Vibrations at idle

[SpThomass]

06’ Yukon Denali XL, 6.0L, AWD

I’m just curious if anyone knows why it does this, or if anyone else experiences this.
I don’t think it’s a very serious issue, and it could very well be the rubber engine mounts are on their way out. It just vibrates or like shutters I would say at idle. It’s not a very aggressive vibrating either just enough to notice and happens intermittently.
For some background information; it doesn’t idle rough. I use 89 octane gas and regularly use an octane additive, but this was present before I started using that. I have a performance air filter and a brand new MAF. I use performance coolant and additives and installed a brand new radiator as well. The engine itself is very clean, I use royal purple, so it’s maintained nicely.

This is a long post, sorry, but could it be the belt maybe? Could it be an air manifold leak? Again it’s not a very serious thing, just annoying.

thanks in advance

 

[OR VietVet]

How old are the tune related components? Plugs, wires, fuel filter....miles on the engine? Any recent engine related work? Did you check for a vacuum leak? Have you tried premium fuel to see what happens? What brand of fuel do you use?

 

[SpThomass]

How old are the tune related components? Plugs, wires, fuel filter....miles on the engine? Any recent engine related work? Did you check for a vacuum leak? Have you tried premium fuel to see what happens? What brand of fuel do you use?

I guess I should have said that originally, my bad. The Plugs are brand new NGK, and the ignition wires were replaced as well, Duralast gold. I haven’t done anything with the fuel filter, I haven’t noticed any problems with it as of yet. The odometer is just why if 211k, and as for the vacuum leak, I sprayed some carburetor cleaner towards the intake gasket and it didn’t show any signs of a vacuum leak, but maybe I could
Give it another try. As for the premium gas, I have tried it, haven’t really noticed a difference with the vibrations, and I’m not sure the brand of gas, I just use the gas station on military installations.

 

[Fless]

First couple minutes of this video shows a way to check that motor mount.

 

[OR VietVet]

Even without likely knowing the age of the fuel filter and the miles on it, you should change it, NOW. It may not fix your vibes but it will help save the fuel pump. Fuel filters get clogged after a certain amount of mileage and that clog makes the fuel pump work harder to maintain fuel pressure to the fuel injectors. You are overworking your fuel pump. Don't even need carb cleaner to spray around the intake and other vacuum items. Spray water works just as good. Like out of a plant sprayer. I forgot to ask, any CEL? Codes?

To check the motor mounts, have a trusted friend get behind the wheel and while you watch the engine movement, have your friend put in reverse and drive and when in those gears, have the engine at idle but have your friend quickly "goose" the throttle and see how far the engine jumps up. It will torque one way or the other depending on the gear you are in. Some movement is acceptable but if you see the engine jump and not just pull against the rubber mount, then you have a bad motor mount(s). You are looking for a "jump" effect from the engine.

The video above was posted during me typing this.


https://www.rockauto.com/en/moreinfo.php?pk=7203312&cc=1432471&jsn=2204

 

[22YukonDenali22]

My engine vibrates a bit at idle and in park. I've done quite a bit of investigating, and have done complete tune ups and changed the motor mounts. It still vibrates a bit. Engine idle is steady 500-550 rpm. I think it's normal, at this point.

 

[OR VietVet]

My engine vibrates a bit at idle and in park. I've done quite a bit of investigating, and have done complete tune ups and changed the motor mounts. It still vibrates a bit. Engine idle is steady 500-550 rpm. I think it's normal, at this point.

Have you done a compression test? You are not saying what year and engine and mileage.

 

[22YukonDenali22]

Have you done a compression test? You are not saying what year and engine and mileage.

2008 GMC Yukon Denali, 6.2 L, 95k miles. I've not done a compression test. The vehicle runs awesomely, besides that slight engine vibration at idle/park. I decided to stop worrying so much about it; it has never given me actual driveability problems. I only posted my response to support the original poster that it might be normal. There are tons of Silverado/Sierra/Tahoe/Yukon owners in the 1999-2013 that have reported similar vibrations, even when brand new.

 

[OR VietVet]

There have been some other posts from members with the 6.2 engine that say that engine vibration seems to be normal.

 

[the_tool_man]

I's be surprised if it was a motor mount. I just replaced the driver side motor mount on my 2012 Denali, which should be the same as yours. It was ripped almost completely apart. I noticed no engine vibration at all, at idle. I could tell the mount was broken because there was a pronounced "clunk" under acceleration as the metal parts of the mount would hit each other as the engine torqued over.

When I replaced the mount with a solid rubber H3 one, I DID notice a vibration at idle that I hadn't noticed before. So I think a broken mount would tend to HIDE vibration, not cause it. Easy enough to check, I suppose.

In my experience, one of the more common causes of rough idle is dirty fuel injectors. Run some Lucas injector cleaner in the fuel for several fill-ups, and see if this helps.

Other things it might be:

Sticking throttle body, dirty MAF sensor, lazy O2 sensors, or a clogged fuel filter. The coils could be getting weak. But if there is a misfire, the ECU should detect it and throw a code. If you do get a misfire code, and it's tied to a particular cylinder, you can swap coils to test whether it's that, or a plug or wire.