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Duramax Fuel Injector Question

Chili Palmer

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I’ve got 260k on my truck (2011 2500 HD) and a check engine light (P1287) came on for the throttle position sensor, in doing their check the shop also found that my #3 injector is requiring a higher demand than the other injectors. That injector has always been off in the balance rates, but within “spec”, even when my truck was new and under warranty, but Chevy’s response was always, “There’s no check engine light so everything is working as it should”. That was when I was complaining about regens at 300 miles and mpg no better than 15mpg. Now my question is - should I replace all the injectors while they’re at it? I’ll probably keep the truck for another 100,000 miles. What say you guys?
 

Bigbore500r

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I’ve got 260k on my truck (2011 2500 HD) and a check engine light (P1287) came on for the throttle position sensor, in doing their check the shop also found that my #3 injector is requiring a higher demand than the other injectors. That injector has always been off in the balance rates, but within “spec”, even when my truck was new and under warranty, but Chevy’s response was always, “There’s no check engine light so everything is working as it should”. That was when I was complaining about regens at 300 miles and mpg no better than 15mpg. Now my question is - should I replace all the injectors while they’re at it? I’ll probably keep the truck for another 100,000 miles. What say you guys?
Is it still within spec? The code it’s throwing doesn’t seem to be linked to your injectors or fuel flow related. At 260k I’d do all the injectors if I had to do one. If it’s still within spec and has always read that way I’d be tempted to leave it alone and just fix what’s needed to get rid of the TPS code. Ever had the CP4 replaced?
 

DoughBallin14

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Hard to say my lmm duramax has 280k on the original injectors but i have also always ran a pint of 2 stroke premix oil in my tank about once a month. I can check my rates with my efi live software and my number 5 and 8 injectors have always demanded more then the rest but still barely in spec and no codes or mileage difference over the years. If your gonna do one i would do all as well. And make sure that cp4 is replaced. Sounds like you have been lucky with the one you have. 👍🏽
 

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If its within spec I say leave it alone and just address the TPS. It's not broke so no need to fix it. Chances are while fixing an injector that's within spec something else will get damaged due to changing the injector and will need repairing.
 

Cdog

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If it's + or - 4 consistently I believe its out of spec but it sounds like you know the parameters. I do believe you can replace just one injector but its best to take it to a shop for programing/calibration after you do the install.

At 215k miles my lbz will throw a low fuel psi code every once in a while when its hot/summer/105+ degrees. I read it's pretty normal.

But you may benefit from installing a lift pump like the Kennedy or Fass 85 if it's not modified or tuned. I know I have one injector that's marginal but it well within in spec with the Fast 165 lift pump.
 

SBMech

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If you do one, do them all. Save yourself the time and frustration of doing them one at a time.

I'd do the pumps too at that mileage.
 

Chili Palmer

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Thanks for the replies, my truck’s been deleted at 100,000 miles and have been running a 150hp tune with a Fass 150 lift pump and I run 8oz of OptiLube XPD at each fill up to keep the CP4 well lubed for the last 160,000 miles. This one injector has always been around +3.x while the others have been at +/- 0.0 - 2.3. I haven’t checked the balance rates in the last couple of months, but las time it was sitting at +3.8 to +3.9, but it the truck ran fine so I didn’t pursue any repairs. When I deleted I kept the cat to keep the smell and noise level down, but when my mileage went down recently I thought maybe my cat was getting plugged with soot so I deleted the cat and that made no difference in the mileage department. I haven’t checked the cost of the all new injectors or replacement of the CP4 with a modified CP3 for the LML. Do they make a modified CP4 that doesn’t grenade so no additional tuning is needed as they need to do for the CP3 conversions? If I need to dump all this money into my truck that I’ll never see, I might just put it into a newer truck with less miles.
 

DoughBallin14

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Sounds like you have all the preventative stuff covered to keep that cp4 lubed and air free. I myself wouldnt be concerned going with a new cp4 again since tuning is becoming a real B lately thanks to all the social media vids!!

last time my mileage dropped off a fair amount like 3-5mpg below my normal. It happened to be a combination of a dirty as crap MAF sensor, not paying attention to my tire pressure (all my sensors are dead), and my air filter being dirty (i cleaned it good i thought) replaced it with a new replacement S&B cleanable for type. Boom gained all my mileage back.
 

Chili Palmer

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I’ve got a new air filter, I recently cleaned the MAF sensor, and my tires are running flat across at 55psi, all to no avail. I’m hoping this injector will bring my mileage up to where it should be and eliminate the smoke on moderate acceleration as this is supposed to be a clean tune.
 

shan

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I don't usually reply to these types of posts, but you have to realize the government has mandated that you drive a mobile emission test station. The OEs have to have diagnostics that are so good that when emission tested if all diagnostics have been run and passed, you're good. No tailpipe measurement. If you choose to modify your vehicle, you're on your own. This is why the spec. is so tight on the injectors. To echo what someone else said, if it's not setting a code don't worry about it.
 
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DaveH

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the only time injectors are needed is when you get a p0087 (low fuel rail pressure) code. i wouldn't touch them.
 

Chili Palmer

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I don't usually reply to these types of posts, but you have to realize the government has mandated that you drive a mobile emission test station. The OEs have to have diagnostics that are so good that when emission tested if all diagnostics have been run and passed, you're good. No tailpipe measurement. If you choose to modify your vehicle, you're on your own. This is why the spec. is so tight on the injectors. To echo what someone else said, if it's no setting a code don't worry about it.
But why is it that my truck in stock form would only get 14.5 mpg, but my buddy’s same identical truck, except his was 4x4 got 21 mpg when we went out to the river together? His would regen every 600+ miles and mine would regen every 300 miles. I think something was off in my truck and the computer was trying to compensate in another location to maintain the proper emission quantity, but it sacrificed my mileage by running rich and causing the DPF to regen so often.
 

DoughBallin14

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But why is it that my truck in stock form would only get 14.5 mpg, but my buddy’s same identical truck, except his was 4x4 got 21 mpg when we went out to the river together? His would regen every 600+ miles and mine would regen every 300 miles. I think something was off in my truck and the computer was trying to compensate in another location to maintain the proper emission quantity, but it sacrificed my mileage by running rich and causing the DPF to regen so often.
Well not saying it’s relevant but did you buddy have larger tires and not re cal the speedo. Just have seen it time and time again where so and so gets 24mpg and i get 16mpg. Go and check and the speedo is off because its not stock tires. I can go into efi live change my tires setting and make my onboard mpg calculator on the cluster say 28mpg if i want because its not counting properly.
i always do the gps mileage and calculate it at the next fuel fill up.
i know doesnt fix a problem just saying haha 😂

also on mpg i noticed i got worse mpg when i used cruise control vs driving and lugging it myself smoothly and paying attention to slower starts.

as DaveH said usually you wouldnt change any unless you had a code pop up or your trucks white hazing out the tailpipe or she is really knocking and clacking cold.
 

shan

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But why is it that my truck in stock form would only get 14.5 mpg, but my buddy’s same identical truck, except his was 4x4 got 21 mpg when we went out to the river together? His would regen every 600+ miles and mine would regen every 300 miles. I think something was off in my truck and the computer was trying to compensate in another location to maintain the proper emission quantity, but it sacrificed my mileage by running rich and causing the DPF to regen so often.
Well, I guarantee it wasn't running rich if you had no light. 21 mpg sounds suspect, maybe he has trouble with math.
 

DoughBallin14

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Well, I guarantee it wasn't running rich if you had no light. 21 mpg sounds suspect, maybe he has trouble with math.
I can get 24 on a good trip to the river from temecula to rice road thanks to a sweet tailwind going through the windmills. But I usually kill it all on rice road haha 😂 typically end up at around 19mpg
 

Chili Palmer

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Well, I guarantee it wasn't running rich if you had no light. 21 mpg sounds suspect, maybe he has trouble with math.
I got 20.3 one time - my buddy and I both have the same size tires 305-55-20’s. It was the frequent regens that just sucked up my mileage.
 
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