconds and then drop down. However, it seems that after driving around town for a while it will idle up and never settle down to 900. After doing this for a while I'll get a CEL (P0507 - Idle Air Control System RPM Higher Than Expected).
Now, here's the thing. The car has a locked PCM currently so I can't really get in there to check the idle settings, but it may also be a mechanical issue. I'm guessing that a vacuum leak might be part of the issue, but I'm kind of thown off by the idle jump when coming to a stop. Any thoughts on what I can check mechanically while I'm trying to get the PCM unlocked?
Thanks
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Melting Slicks
Joined: Apr 2019
Posts: 2,504
Likes: 1,166
From: Northern Wisconsin
Z06 comes with dual-level vacuum-powered muffler sound modes (RPO code NPP). When your exhaust system was changed over, was the existing vacuum actuation addressed such that the vacuum source wasn't left open to the atmosphere?
2nd Gear
Joined: Feb 2023
Posts: 2
Likes: 0
Thanks for the input.
~p
