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I need meds to deal with this truck. Boost problem


Bdenney
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2011 Pinnacle with MP8 505hp. We have had nothing but problem after problem with this truck since we bought it 7 months ago. $9,000 in just repairs and it's only got 350k miles. About a month ago I was driving it and out of no where it stopped building boost. I could hear the turbo spooling and a good amount of air pressure was coming out the air cleaner for some reason. I got back on the road trying to make it home and after a few minutes the motor started cutting out like it wasn't getting fuel for about 20 seconds then it all cleared up and started running perfect and back to building 40psi of boost like always. So we serviced it and it did great for about 3 days then done it again but it took a lot longer for it to straighten up and run good. We took it to M&k Mack dealer and they replaced the injectors. When I got the truck back I noticed it didn't have the power like it did before and it would only build 30psi of boost. It ran good just not as powerful for a few days then started acting up again but it's different symptoms this time. Sometimes it will run ok and out of nowhere it will start building boost really slow and will only build 15psi. Obviously it has hardly no power and the def gauge will go from empty to full just back and forth a few times and the exhaust temps will go really high like 800-900 degrees, I can hear a whistle but can find any boost leaks, and engine brake stops working or it will barely work and sound funny. It won't clear up and run right until I shut the truck off and let it sit for a while. I don't know what to do and the dealership acts like they can't find the problem. Please help!!!!

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Sounds like a EPA induced nightmare

I believe you've hit the proverbial nail on the head. I choose to run my 1986 RD with a 250 for many reasons....this being a big one. Suck, puff, Bang, Blow. Now those where the good ole days.

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Usually when you have boost issues and engine brake issues at the same time on an MP motor it is Turbo related. The sometimes working sometimes not working description you are giving leads me to believe it is the Turbo actuator on its way out. If the actuator fails or starts to act up it will not adjust your sliding nozzle/vanes internally to build boost. Sometimes it can be the actual internal turbo vanes/sliding nozzle but it's usually the actuator mounted externally on the Holset turbo. Your engine brake also relies on this actuator in the second stage of engine braking by producing a back pressure in the exhaust system. If the actuator acts up you will see both of these problems. The actuator is about $800-$1000 Canadian and must be timed when replaced by the dealer on a lab top. I've had a few go at about 700-800,000 kms of engine wear. We had one turbo that needed to be replaced on a 2013 because the internals seized up at 250,000kms. Hope yours is the cheap version of the fix. The turbo is expensive.

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We have a 06 rawhide working with us that acts the very same way. Now I know its an e-7 but, it has that vvg type holeset turbo on it. Dang thing shuts off at random times, starts right back up, sometimes boost is good(37-40) other times 10 or so. its enough to make me pull out my hair and its not even mine. Glad its not. Fact that an mp8 and an e-7 acts the same stupid way is odd, but look at the common link between the two. Turbo type. maybe not the same part for part but same thought never the less. We've thought about changing out manifold and turbo with one off a 03 460 but i guess Im not sure if it would ever run again.One of us out here needs to get to the bottom of this. Dealers dont want to deal with it.

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I agree with BBIGRIG, that it sounds like an issue with the turbo actuator, especially with engine brake issues coinsiding withe the boost issue. wncchuck also has a good point, as the oil wicking into the harnesses can cause strange electonic issues, including the actuator.

Edited by 29Bowtie
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