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Discussion Starter · #1 ·
So it's basically the same thing right? Am I welcome here?

I have a 2016 Canyon Diesel.

My truck has had amazing MPG since I purchased it a bit over a year ago (31-37mpg highway, 23-27mpg daily backhills/mixed, 21-25 towing my 3k lb trailer) 600-650miles range per tank.

It felt very powerful, as though the babymax could idle uphill and was nothing to drive on the highway.

Till about 3 months ago, it definitely became noticable that it was requiring more throttle to even keep pace on a flat highway, and the MPG was reduced significantly.

I know that my truck wasn't RATED to get those MPG numbers, but I was tracking it and matching it at the pump and I appreciated what I had, and I definitely have read reviews saying most people got better results than the official numbers. ...Anyways.

I take care of it, I got it at 31k miles, I keep tire pressures at 34-35psi... prefer quality DEF and fuel, all services ahead of schedule(severe)

I thought maybe it was just a tank of bad diesel but it's been at least 7or8 fillups since, and midways I replaced fuel filters, air filters, and had oil, brakes, transmission fluids serviced at GMC dealership and they didnt note anything on their multipoint inspection.

I have no warning lights, the onstar monthly report (garbage) is all green.

But I'm getting 16-19mpg towing, 18-24 daily backhills mixed, and 20-29highway. Pissed off, I had to pinch myself to be sure I wasn't back in a gasoline truck...

I don't know much about variable geometry turbos and fuel systems but I would hope that this would have triggered some kind of service indicator.

I signed up here hoping to ask these questions, and learn.
 

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So it's basically the same thing right? Am I welcome here?

I have a 2016 Canyon Diesel.

My truck has had amazing MPG since I purchased it a bit over a year ago (31-37mpg highway, 23-27mpg daily backhills/mixed, 21-25 towing my 3k lb trailer) 600-650miles range per tank.

It felt very powerful, as though the babymax could idle uphill and was nothing to drive on the highway.

Till about 3 months ago, it definitely became noticeable that it was requiring more throttle to even keep pace on a flat highway, and the MPG was reduced significantly.

I know that my truck wasn't RATED to get those MPG numbers, but I was tracking it and matching it at the pump and I appreciated what I had, and I definitely have read reviews saying most people got better results than the official numbers. ...Anyways.

I take care of it, I got it at 31k miles, I keep tire pressures at 34-35psi... prefer quality DEF and fuel, all services ahead of schedule(severe)

I thought maybe it was just a tank of bad diesel but it's been at least 7or8 fillups since, and midways I replaced fuel filters, air filters, and had oil, brakes, transmission fluids serviced at GMC dealership and they didnt note anything on their multipoint inspection.

I have no warning lights, the onstar monthly report (garbage) is all green.

But I'm getting 16-19mpg towing, 18-24 daily backhills mixed, and 20-29highway. Pissed off, I had to pinch myself to be sure I wasn't back in a gasoline truck...

I don't know much about variable geometry turbos and fuel systems but I would hope that this would have triggered some kind of service indicator.


First off Welcome to the group.

I am wondering how "in tune" you were with a regen cycle when they happened? and are they similar to past regens in reference to mileage traveled between regens.

As far as the turbo goes, there is an actuator that moves the veins. It's an external box with a linkage rod between the controller and the tubo. I would check that for a proper mechanical connection. If you have access to a scanner I would want to check the turbo pressure while driving to see if it's inline with others on the board. If you have a leak in the intake you should hear it blowing when you dig into the pedal, also that should throw a CEL. I would also jack up each tire and give em a spin to make sure a caliper does not have a hung piston putting drag on the vehicle and that goes for the rear dif as well. If the truck is 4WD did you accidentally hit the selector while getting in the truck and put it into "Auto 4WD High".

Maybe this will give a starting point and you have my interest peaked please let us know what you find.

This link will give you some more input on the turbo

 

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If I had to take a stab at what your problem is, I would hazard to guess either the DPF or the EGR is starting to plug up. Mainly since you mention that you can noticeably tell that it takes more effort for it to go up a hill or even on the highway. And that your MPG’s have dropped.

How many miles were on the truck when you bought it and how many do you have now?
 

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Discussion Starter · #4 ·
These are great starting points! And thanks for welcoming me! I never specifically notice the regen cycles and I wish it indicated them. But I generally travel about 70 miles of continuous highway driving twice a week so I assume it usually regens then. I usually drive with the last 25miles MPG display up. When this started, I assumed I was just noticing an instantaneous MPG drop and higher effort during a regen cycle, but when it never resolved I began to pay close attention. I don't think it burned through the last tank of DEF surprisingly fast. And regen is automatic correct? Regen should be cleaning the DPF I thought...?

Checking the turbo isn't something I think I'd feel comfortable doing at my knowledge or experience level, but it was one of my suspicions and if you verify that, I'd like to take it to someone who knows what they're doing.

I'll certainly jack up the wheels and check for free-spinning. I'm methodical about getting into the truck so I know for a fact that it wasn't in 4WD (part of my driving sequence is making sure that poorly placed knob is twisted all the way to the left with the 2wd LED light indicator lit) I have obsessively been considering whether there's possibly a tinge of alignment or drag on any of the wheels that are being overcome by electronic stability or I'm just not noticing it enough.

I've had the truck since buying it 09/18 at 31K miles. As I stated, from September to June, my fuel efficiency was remarkable I managed a 2000mi round trip to Michigan in February at 29mpg. I got 37mpg on a 170mi trip from my home to the lake and back on May 16th this year. Oil changes at 34k, 38k, two months ago at 42k, and 2 weeks ago at 46k. I did 4000mi in two months because we travel with a 1ton sailboat on a trailer. it was after the June oil change that my efficiency dropped, but neither replacing air filters and fuel filters in august nor the oil change (and brake fluid, trans fluid, flushes) in September would fix it.

If its the DPF or the ERG or the Turbo I think i'd probably take it to a diesel specialist but I dunno, haven't looked into what you've suggested enough. Thanks, and for your continued thoughts! This forum seems too good to be true. I look forward to reading thru and learning as much as possible.
 

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These are great starting points! And thanks for welcoming me! I never specifically notice the regen cycles and I wish it indicated them. But I generally travel about 70 miles of continuous highway driving twice a week so I assume it usually regens then. I usually drive with the last 25miles MPG display up. When this started, I assumed I was just noticing an instantaneous MPG drop and higher effort during a regen cycle, but when it never resolved I began to pay close attention. I don't think it burned through the last tank of DEF surprisingly fast. And regen is automatic correct? Regen should be cleaning the DPF I thought...?

Checking the turbo isn't something I think I'd feel comfortable doing at my knowledge or experience level, but it was one of my suspicions and if you verify that, I'd like to take it to someone who knows what they're doing.

I'll certainly jack up the wheels and check for free-spinning. I'm methodical about getting into the truck so I know for a fact that it wasn't in 4WD (part of my driving sequence is making sure that poorly placed knob is twisted all the way to the left with the 2wd LED light indicator lit) I have obsessively been considering whether there's possibly a tinge of alignment or drag on any of the wheels that are being overcome by electronic stability or I'm just not noticing it enough.

I've had the truck since buying it 09/18 at 31K miles. As I stated, from September to June, my fuel efficiency was remarkable I managed a 2000mi round trip to Michigan in February at 29mpg. I got 37mpg on a 170mi trip from my home to the lake and back on May 16th this year. Oil changes at 34k, 38k, two months ago at 42k, and 2 weeks ago at 46k. I did 4000mi in two months because we travel with a 1ton sailboat on a trailer. it was after the June oil change that my efficiency dropped, but neither replacing air filters and fuel filters in august nor the oil change (and brake fluid, trans fluid, flushes) in September would fix it.

If its the DPF or the ERG or the Turbo I think I'd probably take it to a diesel specialist but I dunno, haven't looked into what you've suggested enough. Thanks, and for your continued thoughts! This forum seems too good to be true. I look forward to reading thru and learning as much as possible.
I mean, you don't have a great lot of miles on the truck. If you had 100k or greater, I might suspect a clogged EGR or DPF. I will say I have heard freak instances of those plugging up prematurely on a few trucks.

The DPF goes through regen cycles usually in the background without you knowing, so long as you get the truck above 45 mph I believe for at least 20 minutes. Usually occurs every....500 miles or so I think. You can notice it happening if you notice your instant MPG's drop off (say they normally run around 26 mpg and all of a sudden on nice flat ground they drop to 21) for a while. It drops off because extra fuel is being injected into the DPF as it will burn off the soot that has collected. You can also notice a funny smell at the exhaust when it is occurring. You might also notice that the truck is more "peppy" as I believe the EGR closes off while the DPF is doing a cleaning cycle. But, the DPF burns aren't a perfect burn, so over time, soot will continue to collect and eventually plug up.

There was an individual on here, Mr. Bones, who had issues with his DPF. He believed that his struck was constantly in regen as his MPG's were always awful, like sub-20's. Finally convinced the dealer to look at it and they did find that his DPF was constantly injecting fuel into the DPF I believe. He no longer participates on here I believe and has since sold his truck, but it's still good info.

The EGR will plug up too, as it recirculates exhaust gasses back into the engine to create....higher combustion I think? Can't remember fully what it does, but it's not pretty. So, you will get gunk that builds up in it and eventually it will plug too.

But, unless something isn't working right, you shouldn't have to worry about this happening until like...150-200k miles?

As for the turbo though, why did you suggest looking at that? I did not mention it myself and no one else in this thread has. The only way you would have a turbo issue is probably if you had dealt with freezing temps lately and possibly sucked a chunk of ice into the turbo. I reference that because our trucks have a known problem with doing that. Condensation will make it's way past the air filter and end up freezing once you shut the truck off. When you start it up again, it will break loose and impale itself on the turbo fins. It's actually not hard to check. I didn't feel like removing the hose going to the turbo, so I got an endoscope and ran it up in there to check on mine. Thankfully, mine is still good but I am still taking preventative measures. Also, bent turbo fins may generate a funny noise that doesn't sound normal to your typical engine noises.
 

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Discussion Starter · #6 ·
Thanks, will keep looking into it.

SFLTRUCK suggested I check the turbo actuator linkage rod for proper mechanical connection.

I didnt want to sound paranoid but I seriously have wondered whether it's just been stuck in a constant regen state!! But also I hadn't noticed DEF draining extremely fast... I dunno.

As always, thanks. Like Mr Bones, I think I need to take it back in and tell the mechanics what I'm experiencing.
 

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The DEF won’t drain super fast even if the truck is in constant regen. I don’t believe at least. I believe DEF usage is related to load on the truck. So, the more you ask from the truck (say you were towing a lot) you would go through more DEF.
 

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Thanks, will keep looking into it.

SFLTRUCK suggested I check the turbo actuator linkage rod for proper mechanical connection.

I didnt want to sound paranoid but I seriously have wondered whether it's just been stuck in a constant regen state!! But also I hadn't noticed DEF draining extremely fast... I dunno.

As always, thanks. Like Mr Bones, I think I need to take it back in and tell the mechanics what I'm experiencing.

Burgess is correct one has nothing to do with the other. DEF fluid is an after treatment deal down stream from the DPF filter. DEF use depends on engine load whereas the regen is set to start on a pressure differential pre and post the DPF, two separate systems
 

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And this what the thing that shall not be named is made for. At least it would narrow down possibilities, but thanks to our not so beneficent dictators at EPA, no longer a legal option.
 
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