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2004-2007 Cadillac CTS-V General Discussion Discussion, Rough Idle Question in Cadillac CTS-V Series Forum - 2004 - 2007; I know from previous threads that the V runs rough at idle. However, recently I have noticed that I get ...
  1. #1
    Art138's Avatar
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    Rough Idle Question

    I know from previous threads that the V runs rough at idle. However, recently I have noticed that I get an intermittent shake much like the AC compressor kicking on in a low compession engine car (spaced about 30 seconds apart); does not appear to be an RPM drop but sligh wobble on the needle. I only have 8,500 miles on the car so I discounted the plugs.....is this a normal trait of this engine????

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    darkman's Avatar
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    Re: Rough Idle Question

    Quote Originally Posted by Art138 View Post
    I know from previous threads that the V runs rough at idle. However, recently I have noticed that I get an intermittent shake much like the AC compressor kicking on in a low compession engine car (spaced about 30 seconds apart); does not appear to be an RPM drop but sligh wobble on the needle. I only have 8,500 miles on the car so I discounted the plugs.....is this a normal trait of this engine????
    My first guess is that nothing is wrong. This engine shimmers occasionally. If it gets worse, my next guess would be a motor mount.

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    Art138's Avatar
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    Re: Rough Idle Question

    thks, will keep an eye on it.....

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    Re: Rough Idle Question

    Art... my car used to have a rather severe rough idle which did indeed to turn out to be a broken motor mount... Now i have all new motor mounts but i still feel as if my motor idles a little rough. I am going to take it up to the dealership soon and see what they have to say. I am young (20) so im still learning about the motor but my pops is a mechanic and the excessive rough idle worries him as well.

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    Naf's Avatar
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    Re: Rough Idle Question

    Hey,

    Ok you guys seem to always jump to the worse stuff before lookin at the obvious.

    You say you have 8500mi on the car, i would rule out almost all major components like motor mounts, they dont go bad that quickly.

    If possible check your MAF sensor, make sure its clean. From there check the inside of your intake manifold. There might just be a bit too much gunk in the intake, where when its strugglin with the A/c it effects your idle.

    I would then do a simple ignition check. Make sure the wires are fine, reading about the same amount of Ohms +/- 10-50 on stock is fine.

    Then check the plugs, you may have a bad one, check 7 & 8...They normally spoil first.

    If all that showes no sign of issues, then you think the motor mount, ot other hardware related issues. You know it may even be a bad o2 sensor. It is directly related to the engine function. You have to think from start to finish then consider surroundin hardware.

    I always start from the air inlet and work all the way to the exhaust. If i dont see or find any issues then i work to other related issues that may cause similar symptoms..

    Start simple then go complicated...You will find that 99% of the time its the simple things that go wrong first...

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    Re: Rough Idle Question

    Quote Originally Posted by Naf View Post
    Hey,

    Ok you guys seem to always jump to the worse stuff before lookin at the obvious.

    You say you have 8500mi on the car, i would rule out almost all major components like motor mounts, they dont go bad that quickly.

    If possible check your MAF sensor, make sure its clean. From there check the inside of your intake manifold. There might just be a bit too much gunk in the intake, where when its strugglin with the A/c it effects your idle.

    I would then do a simple ignition check. Make sure the wires are fine, reading about the same amount of Ohms +/- 10-50 on stock is fine.

    Then check the plugs, you may have a bad one, check 7 & 8...They normally spoil first.

    If all that showes no sign of issues, then you think the motor mount, ot other hardware related issues. You know it may even be a bad o2 sensor. It is directly related to the engine function. You have to think from start to finish then consider surroundin hardware.

    I always start from the air inlet and work all the way to the exhaust. If i dont see or find any issues then i work to other related issues that may cause similar symptoms..

    Start simple then go complicated...You will find that 99% of the time its the simple things that go wrong first...
    Well Said

  8. #7
    darkman's Avatar
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    Re: Rough Idle Question

    Quote Originally Posted by Naf View Post
    Hey,

    Ok you guys seem to always jump to the worse stuff before lookin at the obvious.

    You say you have 8500mi on the car, i would rule out almost all major components like motor mounts, they dont go bad that quickly.

    If possible check your MAF sensor, make sure its clean. From there check the inside of your intake manifold. There might just be a bit too much gunk in the intake, where when its strugglin with the A/c it effects your idle.

    I would then do a simple ignition check. Make sure the wires are fine, reading about the same amount of Ohms +/- 10-50 on stock is fine.

    Then check the plugs, you may have a bad one, check 7 & 8...They normally spoil first.

    If all that showes no sign of issues, then you think the motor mount, ot other hardware related issues. You know it may even be a bad o2 sensor. It is directly related to the engine function. You have to think from start to finish then consider surroundin hardware.

    I always start from the air inlet and work all the way to the exhaust. If i dont see or find any issues then i work to other related issues that may cause similar symptoms..

    Start simple then go complicated...You will find that 99% of the time its the simple things that go wrong first...
    Well Naf, I might agree with you if we were talking about an older model car.

    Based on my experience however, the MAF and spark-related electrics on modern unmodified cars rarely malfunction before 50,000k. I have three cars in my driveway with more than 80k miles on each - none have had any MAF or spark-related electric issues. On a CTS-V a motor mount is statistically more likely to fail than the MAF or spark-related electrics. Additionally, checking the motor mounts, is starting with the simple since they are easy to check - they are either leaking or they ain't.

    Finally, the LS6 does have a normal intermittent "shimmer" at idle , which may be all that is going on here.

  9. #8
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    Re: Rough Idle Question

    Quote Originally Posted by darkman View Post
    Well Naf, I might agree with you if we were talking about an older model car.

    Based on my experience however, the MAF and spark-related electrics on modern unmodified cars rarely malfunction before 50,000k. I have three cars in my driveway with more than 80k miles on each - none have had any MAF or spark-related electric issues. On a CTS-V a motor mount is statistically more likely to fail than the MAF or spark-related electrics. Additionally, checking the motor mounts, is starting with the simple since they are easy to check - they are either leaking or they ain't.

    Finally, the LS6 does have a normal intermittent "shimmer" at idle , which may be all that is going on here.
    Darkman nails it again. An LS6 is a cammy motor- it's always going to have a little lope to it.
    Rest in Peace, J.D. (aka Dirt_Cheap_Fleetwood)

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    Re: Rough Idle Question

    It is simple to determine if it is a motor mount issue.

    When you turn the car off, does it shake for a quick second, almost like it's deiseling, or does it just immediately shut off. If it shuts right off, then no motor mount issues. If it feels like it's deiseling, then you have at least one shot motor mount. [Ask me how I know x 2]

    -Chris
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  11. #10
    sy1172 is offline Banned
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    Re: Rough Idle Question

    Emabarrasing isn't it. Cammy motor, sure but come on, the shake is totally not necessary. Have your motor mounts checked. I had a bad one recently and it caused a worse shake than normal.

    My other car has a 6.1 liter hemi at 420 hp and is Lexus smooth...go figure!

  12. #11
    Mystical_Ice's Avatar
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    Re: Rough Idle Question

    hmm... mine usually shakes the whole car for about a second before it dies.

    think that could be the motor mount? no other problems though during driving or anything

  13. #12
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    Re: Rough Idle Question

    Great info guys. I just got my car this week and I noticed the "little jiggle" at idle and the car does shake after I turn it off. I was going to post this same question tonight...thought it just may be a normal trait of the V. Man I have missed being on the forums especially where people actually know what they are talking about. Thanks again.

  14. #13
    CTSV_Rob's Avatar
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    Re: Rough Idle Question

    Quote Originally Posted by Naf View Post
    Hey,

    Ok you guys seem to always jump to the worse stuff before lookin at the obvious.

    You say you have 8500mi on the car, i would rule out almost all major components like motor mounts, they dont go bad that quickly.

    If possible check your MAF sensor, make sure its clean. From there check the inside of your intake manifold. There might just be a bit too much gunk in the intake, where when its strugglin with the A/c it effects your idle.

    I would then do a simple ignition check. Make sure the wires are fine, reading about the same amount of Ohms +/- 10-50 on stock is fine.

    Then check the plugs, you may have a bad one, check 7 & 8...They normally spoil first.

    If all that showes no sign of issues, then you think the motor mount, ot other hardware related issues. You know it may even be a bad o2 sensor. It is directly related to the engine function. You have to think from start to finish then consider surroundin hardware.

    I always start from the air inlet and work all the way to the exhaust. If i dont see or find any issues then i work to other related issues that may cause similar symptoms..

    Start simple then go complicated...You will find that 99% of the time its the simple things that go wrong first...
    I think this is a good write up Naf and it is thing's that should be checked.

    If you search back in threads there is a thread about PCV catch cans. The reason it needs it is because this is a high compression motor and some blow by is considered normal by our friends at GM.

    It is quite possible the rough idle is normal but it could also be something in the intake or a motor mount.

    If you want to ge this fixed (if it is a problem) you will need to trouble shoot yourself and then help the dealer with the problem. Seems rediculous but unless it's a hard failure they will quite often claim "this is normal operation" .

    Since the excessive oil in the intake bugs the shat out of me I am putting a catch can on my V.

    I realize I have a LS2 (and it's not a LS6) but I am happy with the slightly rough idle. Just reminds me that she want's to play once in a while.

    Who knows, maybe she just requires a little spirited driving to blow out some carbon build up.

    The car may not be carberated but it never hurts to start with the basics.

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    Re: Rough Idle Question

    Quote Originally Posted by ScottR View Post
    Great info guys. I just got my car this week and I noticed the "little jiggle" at idle and the car does shake after I turn it off. I was going to post this same question tonight...thought it just may be a normal trait of the V. Man I have missed being on the forums especially where people actually know what they are talking about. Thanks again.
    Great Forum and I'm glad I became a supporting member.

  16. #15
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    Re: Rough Idle Question

    Good point...def worth the $$$ from what I have seen, I'm in.

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