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Cadillac XTS Forum Discussion, Vibration at idle in Current Cadillac Vehicle Discussion; Originally Posted by rockit I changed the oil a few days ago and noticed that the idle in gear seems ...
  1. #16
    ricktherealtor1 is offline Cadillac Owners Member
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    Re: Vibration at idle

    Quote Originally Posted by rockit View Post
    I changed the oil a few days ago and noticed that the idle in gear seems much smoother. I have read that the Variable Valve Timing is controlled by oil flow and can be sensitive to viscosity. So maybe this is related. The Valvolene full syn oil had 4k mi. and 10 months on it. Replaced with Mobil 1. Car has 35k mi.
    See my post #6 in this thread.
    I don't believe our XTS's have VVT. My Vsport doesn't.

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  3. #17
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    Re: Vibration at idle

    From GM Authority: "Variable Valve Timing: variable valve timing (VVT), or cam phasing, helps the LFX deliver optimal performance and efficiency, and reduced emissions. It allows linear delivery of torque, with near-peak levels over a broad rpm range, and high specific output (horsepower per liter of displacement) without sacrificing overall engine response, or driveability. The system changes valve timing on the fly, maximizing engine performance for a variety of operating conditions. At idle, for example, the cam is at the full advanced position, enabling exceptionally smooth idle quality. Under other operating demands, cam phasing adjusts to deliver optimal valve timing for performance, driveability and fuel economy. At high rpm it might retard timing to maximize airflow through the engine and increase horsepower. At low rpm it can advance timing to increase torque. Under light-load driving it can retard timing at all engine speeds to improve fuel economy.

    Read more: http://gmauthority.com/blog/gm/gm-en...#ixzz5m2m922mN

    LF3 from Wikipedia:
    The 3.6 L twin-turbocharged version for the 2014 Cadillac CTS and 2014 Cadillac XTS has been announced at the 2013 NYAS.[15]
    In essence, the twin-turbo 3.6L V6 is the force-inducted variant of the popular LFX V6 currently found in the Cadillac ATS, XTS, and SRX, among many other GM models, with several important upgrades, including:
    Continuously variable valve timing

  4. #18
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    Re: Vibration at idle

    The engine cover also has a VVT Direct Injection designation.
    rockit likes this.

  5. #19
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    Lightbulb Re: Vibration at idle

    I believe the problem is the radiator's electric cooling fans being out of balance. If the problem's been since new the fans were not balanced properly, if over time then one or both fans may have throw a clip on weight (that's how they're balanced). I've been renting XTS's since they came out, sometimes for mo's at a time, had two 19's this year alone, the first had 14000 miles and there was 0 vibration at idle, the second also a 19 with 9k has the vibration. I always associated it with the engine or driveline but I can say with reasonable confidence the cooling fans are the issue. Ask your service dept to speak with its shop foreman to disconnect the fan's power and see if issue goes away...bet it fixes the problem. Let me know.

  6. #20
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    Re: Vibration at idle

    Quote Originally Posted by GFK View Post
    At times, I wonder if it is a carbon built up issue. I try and use gas with no ethanol and/or mid-grade. I look for top-tier gas. It seems to work with the rest of my vehicles. The XTS, I still notice a rough idle at times. I may try and use ethanol free gas only. But, it is only offered at limited stations in my area that are top-tier. In particular, it is only one within a 40 mile radius of were I live.
    The vibration issue is almost certainly due to a carbon buildup on the intake valves, which all direct injection engines are known for. It's a common well documented problem. Using a Top Tier gas will do nothing to remedy the problem either, as the fuel is injected directly into the cylinders, bypassing the valves, as opposed to a port injected engine, where the fuel is sprayed across the valves, thus cleaning them. Adding a fuel cleaner additive to the gas tank will do nothing either. There are several easy methods to clean the valves yourself, using SeaFoam, etc. I've done it on my XTS and it works fine.

  7. #21
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    Re: Vibration at idle

    Quote Originally Posted by sonny3621 View Post
    The vibration issue is almost certainly due to a carbon buildup on the intake valves, which all direct injection engines are known for. It's a common well documented problem. Using a Top Tier gas will do nothing to remedy the problem either, as the fuel is injected directly into the cylinders, bypassing the valves, as opposed to a port injected engine, where the fuel is sprayed across the valves, thus cleaning them. Adding a fuel cleaner additive to the gas tank will do nothing either. There are several easy methods to clean the valves yourself, using SeaFoam, etc. I've done it on my XTS and it works fine.
    I beg to differ. We have had the vibration at idle in several brand new XTS's we've rented long term for travel over the years all with +/- 10-20 miles on the odo, and we just had another rental XTS with 14k and 0 vibration (no doubt as a rental the cheapest gas was used). Now we have another 19 XTS with 9k which has the vibration. As I posted above I believe it's the cooling fans not being properly balanced or perhaps the assembly not secured properly by the rubber grommets which are there to reduce any vibration the high speed fans cause (which can be significant if not balanced properly), or the fans may be out of synchronization with each other.

  8. #22
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    Re: Vibration at idle

    Mine only vibrates in the winter. Summer is smooth.

  9. #23
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    Re: Vibration at idle

    Fans run all seasons

  10. #24
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    Re: Vibration at idle

    So why is there no vibration in the summer?

  11. #25
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    Re: Vibration at idle

    Have no idea why yours only vibrates in the winter, but the vibration in ours only comes on when the cooling fans go into a higher speed mode, within a minute of the fans slowing back down the vibration is gone until they go back into high speed mode. It appears the fans are out of synch with each other...If you've ever piloted a twin engine plane or boat it's the same type of resonance. If you want to be sure you can unplug the cooling fans connections and see if it goes away...it does on ours. This vibration has been plaguing many new XTS's since they came out.

  12. #26
    Kevinst is offline Cadillac Owners Member
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    Re: Vibration at idle

    Same with my 2018 xts awd... see my earlier posts about vibration at idle... now that it’s warm out no vibration at all and nothing has changed, not even the oil. (Only have 3300 miles on it since November).

    Only thing I can think is winter gas versus summer gas mixtures...

  13. #27
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    Re: Vibration at idle

    The winter mix was something the service dept mentioned to me. They said only XTS owners are complaining about the problem.

  14. #28
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    Re: Vibration at idle

    I'm starting to think my April oil change and idle improvement coincidently coincided with the seasonal fuel changeover. Car still idling smooth as silk. We'll see what happens in the fall.

  15. #29
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    Re: Vibration at idle

    Quote Originally Posted by sonny3621 View Post
    The vibration issue is almost certainly due to a carbon buildup on the intake valves, which all direct injection engines are known for. It's a common well documented problem. Using a Top Tier gas will do nothing to remedy the problem either, as the fuel is injected directly into the cylinders, bypassing the valves, as opposed to a port injected engine, where the fuel is sprayed across the valves, thus cleaning them. Adding a fuel cleaner additive to the gas tank will do nothing either. There are several easy methods to clean the valves yourself, using SeaFoam, etc. I've done it on my XTS and it works fine.
    I just cleaned my valves, I don't believe it's been done since new (I bought it used) and it has 109,000 miles on it. I used a can of the CRC GDI cleaner first and then the next day used the Seafoam cleaner and lube. It seems to have cleared up the really low idle the makes the car shake but I think it's time to do the spark plugs as I can't see in the history of the car of it being done.

  16. #30
    Cadjiek is offline Cadillac Owners Enthusiast
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    Re: Vibration at idle

    At 10,000 miles I don’t think I would have that much carbon buildup to create my problem. Besides, it idles smooth in the summer and rough in the winter. Weird.

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