genoredstar Posted January 9, 2023 Share Posted January 9, 2023 Have a mp8 thats just not right. Had boost of 39 to 40 lbs now only 35 max. Injector cups done not long ago, 30 k miles. Was in for service and coolant leaks and needed a egr cooler replaced .Next was Radiator as it was deemed to be leaking as well. Seemed to run ok but a lil sluggish. Dealer pressure tested and found a leaky boot. It improved the boost to about 35 lbs max but not the original 40 psi. Still noticing a loss of performance and boost. Ocasionally I'd get an eats screen if the truck was started cold and air built slow. If i bumped throttle a bit and built air faster on warmup no alert. Also no code. Dealer cant find issue. Turbo replaced ,controller replaced, Egr valve and exhaust manifold were next. Still only 35 lbs of boost when i used to get a solid 40 on a cool morning .Dealer tested for combustion gasses in coolant, starts and runs fine/smooth but I can tell its not right. Need to linger in gears longer loaded. Also had previous issues with egr temp sensor going bad often, would lose a lil power before showing a code, then noticeable derate when code comes active. Dealer claims they tried new probe , but no change. Any thoughts?? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/ Share on other sites More sharing options...
Onyx610 Posted January 9, 2023 Share Posted January 9, 2023 First would be to check for boost leaks from turbo to intake manifold. Has anyone looked into the fuel pressure? We’re the cups done and old injectors installed? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520647 Share on other sites More sharing options...
genoredstar Posted January 9, 2023 Author Share Posted January 9, 2023 i'm thinking I need to stand over the techs as they are scratching their heads. The truck will be new if they keep relacing stuff. Not gonna pay for turbo or actuator or egr valve or manifold they broke the bolts in .I'm thinking could be an issue with cups or injectors. Maybe we start with leaks, ..... again and double check eveyrthing before moving to the next set of parts. Fuel pressure did cross my mind as well. no codes or cel debris or leaking fitting? sucking air or combustion gasses in fuel gallery? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520650 Share on other sites More sharing options...
Onyx610 Posted January 9, 2023 Share Posted January 9, 2023 Hahaha, yea you might just have to help point them in the right direction. God I hope you don’t have to pay for all those parts. Jesus….Yea start with the easy and cheap stuff. Really look over the charge air system, check fuel pressure, boost pressure sensor, fuel filters? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520652 Share on other sites More sharing options...
genoredstar Posted January 9, 2023 Author Share Posted January 9, 2023 Coolant loss, leaks kinda point to a pressurized cooling system to start, no? They claim the egr was leaking slightly, Turbo actuator had a lil play and turbo had a very minor bind or change in effort in its operation but neither made a difference when replaced, as the egr didnt have a noticeable effect when it was replaced. How can we narrow or test for bad cups or injectors if no codes? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520653 Share on other sites More sharing options...
Onyx610 Posted January 9, 2023 Share Posted January 9, 2023 Also fuel lines and banjo fittings have been known to get gummed up. Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520654 Share on other sites More sharing options...
Onyx610 Posted January 9, 2023 Share Posted January 9, 2023 Egr valve or cooler? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520655 Share on other sites More sharing options...
Onyx610 Posted January 9, 2023 Share Posted January 9, 2023 (edited) Also air compressor will pressurize the system. Edited January 10, 2023 by Onyx610 Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520657 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 first cooler, was in for a service and that popped up , then the egr valve and manifold upon subsequent returns This truck is on it's 4th motor. bought it at auction and it had warranty from a rebuild. the third motor new from mack blew up with 900 miles and out of original warranty, chronologically, but how do you not warranty a 900 mile boo boo. Took a lil wrangling and threatened a trip to the warranty office at corporate personally before they relented and shipped #4. When I put the #3 in they noticed it was deleted, after of course, and I paid for everything after the turbo, ouch23K. Hurt Mack more than ME though! What corporate dont know wont hurt them. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520658 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 was experiencing loss from external leaks, then after all those were fixed i still had a leak, replaced radiator, needed to go back as the bleed line to the tank was leaking. Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520659 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 So your cooling system is being pressurized? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520660 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 There’s a few other guys on here that are really good with these. Mackpro, Vmac3, and FJH. I’m sure Mackpro will be in here later. Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520661 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 cups were done about 6-8 months ago, Dont think they did the injectors Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520662 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 Also sounds like you check for exhaust leaks. I know you said all that was new but you never know… Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520663 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 No, Im theorizing that as a possibility Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520664 Share on other sites More sharing options...
Joey Mack Posted January 10, 2023 Share Posted January 10, 2023 4 engines in 8 years... Holy Crap!!! Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520666 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 I really appreciate all the help, I'm older more of a mechanical motor guy , electronic stuff is a bit confusing Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520667 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 It is even for some of the best, stick around we will get you sorted out. Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520668 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 I got introduced late in its tangled life. Thinking it got more brute strength than TLC, I'll make up for it. Now to think rationally or emotionally! only 750k miles I hope its not scarred emotionally from being molested 1 Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520669 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 Is the truck at the dealership or in your possession? Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520670 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 at my place, they wont even give me a bill yet as i texted the service manager and told him it aint running right. I cant find any specs on boost but I know they run around 40 psi at 13 to 15 hundred with foot firmly in it. He knows I know right from wrong, Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520671 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 Your correct Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520672 Share on other sites More sharing options...
genoredstar Posted January 10, 2023 Author Share Posted January 10, 2023 If im correct losing 5 lbs of boost is about 15 percent of my power in the middle of the torque curve Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520673 Share on other sites More sharing options...
Onyx610 Posted January 10, 2023 Share Posted January 10, 2023 Also fueling is affected with lower boost Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520675 Share on other sites More sharing options...
Mackpro Posted January 10, 2023 Share Posted January 10, 2023 Normally with a non-deleted MP8 33psi of boost is the max. If we got 35-40 the turbo actuator was sticking due to soot or not calibrated correctly. Also have had soot clog the turbo and restrict the VGT vains on the other end and cause low boot. We have had Mack reman turbos right out of the box not calibrated or the turbo VGT vains not moving full travel. Possibly turbo boost pressure sensor caked with soot can cause weird issues. Also the incorrect part number for the boost pressure sensor causes issues. If it were mine you Id have the turbo actuator remove and the stroke manually checked with gauge. I’ll attach pics . 1 Quote Link to comment https://www.bigmacktrucks.com/topic/71014-2014-chu-with-an-mp8-seems-to-be-low-on-power-and-boost/#findComment-520752 Share on other sites More sharing options...
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