Possibly bad injector? Opinions Please! - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 22 (permalink) Old 12-06-2016, 12:04 PM Thread Starter
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Possibly bad injector? Opinions Please!

Just got back from a very long trip towing a 7K travel trailer from Albuquerque NM down to Ft. Lauderdale Fl and back.

This was my first opportunity to run the Duramax for the long haul with some weight behind it. Anyway, when I started out I was gettiing about 12mpg at
75mph. I thought this was great but after about 500 miles the following occurred, The truck went into regen and completed successfully, the fuel economy dropped during the regen (expected). I stopped for fuel and reset all the mileage in the dic. I started back out but my mileage was averaging about 9.5 and at one point was down as bad as in the high 7.

I have an edge monitor so I know the truck was not in regen so I thought I would check the injector balance to see if it might shed some light on the poor fuel economy. I took 2 samples about 5 minutes apart, these were at approx 70mph, fully loaded and engine at temp:

Inj 1: -3.8 -4.3
Inj 2: 2.1 2.0
Inj 3: 2.0 2.6
Inj 4: 0.5 0.6
Inj 5: -1.9 -2.0
Inj 6: 2.0 1.7
Inj 7: 0.1 0.3
Inj 8: -0.8 -0.6

You can see Injector 1 seems to be having a problem, (no 5 is not great also) watching it I have seen it go as high as -4.6, when the engine idles Injector 1 hovers around -2+. This is got me a little baffled, and if this was an LB7 instead of an LML I would be fairly confident injector 1 is bad.

The regens that took place were all normal and were triggered by mileage and not soot, about every 750 miles. The other thing I noticed is the engine seems a little noisier since this trip. Perhaps it might be a result of oil breakdown from the long trip. I am considering taking it to the dealer to have this checked out but am concerned the dealer will just blow it off because no codes have been set and the truck does not seem to be blowing any soot or smoke. Also as I understand it GM wont even think about replacing an injector unless it at least Plus or Minus 4 all the time.

I would think a truck with only 32k would not have injector issues but perhaps I am missing something with this. One thing I forgot to mention is this is still running a stock tune and is not modded yet. I really need to get this sorted out before the warranty is gone. Any suggestions?

The Dark Knight: 2013 Silverado Extended Cab 2500HD LTZ, Z71, Z82, Z71 Apperance pkg, Black on Black, 20" Alloys, CTS,
Stock LML but to be deleted when the warranty is over


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post #2 of 22 (permalink) Old 12-06-2016, 01:04 PM
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Where did you fuel up ? Lots of places are running the winter blend of fuel which doesn't give you as much mpg due to the biofuel and freeze point and all that. Also I think that you are suppose to check balance rates at idle. What about pulling hills ? Was your first tank mostly flat land and the second tank was through hills and mountains ? Did you change any of the aerodynamics on the trailer ? Did you top off trailer tires and confirm the trailer brakes are not dragging because of loose connections ? Just a few ideas. Hope you get it figured out.

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post #3 of 22 (permalink) Old 12-06-2016, 01:33 PM Thread Starter
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Originally Posted by SouthFloridaGMC View Post
Where did you fuel up ? Lots of places are running the winter blend of fuel which doesn't give you as much mpg due to the biofuel and freeze point and all that. Also I think that you are suppose to check balance rates at idle. What about pulling hills ? Was your first tank mostly flat land and the second tank was through hills and mountains ? Did you change any of the aerodynamics on the trailer ? Did you top off trailer tires and confirm the trailer brakes are not dragging because of loose connections ? Just a few ideas. Hope you get it figured out.
For the most part I was using Shell Ultra low sulfur Diesel for the full trip, I did start the trek with a full tank of fuel that was purchased the end of October so maybe it was a summer blend then as I burned that up the next tank would have been the winter blend you mention. As far as the trailer is concerned nothing changed and at each fuel stop I made I checked the brake drums for heat, and tire pressures, both were fine. As far as the terrain goes there was a slight difference in the amount of hills I encountered later on in the trip but nothing that I would consider a major difference.

I wasn't aware that the balance rates displayed are only valid at idle. I need to do a little more homework on that. This is so strange because everything else is perfect, 700 plus mile regens, trans was perfect and never got over 145 and the truck really pulls well. Running in the trailer mode at 75 up and down mountains it never even downshifted once. I guess I need to see what is reasonable fuel economy using winter blends both city and highway with no load and compare that with my results.
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post #4 of 22 (permalink) Old 12-06-2016, 02:13 PM
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Originally Posted by 2013LT2500 View Post
For the most part I was using Shell Ultra low sulfur Diesel for the full trip, I did start the trek with a full tank of fuel that was purchased the end of October so maybe it was a summer blend then as I burned that up the next tank would have been the winter blend you mention. As far as the trailer is concerned nothing changed and at each fuel stop I made I checked the brake drums for heat, and tire pressures, both were fine. As far as the terrain goes there was a slight difference in the amount of hills I encountered later on in the trip but nothing that I would consider a major difference.

I wasn't aware that the balance rates displayed are only valid at idle. I need to do a little more homework on that. This is so strange because everything else is perfect, 700 plus mile regens, trans was perfect and never got over 145 and the truck really pulls well. Running in the trailer mode at 75 up and down mountains it never even downshifted once. I guess I need to see what is reasonable fuel economy using winter blends both city and highway with no load and compare that with my results.
Where are you running on cruise control at 75 whereas you can't tell when the truck is pushing harder or softer unless it downshifts and you hear the change

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South Florida GMC
2011 GMC LML CCLB SLT DRW 4x4
285/75/R17 B & W turnover ball
Antitheft hose clamp installed on tailgate hinge
109,000 first cp4 replaced along with most of fuel system Airdog 165 added + Stanadyne Summer Formula
GM DRW Member #256
"The NOx Sensor is on the way out when you drive it out of the lot"
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post #5 of 22 (permalink) Old 12-06-2016, 02:30 PM
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Those MPG #'s are what I used to get in stock form towing about the same weight as you stated you're towing. LML's get garbage mileage in stock form! The truck will regen less frequently when pulling. The truck will perform a forced regen every 700 miles or whenever the DPF is loaded, which ever event occurs first. I know my LML would regen every 700 miles when on long trips while towing, regens occurred aprrox every 300-400 miles when the truck was empty depending on driving habits. My advice is, delete it and never look back!

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post #6 of 22 (permalink) Old 12-06-2016, 05:49 PM Thread Starter
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Quote:
Originally Posted by LMLADDICT View Post
Those MPG #'s are what I used to get in stock form towing about the same weight as you stated you're towing. LML's get garbage mileage in stock form! The truck will regen less frequently when pulling. The truck will perform a forced regen every 700 miles or whenever the DPF is loaded, which ever event occurs first. I know my LML would regen every 700 miles when on long trips while towing, regens occurred aprrox every 300-400 miles when the truck was empty depending on driving habits. My advice is, delete it and never look back!
I really want to dump the smog crap but waited (on good advice) to wait until my long trip was completed being under warranty just to make sure the truck was healthy before ripping it off and voiding the warranty.

The Dark Knight: 2013 Silverado Extended Cab 2500HD LTZ, Z71, Z82, Z71 Apperance pkg, Black on Black, 20" Alloys, CTS,
Stock LML but to be deleted when the warranty is over


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post #7 of 22 (permalink) Old 12-07-2016, 02:17 AM
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I really want to dump the smog crap but waited (on good advice) to wait until my long trip was completed being under warranty just to make sure the truck was healthy before ripping it off and voiding the warranty.
If your injectors are dirty or leaky, you should be part of the short regen club. An 8 oz bottle of power service diesel kleen + cetane with slick lube will most likely clear that up.
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post #8 of 22 (permalink) Old 12-07-2016, 05:22 AM
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Quote:
Originally Posted by 2013LT2500 View Post
I have an edge monitor so I know the truck was not in regen so I thought I would check the injector balance to see if it might shed some light on the poor fuel economy. I took 2 samples about 5 minutes apart, these were at approx 70mph, fully loaded and engine at temp:

Inj 1: -3.8 -4.3
Inj 2: 2.1 2.0
Inj 3: 2.0 2.6
Inj 4: 0.5 0.6
Inj 5: -1.9 -2.0
Inj 6: 2.0 1.7
Inj 7: 0.1 0.3
Inj 8: -0.8 -0.6
Any suggestions?
Balance rates are to be checked in park with a warmed up engine. In park they should not be above/below -/+4. If they check out fine in park, put drive selector in "D". They should not be above/below -/+6.

This is with a stock tune loaded on the truck

Report back with the new numbers.

Jim
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post #9 of 22 (permalink) Old 12-07-2016, 07:05 AM
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Quote:
Originally Posted by 2013LT2500 View Post
Just got back from a very long trip towing a 7K travel trailer from Albuquerque NM down to Ft. Lauderdale Fl and back.

This was my first opportunity to run the Duramax for the long haul with some weight behind it. Anyway, when I started out I was gettiing about 12mpg at
75mph. I thought this was great but after about 500 miles the following occurred, The truck went into regen and completed successfully, the fuel economy dropped during the regen (expected). I stopped for fuel and reset all the mileage in the dic. I started back out but my mileage was averaging about 9.5 and at one point was down as bad as in the high 7.

I have an edge monitor so I know the truck was not in regen so I thought I would check the injector balance to see if it might shed some light on the poor fuel economy. I took 2 samples about 5 minutes apart, these were at approx 70mph, fully loaded and engine at temp:

Inj 1: -3.8 -4.3
Inj 2: 2.1 2.0
Inj 3: 2.0 2.6
Inj 4: 0.5 0.6
Inj 5: -1.9 -2.0
Inj 6: 2.0 1.7
Inj 7: 0.1 0.3
Inj 8: -0.8 -0.6

You can see Injector 1 seems to be having a problem, (no 5 is not great also) watching it I have seen it go as high as -4.6, when the engine idles Injector 1 hovers around -2+. This is got me a little baffled, and if this was an LB7 instead of an LML I would be fairly confident injector 1 is bad.

The regens that took place were all normal and were triggered by mileage and not soot, about every 750 miles. The other thing I noticed is the engine seems a little noisier since this trip. Perhaps it might be a result of oil breakdown from the long trip. I am considering taking it to the dealer to have this checked out but am concerned the dealer will just blow it off because no codes have been set and the truck does not seem to be blowing any soot or smoke. Also as I understand it GM wont even think about replacing an injector unless it at least Plus or Minus 4 all the time.

I would think a truck with only 32k would not have injector issues but perhaps I am missing something with this. One thing I forgot to mention is this is still running a stock tune and is not modded yet. I really need to get this sorted out before the warranty is gone. Any suggestions?
Good Morning 2013LT2500,

We see that you are seeking the opinions of other forum members, so we would like to offer our assistance as well. We would like to get you in touch with a GM Certified dealership to get your current situation addressed. If you would like our assistance with this process, please send us a private message. Thank you and we look forward to hearing from you.

Philip J.
GM Customer Care
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post #10 of 22 (permalink) Old 12-07-2016, 09:32 AM Thread Starter
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Originally Posted by GMCustomerService View Post
Good Morning 2013LT2500,

We see that you are seeking the opinions of other forum members, so we would like to offer our assistance as well. We would like to get you in touch with a GM Certified dealership to get your current situation addressed. If you would like our assistance with this process, please send us a private message. Thank you and we look forward to hearing from you.

Philip J.
GM Customer Care

Thank you Phillip, Left you a private message!
Dan

The Dark Knight: 2013 Silverado Extended Cab 2500HD LTZ, Z71, Z82, Z71 Apperance pkg, Black on Black, 20" Alloys, CTS,
Stock LML but to be deleted when the warranty is over


Learn from yesterday, Live for today, Hope for tomorrow.
Albert Einstein
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