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Discussion Starter #1
I own a 08 GMC, and for the last year I've had a strong exhaust smell in the truck when the truck is sitting at idle. Usually when I've pulled up to a stop light, or after the truck has warmed up. I've taken it to multiple dealers and they can't find anything wrong with the truck.
My fuel mileage has been around 13 mpg.
Have any of you guys had this problem?

PDQUICK
 

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i swear that there was a thing on this from the dealership something with V band clamp or something on downpipe??
 

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Slave to the Interwebs
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It is on the downpipe. Check the v band clamp.

This was posted by a member who is a tech at a large GM Dealership. His name will remain anonymous. As he almost lost his job because of the post

To start I am a technician
We are the states largest volume dealership in the past few months.

I have heard lots of people complaining about their lmms and fuel mileage. Many more people have complained that after they got the ecm reflashed their mileage went way down.

As far as the regeneration goes I wanted to get some things straight. Things that I never new about the regeneration process.

The MAXIMUM amount of fuel that regeneration uses is 3 gallons per event. NOT 6 Gallons like some have stated.

The regeneration no matter what you tow or how you drive your truck on average comes on every 360-400 miles. The dpf soot is still calculated by the ecm, and how much fuel is used, how long you idle the engine all determines the actual regen events. Their is no warning that your truck is going into regeneration unless it hasn’t been able to meet the regeneration requirements.
(I.E) Your not driving fast enough 30mph to meet the criteria.
If you see a message in your DIC "CLEAN EXHAUST FILTER SEE OWNERS MANUAL NOW" and you don’t meet the requirements to make the truck go into regeneration. It then goes into limp mode. Limp mode is 2nd gear and 30mph

Our technical director right now is driving a 08 lmm with the ecm reflashed. The average fuel mile NOT towing anything is between 15.0-17.1 This is based on daily driving the min & max he has hand calculated. He has approximately 7,800 on the truck and mostly freeway driving.

Now to the point of this post. After talking with a knowledgeable source, he has seen MANY lmms customers that are complaining about horrible mpg. The fix in 95% of the cases is the turbo outlet pipe/down pipe. Their is a bulletin on " Diesel smell on regenerations " What hank told me today is gm has found the turbo outlet pipe or down pipe is leaking right off the back of the turbo due to a flaw in down pipe production. This is causing an estimated 2 mpg loss in fuel mileage. Their is only 2 ways to see if its leaking, remove the turbo shield and look for black soot around the band clamp at the turbo down pipe. Or gm has an exhaust pressurizing tool that puts pressure into the exhaust system checking for leaks. I hope this helps anybody with an lmm motor. If you take your truck to the dealer just tell them that you smell diesel in the cab of the truck mostly during regeneration. That should trigger the tech to look for this bulletin. It DOESNT SAY anywhere in the bulleting that is tied to low fuel mileage. So DONT go in their complaing about that.

TAKE AN ANGLED MIRROR, PUT IT ON THE BACK SIDE OF THE TURBO SHEILD AND LOOK FOR BLACK EXHAUST SOOT AROUND WHERE THE DOWNPIPE COMES OUT OF THE TURBO. IF YOU SEE SOOT, TAKE IT TO THE DEALER. THEIR SHOULD BE NONE
 

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Go into the Dealer with this number: PIP4360

If you do not have the number, they can not seem to find the bulletin/PIP.

Johnasara is right.
 

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oldschool
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I think this is a common thing
I took my stock down pipe out to replace it with an aftermarket one, the stocker had black soot on the outside of it. Truck had 30k on it. Didnt really smell it unless it was in regen and not moving
 

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Thanks Johnasara, I'll be checking the pipe on mine too. I've been smelling unfiltered diesel exhaust during regens while parked.
This reflash that apparently drops the mpg, is that a related service they do to the leaking turbo pipe??

I just re-read your post, it looks like you say the relation of the reflash and the mpg drop is only coincidental, is that correct?
 

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subscribed, mine is doing it really bad and I have to roll my windows down now..it didn't do it until I put the aftermarket DP on..
 

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Backwoods Outlaw
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I too have noticed this smell. Im will be taking my truck in within a week or so to have some mods done. If I get a new exhaust and DP will it clear the problem up?
Thanks in advance>

RD
 

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goplay,

I just saw this thread and watched your video. Is that a CO detector?

Here's my story. I have an '08 with 29,500 miles and have been getting a very noticeable exhaust smell in the cab on regen for some time. I'm around diesels all the time, so its not a big deal, or at least hasn't jumped high on the priority list for me.

A couple of months ago, I had been driving for about 2 hours in the truck coming back home on a short trip. Later that day, I started having chest pains and went to have it checked out. When they put me on a monitor, they asked if I smoked and I said no. I've never smoked in my life. They asked if I was sure and I said yes. They then told me I had significantly elevated levels of CO. My house is all electric, so nothing there. I blew this off until I saw your thread just now. Looks like I'm heading to the dealer.
 

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oldschool
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goplay,

I just saw this thread and watched your video. Is that a CO detector?

Here's my story. I have an '08 with 29,500 miles and have been getting a very noticeable exhaust smell in the cab on regen for some time. I'm around diesels all the time, so its not a big deal, or at least hasn't jumped high on the priority list for me.

A couple of months ago, I had been driving for about 2 hours in the truck coming back home on a short trip. Later that day, I started having chest pains and went to have it checked out. When they put me on a monitor, they asked if I smoked and I said no. I've never smoked in my life. They asked if I was sure and I said yes. They then told me I had significantly elevated levels of CO. My house is all electric, so nothing there. I blew this off until I saw your thread just now. Looks like I'm heading to the dealer.
that may not be your truck, you need really high levels of CO2 to effect you because its not poisonous it just displaces oxygen
I would think the carbon monoxide would effect you much sooner
 

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Mine did the same thing, untill I took off the Jet engine in my exhaust, every LMM I have ever rode in does it!!!! I heard it is due to a crack in the casting of the down pipes, that is why the dealers replace them.
 

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Update:

I took the truck into the dealer the morning of Thursday Dec 30th. Having the PIP number was extremely helpful. The service writer pulled it up for me and read through it, printed it out and attached it to the service write-up.

They called about noon on Friday and told me the pipe was cracked and would be replaced. I heard back Monday afternoon and they said they were still waiting on the pipe and hoped it would be in today or tomorrow at the latest. They offered a loaner and have been really easy to work with. It's the same dealer chain I bought it from, although the Chevy outlet is where I took it as it's about 15 miles closer to me than the GMC outlet.

A big thank you for the PIP number and the info everyone has posted on this board.
 

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thnk I will take mine back in AGAIN with this information and see what they say. Should be a general recall for safety if people are being affected by it this much.
 

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yep yep...
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I own a 08 GMC, and for the last year I've had a strong exhaust smell in the truck when the truck is sitting at idle. Usually when I've pulled up to a stop light, or after the truck has warmed up. I've taken it to multiple dealers and they can't find anything wrong with the truck.
My fuel mileage has been around 13 mpg.
Have any of you guys had this problem?

PDQUICK
my 05 has done it since it was new when its cold out, new manifold,and up-pipe gaskets and a downpipe later it still does it.kinda shitty.
 

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I am pulling the stock down pipe sat, I will find the crack and post some pics of it.
 

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We've been discussing this locally the past few days around the fire station and a few other venues. The collective "wisdom" is to buy a home CO detector and put it in the truck to see if it kicks an alert. I'm interested to know what kind of results someone would have in a truck that has the problem but is not yet fixed.

From the combustion chamber, diesels emit a number of gases including both CO and CO^2. A diesel does not emit as much CO as a gasoline engine, but is present in sufficient quantity to sicken or kill in a relatively closed environment such as a vehicle compartment, although its strong odor would likely cause someone to open a window before it became fatal. That being said, the volume of CO would be sufficient to elevate the level in the blood and at cause low to mild level symptoms, especially with exposure over an interval of a few hours or more.
 

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"THEEPASUCKS"
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The other day my truck went into Regen and while sitting at a stop light my pregnant wife said " I smell fuel ". Sure enough my Down Pipe is leaking!! Man that's BS. I guess it's time to get the aftermarket exhaust Honey.
:drink
 

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My truck got stuck in regen for an hour when I was on an interstate when it was stock, smell just about ran me out of the cab. I had to pull over and shut it off and start it five times before it stopped, dealer found no issues, and truck burned through 11 gallons in one hour at 70, so I ripped the jet engine out. If I had on o2 senor in the cab when it happened, I garrentee you it would have gone off!!! It was freakin cold and raining when this happened so could only crack the windows a bit. It took a full day for the odor in the cab to subside. This may have happened to you, convoyduel.
 

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Jank-A-Lank
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i smell exhaust also, have the 5" tb exhaust... probably a leak in the DP though.. thinking about doing an aftermarket DP
 
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