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2017 XT5 FWD
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Discussion Starter · #1 ·
Hey guys, I was trying to figure out if the shakiness/vibration I’m feeling while I’m in the driver seat is normal? It feels to me as if changing the spark plugs is needed but my Xt5 only has 46,000 miles on it.
The main thing I’m wondering is since it is pre-owned and was sitting for a while, would that make the spark plugs wear out sooner than normal?
 

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Are you sure it's not the Safety Alert seat? On a somewhat more serious note, if you're concerned about carbon buildup, run a tank or 2 of premium Top Tier fuel through and see if that helps.
 

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2018 Cadillac XT5 Luxury
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It is not normal for it to do that. Is it still under warranty, if so I would take it to a dealer. One thing you can try is take it on a hard run on the highway after properly warming it up first and see if the issue persists. A hard run will clear some of the carbon deposits which may have built up.
 

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Discussion Starter · #4 ·
Are you sure it's not the Safety Alert seat? On a somewhat more serious note, if you're concerned about carbon buildup, run a tank or 2 of premium Top Tier fuel through and see if that helps.
Haha no definitely not the safety alert! But I normally run Shell 87, but I will go for the premium for the next few to see any change. Thanks!

It is not normal for it to do that. Is it still under warranty, if so I would take it to a dealer. One thing you can try is take it on a hard run on the highway after properly warming it up first and see if the issue persists. A hard run will clear some of the carbon deposits which may have built up.
I actually haven’t tried to go for a hard run at all in the vehicle. I have had some experience with law enforcement and over here in Gretna, LA they are always looking to cause trouble. But I will have to go ahead and do that to see if it helps. Thanks!
 

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2020 XT5, AWD Platinum, Garnet Metallic, 20" Ultra-Bright
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Shell 87 and 91(or 93) depending on location are both Top Tier. When a gasoline brand is advertised as Top Tier, all pumps for with that brand must have the same minimum cleaner blend. Shell does advertise their V-Power to have more than the other grades. A couple of tanks will not make a noticeable improvement, since you regularly use Top Tier.

Will the warranty you received with your CPO cover a diagnostic visit?
 

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2020 XT5 Platinum in Red Horizon Tintcoat and Maple Sugar interior
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Running a few tanks of 93 octane Premium to "clean out your engine" is a waste of money and does nothing. The higher octane rating is not a cleaner. It only serves to help eliminate any pinging or knocking. If your car is exhibiting neither of those then 87 octane is all you need. Also - a car sitting for a while will not wear out your spark plugs. What may help however, if you are a little bit handy, is getting a can of Seafoam and spraying it directly into the intake while the engine is running which will help in cleaning away any carbon buildup.
 

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Discussion Starter · #7 ·
Running a few tanks of 93 octane Premium to "clean out your engine" is a waste of money and does nothing. The higher octane rating is not a cleaner. It only serves to help eliminate any pinging or knocking. If your car is exhibiting neither of those then 87 octane is all you need. Also - a car sitting for a while will not wear out your spark plugs. What may help however, if you are a little bit handy, is getting a can of Seafoam and spraying it directly into the intake while the engine is running which will help in cleaning away any carbon buildup.
That’s why I asked, because I haven’t heard of a car sitting up causing spark plugs to need replacement sooner than normal.
I do appreciate it, and as for the seafoam..would you not recommend the CRC cleaner instead of seafoam? I have always heard seafoam wasn’t good for your vehicle but I’d like to hear your opinion of it so I can make my own decision. I definitely appreciate everyone’s knowledge. Yes I am handy enough to disassemble the intake to spray the seafoam, my question about that is, is it necessary to replace the gasket ?
 

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2020 XT5 Platinum in Red Horizon Tintcoat and Maple Sugar interior
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That’s why I asked, because I haven’t heard of a car sitting up causing spark plugs to need replacement sooner than normal.
I do appreciate it, and as for the seafoam..would you not recommend the CRC cleaner instead of seafoam? I have always heard seafoam wasn’t good for your vehicle but I’d like to hear your opinion of it so I can make my own decision. I definitely appreciate everyone’s knowledge. Yes I am handy enough to disassemble the intake to spray the seafoam, my question about that is, is it necessary to replace the gasket ?
The CRC may be ok. Personally I like the Seafoam spray myself and have done it on many cars with good results. It's really the best way to clean the top end. YouTube has many videos on how to use the Seafoam for this purpose. Just search "Seafoam intake cleaning". No gaskets should need to be replaced.
 

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2018 Cadillac XT5 Platinum AWD
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I don't think an engine of this new generation with so few km has such a problem with carbon that it vibrates.
But I like to be surprised.
 

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2020 XT5, AWD Platinum, Garnet Metallic, 20" Ultra-Bright
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Perhaps you need to clean the throttle body. 46K is enough mileage to create a dirty throttle plate/venturi.

Sounds like you are handy enough to clean it yourself using Throttle Body Cleaner (do not use carburetor or brake cleaner. They are too harsh). No gasket required...loosen the worm drive clamp and pull the intake tubing off the throttle body. Push the throttle open with your finger and spray the cleaner on a cotton cloth and rub the black residue off the throttle bore and throttle plate. You can use a tooth brush to reach inside if you wish. Just don't use it to brush your teeth after use with the throttle body cleaner.
 

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Discussion Starter · #11 ·
The CRC may be ok. Personally I like the Seafoam spray myself and have done it on many cars with good results. It's really the best way to clean the top end. YouTube has many videos on how to use the Seafoam for this purpose. Just search "Seafoam intake cleaning". No gaskets should need to be replaced.
Okay great! I was just researching and it says to replace gaskets for intake and throttle body after taking them apart but in my own opinion, I didn’t think it was necessary unless there was a problem with the gasket. Thanks!!

Perhaps you need to clean the throttle body. 46K is enough mileage to create a dirty throttle plate/venturi.

Sounds like you are handy enough to clean it yourself using Throttle Body Cleaner (do not use carburetor or brake cleaner. They are too harsh). No gasket required...loosen the worm drive clamp and pull the intake tubing off the throttle body. Push the throttle open with your finger and spray the cleaner on a cotton cloth and rub the black residue off the throttle bore and throttle plate. You can use a tooth brush to reach inside if you wish. Just don't use it to brush your teeth after use with the throttle body cleaner.
I have taken it apart and it was slightly dirty but I did not use any cleaner. I simply wiped it with a microfiber cloth (I hope that isn’t a problem) and I got a good bit of the residue off. I will probably end up using some cleaner. At this point, It may just all be in my head! I’m going to get the wife to jump in the driver seat, she will be able to tell me if she thinks it’s rough.
I don't think an engine of this new generation with so few km has such a problem with carbon that it vibrates.
But I like to be surprised.
I also agree, and the reason I ask this forum is because y’all are more helpful than most!
 

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I have taken it apart and it was slightly dirty but I did not use any cleaner. I simply wiped it with a microfiber cloth (I hope that isn’t a problem) and I got a good bit of the residue off. I will probably end up using some cleaner. At this point, It may just all be in my head! I’m going to get the wife to jump in the driver seat, she will be able to tell me if she thinks it’s rough.
A dry cloth will not clean as well as the throttle body cleaner. There are passages for idle air that are quite likely restricted by the residue you saw. While you have the air intake ducts apart, inspect the MAF (Mass Air Flow Sensor) for visible dirt and spray with Mass Air Flow Cleaner for a complete induction duct cleaning. Don't use the Throttle Body Cleaner on the MAF. Purchase the Mass Air Flow Cleaner for that purpose. The MAF is very sensitive.
 

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@Codyf9492 ...while working on your intake duct work, how long ago was your air filter changed? If it has been a while, a new one is not very expensive.
 

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2018 Cadillac XT5, 2013 Toyota Avalon Hybrid Limited
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That’s why I asked, because I haven’t heard of a car sitting up causing spark plugs to need replacement sooner than normal.
I do appreciate it, and as for the seafoam..would you not recommend the CRC cleaner instead of seafoam? I have always heard seafoam wasn’t good for your vehicle but I’d like to hear your opinion of it so I can make my own decision. I definitely appreciate everyone’s knowledge. Yes I am handy enough to disassemble the intake to spray the seafoam, my question about that is, is it necessary to replace the gasket ?
These GDI engines are prone to carbon build-up on the intake valves and induction system. Top tier or premium gas and fuel system cleaners put in the gas tank will not clean it like they do on port injection engines so you have to do, or have done, an induction cleaning service. If you are experiencing a problem related to carbon build-up you will need a stronger product than Seafoam or CRC. The best is BG. I did the BG service myself at 17,000 miles and noticed a huge improvement. See post # 34 below for the equipment and materials I used. Alternatively, you could have it done for about $150.00.

(4) Valve cleaning? | Page 2 | Cadillac Owners Forum (cadillacforums.com)
 

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2018 Cadillac XT5 Platinum AWD
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Interesting facts about our engine:


  • Two-stage PCV system: this revolutionary system maintains low oil consumption, featuring a pre-separator between the block and the engine’s rear cover and a high-efficiency separator in the center of the block’s “V”.
 

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These GDI engines are prone to carbon build-up on the intake valves and induction system.
The LGX/LGZ engines with their advanced PCV systems have not exhibited carbon build-up issues. The LGZ is used in the mid-sized trucks with different oil filter placement and longitudinal placement. All of the hype about carbon buildup used pictures of valves from European DI engines, but when challenged for proof of carbon buildup in GM DI engines, the catch-can vendors failed to produce any proof...just lots of words and recycled pictures.

I am not saying it cannot happen, but when full synthetic oil and Top-Tier gasoline is used in GM engines since 2014, evidence of carbon build-up cannot be found.
 

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Carbon build-up on GDI engines is not so much about the PCV system. Tiny amounts of oil pass through the seals on the valve stems. This is what creates the carbon buildup. Of course the PCV system is important in not allowing pressure to buildup in the oil passageways so it's not forced through the seals, but some will pass anyhow. The heat from the exhaust will keep those valves cleaner, but the intake side is where deposits are more often found. Good oil can prevent this. Several oil makers have created formulas specifically to help prevent this. Still, it will likely happen over time, but 45K miles seems too soon.
 

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How is exhaust gas recirculation implemented on the XT5? The engine has integrated the manifold in the cylinder head.
 

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Carbon build up happens more on cars that never see highway use and only just short trips to the corner store. So the mileage can be quite low due to short trips, but the engine never warms to the point where it burns off the carbon.
 

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Discussion Starter · #20 ·
Carbon build up happens more on cars that never see highway use and only just short trips to the corner store. So the mileage can be quite low due to short trips, but the engine never warms to the point where it burns off the carbon.
This is a possibility. I don’t drive very long as my job is about 15 minutes away and the max speed I travel is 40 MAYBE 45 miles an hour. Every now and then I will go on the highway at about 65 MPH but for a short period of time (5 minutes max).

@Codyf9492 ...while working on your intake duct work, how long ago was your air filter changed? If it has been a while, a new one is not very expensive.
Yes my air filter is close to being time to replacement. I am just waiting for my appointment at the dealer to let them replace it under my premium maintenance warranty (which I believe is free). I have blown the dust particles out with an air hose at my previous job (oil change shop)
 
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