rough idle/vibration

[mjwills]

Hi all - I'm new to the forum and appreciate any help. I just came out of a 2005 ESV into a 2011 Yukon XL 2500. Even though they both had the 6.0L - are there differences? I know the tranny is different and I am still learning shift patterns, etc.

Upon start up it sticks around 1200 and after a minute will creep down to 600. Is that normal?

Sometimes at lights or in park there is a rough idle - bounces up or down 50-100rpm. I cleaned the throttle body and put in a K&N filter and waiting to see if that helped out enough. No engine lights are on so I assume it is not miss firing. When it is in park and doing this I opened the hood and the trans dip stick was shaking really bad from the vibration.

Any other things to look at?

Thanks!

 

[mentalattica]

I'm not as knowledgeable as most of the folks on here but as far as when you're starting the engine that sounds normal to me. All of my vehicles do that.

As far as the rough idle how many miles are on it? Have you taken a look at the plugs? If not I'd pull a couple and see what they look like, also check the wires. I've had a few vehicles that were missing and not throwing any codes, in fact my Saturn is currently doing that.

If the plugs and wires look good maybe there's a vacuum leak somewhere? You can also try running some Seafoam (or something of the likes) through it too.

Maybe someone will chime in with better info, but the plugs and wires is where I'd start.

 

[mjwills]

Thanks for the response. There is 80k on it.

 

[CrashTestDummy]

The behavior your seeing at startup is normal. The idle hunting like that is not. You may want to have a dealer check that out, there may be a sensor that's not working correctly, or the throttle positioning sensor (TPS) may be out of adjustment.

 

[mjwills]

Taking it to dealer Monday. There are really 2 vibrations going on. One at idle where it's fine and then you hear a click and then a surge comes through column, dash and seat. The other is one that I feel only around 1800 RPM - in the feet and column. This may be more of a droan?? I can drive through it, but after every shift it goes back to that point and at around 70mph its at 1800.

Do engine/trans mounts go bad?

 

[GM Customer Service]

Hello mjwills,

Our apologies to hear of the concerns you are experiencing with your 2011 GMC Yukon. We understand you'll be taking it in to the dealership on Monday, please keep us updated on your visit!

Regards,

Andraya
GM Customer Care

 

[rockenthebowtie]

Is it with the AC on only or on or off it kinda sounds what your describing like the AC compressor engaging but thats not normal you may have a AC COMPRESSOR starting to fail and or seize up causing the idle drop and at 1800 rpm at 70 mph

 

[mjwills]

Hi all - well no luck and its been to 3 dealers. They see it and feel it but are stumped on a fix. One dealer put a dampner behind the right side cat and the other put a new clamp on the exhaust and realigned it. Since there are no codes they keep thinking it is in the exhaust. Both say it could be a engine/trans mount but not 100% confident. I'm at a loss and its frustrating that the dealer can't solve it. Thoughts on next steps?

 

[mjwills]

Talked more with dealer. They said if it were them, a new exhaust is the fix. Would a cat back system work? Any other thoughts?

 

[992dr]

What's amazing to me is that these so-called certified technicians can't do there jobs.
Isn't diagnosing problems a part of there cert? And yet no one can find the problem. I feel your pain Mark. I've been going through some very similar issue myself.

You CAN have a misfire without throwing any codes. In fact you can have multiple misfires. That is more than likely your issue with the rough idle. This is my issue.

As silly as it sounds, yes motor and trans mounts do fail and it seems to be more common than not.

Check your u-joints and yoke to.

edit I find it very hard time believe its the exhaust. Check your u-joints and yoke.

 

[CAgilbuena]

Any luck? i've got the same issue at idle. I'm beginning to think it's a fouled plug. Got some hesitation sputtering on an uphill climb. Going to inspect the plugs in the morning.

 

[Lancaster]

Thanks for the response. There is 80k on it.

Thought 1: My experience is that 80k is too much for these plugs/wires. I did mine at 105k. The origional plugs were well worn - the only electrode remnants being rounded little nubs. The wires were brittle.

Thought 2: night and day difference when MAF and TB are cleaned.

Thought 3: please discard the k&n. My experience is that they wreak havoc on intake electronics ultimately costing you more in diagnosis fees than OE filters and the hp gain, especially on an SUV, are imperceptible.

 

[992dr]

Any updates?

OE plugs typically last 100k miles. I'd read them before replacing them, same goes for the wires.

K&N gets a bad rep because of the miss use of there products, basically over oiling them. They make great products that last as long as you maintain them properly. This miss use also effects the MAF as well as the TB. You do not use liberally, use sparingly and give it an adequate amount of time for the oils to settle into the filter.

It wouldn't hurt to clean your MAF. Be careful when cleaning your TB as its drive by wire.

 

[mjwills]

I took it to an independent shop. They replaced the exhaust hangers and the vibration is 90% gone. - night and day difference. I guess the exhaust mounts were all worn. Not to sure why the dealer didn't replace that when they had the exhaust off. Now I still feel something, but was in a friends Denali today and feel the same thing. They confirmed that engine and trans mounts were fine. My initial question is what is causing the exhaust to vibrate that much to begin with. They think it is originating from the trans (see below).

I still think there is something loading the engine, but this shop went through everything and it all checked out from a mechanical standpoint.

I still have a droan at 1800 RPM. When putting scopes on it, there is excessive noise coming from the middle area of the trans. How do I prove that to a dealer?

 

[Lancaster]

I took it to an independent shop. They replaced the exhaust hangers and the vibration is 90% gone. - night and day difference. I guess the exhaust mounts were all worn. Not to sure why the dealer didn't replace that when they had the exhaust off. Now I still feel something, but was in a friends Denali today and feel the same thing. They confirmed that engine and trans mounts were fine. My initial question is what is causing the exhaust to vibrate that much to begin with. They think it is originating from the trans (see below).

I still think there is something loading the engine, but this shop went through everything and it all checked out from a mechanical standpoint.

I still have a droan at 1800 RPM. When putting scopes on it, there is excessive noise coming from the middle area of the trans. How do I prove that to a dealer?

Set the dealer's expectations by requesting a test drive with you as the driver. Fill them in on the history so they know what is going on. They never look at the history. If you are lucky enough to get a good tech or service manager, you should be in good shape.

 

[YukonXLPerk]

Motor mounts?
A broken motor mount will cause the shaking you are experiencing.

The idle moving up and down a little is normal. The computer will increase the rpm slightly so that it will not stall when your accessories place a load on the system.
Search the forum about this problem. Some of us have sworn to have found a fix for this.

 

[ccapehartusarmyINF.(ret)]

usually to check the the motor mounts have someone in the drivers seat put in gear while holding the breaks giving it a little gas while you watch with the hood up to see if the engine moves excessivly make sure you dont stand infront though lol

your definatly correct on the misfire codes in fact fords actually have to have so many misfires continuously right in a row before the PCM throws a code
im tottally with you on your gripe with the so called certified technicians
im actually curious what makes them certified because i spent almost two years at UTI
in there auto\diesel and ford fact program and i even found some time in there to get a couple asc certs knocked out and i dont refer to myself as a certified technician
is there some special GM certification corse?

 

[harveje]

We've changed plugs, wires, injectors, cleaned the TB, MAF, seafoamed, etc..etc... still have a miss. I've put a tech 2 and no codes, mis fires, etc... still chasing the rabbit..

 

[mjwills]

Bringing this up again as I am still chasing it down. I have new motor and trans mounts and front hub bearing going in this week. If this doesn't solve it I am at a loss.

Jumping ahead, but the vibration goes away if I put it in neutral and if in gear and brake torque it I can get the sound/vibration around 1800 RPM. If the mounts do not fix this, could there be an issue in the torque convertor? Is that in motion once the car is in gear? Do trans/driveline issues through codes? (I have not seen any).