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+--- Thread: Cm871 bad fuel mileage and black oil soon after changing (/showthread.php?tid=8131)
Cm871 bad fuel mileage and black oil soon after changing - Jar90 - 03-27-2022
I recently bought a truck with cm871 its de-mandated I have a friend that has same engine and I get almost 1 mpg less then him and the oil on mine gets black week after its changed and his is clean what should I look into? His has everything stripped off of it and mine has everything on engine yet thanks
RE: Cm871 bad fuel mileage and black oil soon after changing - tree98 - 03-27-2022
Very first thing you need to do is have your program looked at by Rawze.
Whatever you do DON'T take the egr cooler or any other emissions components off your truck, even though they aren't operational, taking the egr cooler off blocks coolant flow to #5,#6 cylinder's and will cause water pumps to fail and also run those cylinder's hot.
In the meantime you need to pull the dpf and doc off to make sure that someone didn't just drill some 1" holes through the honeycomb. It needs to be 100% hollowed out and free flowing with no restrictions.
Also don't let anyone talk you into replacing your VG turbo with a fixed vane, DON'T DO IT!!!!
RE: Cm871 bad fuel mileage and black oil soon after changing - Jar90 - 03-27-2022
The dpf is bypassed so no problem there. Iv looked online and there are some kits made to bypass egr with coolant line and such does that take care of cooling cylinders?
RE: Cm871 bad fuel mileage and black oil soon after changing - Rawze - 03-27-2022
As far as the fuel mileage being low ... and oil turning black prematurely, thare can be a hundred plus things that can cause that. Do a proper oil sample and send it off to a lab. For all anyone knows, it could be getting coolant or fuel seepage into the oil, causing accelerated wear.. on not. It could just be a crappy delete program in the ecm causing excess soot, or missing block-plates still allowing egr gas into the intake, it could be a lot of other things too.
You also need to do a tune-up on it if it has not been done recently. That engine still needs a lot of its sensors to run properly.. even after a de-mandate. Replacing the IMAP and exhaust gas pressure sensors (and ensuring the feed-circuit is not blocked up for it) if they are more than a couple years old.. a proper turbo inspection .. pressurizing the engine up to 30 psi and checking for boost/CAC leaks etc., ... and doing a proper injector leak test, etc.etc.etc.
-- These engines do no heal themselves.. they do not have internal fix-it sauce inside them.. they need proper maintenance and regular care for them to run correctly and not give issues or have lower than normal fuel efficiency. - NOT doing proper and regular maintenance will cost someone big time by letting things go .. even a little bit.
- Also, How much boost does it make in a hard pull?.. What is the pyro temps in a hard pull?.. etc.?
The First and biggest priority however is to have the program reviewed to see if it is a trash delete program. That is one of the biggest plagues in the trucking industry with regards to de-mandated trucks. More then 90%+ of all de-mandate programs are extremely hard on the engine and absolutely will cause pre-mature failures like fretted liners, blown head gaskets, repeating turbo failures, etc. So start by Copying the program out of the ecm and e-mail it to me for a review. I will tell you if it is harmful to the engine or not... or if it is contributing towrds lower than normal fuel mileage, etc.
RE: Cm871 bad fuel mileage and black oil soon after changing - tree98 - 03-27-2022
(03-27-2022 )Jar90 Wrote: The dpf is bypassed so no problem there. Iv looked online and there are some kits made to bypass egr with coolant line and such does that take care of cooling cylinders?
Most of these aren't worth using. There's really no need to go through the effort of taking the cooler off and using some other type of set up. Just leave the cooler on it. Have the (exhaust gas) ends welded shut if your worried about it leaking internally.
Eliminating things on the engine that are legally required to be there is a mistake. Your opening yourself up to problems from a very simple visual inspection by the wrong person. I know they don't happen often in most places but why take an un needed risk?
RE: Cm871 bad fuel mileage and black oil soon after changing - Jar90 - 03-27-2022
(03-27-2022 )Rawze Wrote: As far as the fuel mileage being low ... and oil turning black prematurely, thare can be a hundred plus things that can cause that. Do a proper oil sample and send it off to a lab. For all anyone knows,
...
I figured I'd do oil sample here soon. Highest boost iv seen is 35-38 it doesn't smoke hardly at all the turbo does seem to hesitate a little sometimes when you give it throttle...I wondered about that too if everything was blocked off like it should could it be possible they didn't block intake off its still all hooked up? I'm running t4 rotella oil in it...just had new injectors put in it and overhead ran also new fuel pump
RE: Cm871 bad fuel mileage and black oil soon after changing - Rawze - 03-27-2022
(03-27-2022 )Jar90 Wrote: .......just had new injectors put in it and overhead ran also new fuel pump
this does not mean it will pass an injectro leak test. .. Why were the old injectors replaced?.. did anyone bother to test them properly before blindly throwing money at it?
here is how to do a proper injector leak test on a CM871...
http://rawze.com/forums/showthread.php?tid=7747&pid=67948#pid67948
also, like already mentioned.. copy the program out of the ecm (using the Calterm softare) and e-mail it to me. That is another place to start towards ensuring things are done right.
RE: Cm871 bad fuel mileage and black oil soon after changing - Jar90 - 03-27-2022
They got replaced because 3 of them didn't pass cut-out test and they got replaced then ran fine.ok I'll ask my local shop to do that and then do I just send it to the email address you sent me code on?
RE: Cm871 bad fuel mileage and black oil soon after changing - Rawze - 03-27-2022
(03-27-2022 )Jar90 Wrote: They got replaced because 3 of them didn't pass cut-out test and they got replaced then ran fine.ok I'll ask my local shop to do that and then do I just send it to the email address you sent me code on?
sure