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Hello everyone.  I have a 07 400 ai in a mr cabover . Vin# 1m2k197c27m039374.  Am having serious power loss when petal to floor , feels like engine stumbles or derates to about half power only when petal is all or close to all way down. Max boost is 25 but goes to 0 when it stumbles.  Fuel pressure is 60 to 75 when its pulling under load . Replaced boost pressure sensor. Replaced injectors and adjusted valves. Makes no difference with muffler off. Checked for boost leaks. Reflashed ecm. Throws no codes . Weight is 56k at all times. What do i check next? My dealer isn't much help. Didnt know anything about a 12b throttle update or even how to check if i had it installed.   Next im thinking foot pettle, crank sensors.  Or what do u guys think? Thanks.

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I checked you VIN and you dont have the Step 12 B installed but that is not your problem. Throttle pedal or wires going from throttle pedal to VECU could be shorting to ground or rubbing. Check engine ECM connectors for coolant in the ECM.  Any J1939 fault codes inactive? Load test batteries, then check cables to starter and wires from starter up to AUX starter solinoid behind cab and also the ground breaker mounted there.

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According to Mack , You have the Powerleash engine brake. You might pull the valve covers and check the rocker arm hold down bolts. We see lots of the bolts break and cause the rocker arm shaft to bend and crack letting oil into the engine brake oil passageway causing the enging brake to engage enough to cause problems 

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I will swap a peddle out and see what that does. The only codes I have or had for last year was for one unit pump which comes and goes, it doesn't follow the problem.  It has very little smoke so seems to be under fueled. Wouldn't any of those issues set codes tho?

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JectAnd forgot to mention it runs rough a while when cold.  That was reason we put injectors in but now same issue with new injectors.

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17 hours ago, petehenry said:

Hello everyone.  I have a 07 400 ai in a mr cabover . Vin# 1m2k197c27m039374.  Am having serious power loss when petal to floor , feels like engine stumbles or derates to about half power only when petal is all or close to all way down. Max boost is 25 but goes to 0 when it stumbles.  Fuel pressure is 60 to 75 when its pulling under load . Replaced boost pressure sensor. Replaced injectors and adjusted valves. Makes no difference with muffler off. Checked for boost leaks. Reflashed ecm. Throws no codes . Weight is 56k at all times. What do i check next? My dealer isn't much help. Didnt know anything about a 12b throttle update or even how to check if i had it installed.   Next im thinking foot pettle, crank sensors.  Or what do u guys think? Thanks.

Have you monitored the fuel pressure During a power loss event? We had a part of a bread bag in our fuel tank in the 98 and caused a very similar issue. Got there from previous owner trying to get away temporarily with wrong fuel cap. If your a waste management application you have thousands of pounds of that kind of junk in your chassis work body most of the time. All it takes is one little piece to make a capillary flap. Nice to get the update if possible. Run the tank low and Have someone eyeball the tank while you blow air backwards down the pick up pipe.

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The fuel pressure stays 70 psi when power drops. This truck is on a concrete pump so it gets a lot of idle. When operating it runs 1300 rpm but it never stumbles than only when driving. 

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When codes don't appear for a really obvious, bad, running issue you start with cleaning/improving grounds. Grounds are the AIDS virus of a Mack EECU, ECM, ABS, VECU, etc....... the immune system just can't identify(code) it.     

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Thanks for all the help so far.  A update on this., ok so I cleaned all grounds no difference.  Changed intake temp sensor no difference.  Than I swapped out the eup that had been throwing a code intermittently and that fixed the power cutout issue.. now my question is do these eups get weak and underfuel with age? Truck has  10k hours and it still seems underpowered  my boost doesn't go above 25 and I don't have any smoke at all. And I put stage 1 injectors in when they was changed. 

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Did you get the 12b Mpro mentioned? Sounds like you flashed but did not update?

Personally, I’d replace all original EUP’s at a 10-12K hour interval. I have that number in my head from a cam failure that we had last year caused by two broken EUP springs @ 15k hours.

Spring frags also badly damaged EUP bores. Had to build a slide hammer extractor out of an junked EUP spring shoe to get followers out over knurled-up damage.

Unfortunite “Pay me now or pay me later” moment...... ended up with all new EUPs at that point.

Wouldn’t expect noticeably better performance from EUPs though. 12b.....major performance upgrade.

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No did not do the update. Local mack said they don't kno anything about it and they couldn't help me on that. So how do I make them aware that there's something out there like that?

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You shouldn't have to. It's more Gray Engine Amnesia. Hard to wrap my head around what is going on at the dealerships? Its the age of information and interconnectivity and folks can't get a software update? I'm guessing they turn-over mechanics so fast there is no archival knowledge being passes along inside the shops.

  

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I had to go to three different dealers before i finally found one who would update my 04 AI from 9B to 12B, and it took that shop almost half a day to actually get it to work, they had to flash it (called it that i believe) several times before it "took". Sounds like we are chasing the same intermittent low power issue

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On 3/28/2018 at 10:29 AM, Mack Technician said:

You shouldn't have to. It's more Gray Engine Amnesia. Hard to wrap my head around what is going on at the dealerships? Its the age of information and interconnectivity and folks can't get a software update? I'm guessing they turn-over mechanics so fast there is no archival knowledge being passes along inside the shops.

  

Finding people that give a rats ass about what they are doing for others these days is a struggle !  Its just a job , just a pay cheque, no pride in what little  work they do put out ,It is a real piss cutter trying to find good folks that want to work and want to please ,Having said that A lot of this mentality has been past down from the top mack / volvo its self is riddled with this same thought process ! Society in general  I Guess  Spoiled Brats! 

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Amen Fred!! Don't think I could have said it better myself.

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