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Had the car out yesterday for a short drive. On the way back home, I noticed a vibration at idle. Doesn't seem to be there when driving, just idling (stopped). Not like the whole car shakes, but it is definitely noticeable. I won't know till the next time I drive it if it's still there or not. Anyway, anyone else experienced this? I found that there are lots of posts about vibration in other model forums but didn't see anything under XTS.
 

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Had the car out yesterday for a short drive. On the way back home, I noticed a vibration at idle. Doesn't seem to be there when driving, just idling (stopped). Not like the whole car shakes, but it is definitely noticeable. I won't know till the next time I drive it if it's still there or not. Anyway, anyone else experienced this? I found that there are lots of posts about vibration in other model forums but didn't see anything under XTS.
I was in a 2016 CTS 2.0T and that thing had a very rough idle for a brand new car. Granted it had the auto start/stop so when it kicked back on it idled really rough. My XTS is so smooth I can't really tell its running.
 

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Mine initially was the same...couldn't even tell it was running at idle. Was out in it again yesterday and the rough idle is still there. As soon as you give it any gas, it stops...so it's almost like the RPM's are too low at idle. If it keeps up, I guess a trip to the dealer is in order.
 

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While not as smooth as my 2013 Verano turbo-4, my VSport was getting a noticeable roughness to it on my 8 mile, half highway commute. After this holiday's 450 miles of highway driving the roughness is not noticeable now. Just needed a good cleaningbout on the highway?
 

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I know it’s a very old thread, but wondering if anything was discovered that was causing the vibration? My new 2018 xts awd is doing the same
 

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For a few months now, I'll come to a stop in drive, car idling smooth as silk, then a slight vibration starts. Not every time. Feel it in the steering wheel, sometimes the seat and shifter also. Disappears as soon as I start moving. 35k easy miles.
Not bad enough to make me want to investigate further, yet. Since it's intermittent, I'm guessing maybe some emission control thing. Wife's Impala has had a slight, same vibe since new, same engine LFX.
 

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Our XTS only has 9600 miles with the same rough idle. Our 2009 CTS has 81000 miles and you can’t even feel it idle. I’ll Be taking it in for an oil change in a couple of weeks and have them check it out. Seems to be a common issue. Im surprised nobody has gotten an answer to it.
 

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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.
 

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If the vibration is at idle (in gear), stationary and goes away if you put the tranny in neutral, it may be a motor or transmission mount. It may not be, but something to consider.
 

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Kevinst has his checked out. The dealer checked the motor mounts and exhaust pipes. Did not help. You can check his post regarding a steering wheel vibration when stopped. I just went out to warm mine up and charge up the battery. After it was warmed up I put it drive and the vibration started within a few seconds.
 

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Drove car home today. Dealer can’t find a problem. Still has a rough idle.������
 

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Was at the dealer again today. I brought up the idle issue again. This time I was told that they have had numerous complaints about this. It only seems to be exclusive to the XTS. They think it might be caused by the winter fuel mix. Mine had the problem last winter, went away in the summer and came back again this winter. Maybe that’s what causes it.
 

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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.
 

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The dealer changed my oil and installed a new air filter at the time I brought up the idle issue. Neither made a difference. That was back in February. I have noticed a big improvement with the warmer weather.
 

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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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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-engines/lfx/#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
 

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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.
 

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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.
 
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