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Idle surge when setting park brake


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New to me 2012 CXU Mdrive with MP7.  Truck starts, runs, drives fine.  But when ever I come to a stop and set park brake it’ll start “surging” or “erratically idle” going from 600 to 700rpm.  It does eventually work out if it.  It will be idling at 650, set the park brake then immediately goes under load or bogs down to about 600 for maybe 1/4-1/2 second then let’s go and idles up to 700 then the process just continues, bogs down to 600 then “let’s go” and surges to 700 over and over. I tried disconnecting the throttle potentiometer behind the pedal but it continued.  It does seem like it only does it after the truck is warmed up.  

I do have a video but it is too big to upload to here.  
 

thank you 

Edited by E5Farmer
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I need to think on this one, my knowledge on this truck is dwindling.  however, there should be some really smart guys on the way to help.. jojo

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18 minutes ago, Joey Mack said:

I need to think on this one, my knowledge on this truck is dwindling.  however, there should be some really smart guys on the way to help.. jojo

Thank you.  I wish i could upload the video so guys could see and hear it.  

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I have a suggestion ! take part and clean the EGR DPF ports and tubes make sure all is clear! that surging you hear may be the EGR valve tryng to find its sweet spot and restricted tubes can make it slow to respond!

 

Just something to try!

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2 hours ago, fjh said:

I have a suggestion ! take part and clean the EGR DPF ports and tubes make sure all is clear! that surging you hear may be the EGR valve tryng to find its sweet spot and restricted tubes can make it slow to respond!

 

Just something to try!

Thank you.  The truck is deleted

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3 hours ago, Joey Mack said:

what are the most recent repairs that were done?  were any updates done to the TCM? 

The truck is deleted if that answers the question.  It’s a new to me truck

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21 minutes ago, E5Farmer said:

Thank you.  The truck is deleted

These typically don’t work out well. However tcm software like Joey said is a good place to start. How long have you had the truck and did this problem just start?

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I feel like the deleted automatic trucks especially with the already problematic mdrive have a lot more room for error without spot on delete software. There is alot of talking between the ecm, acm, and tcm. 

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5 hours ago, Onyx610 said:

These typically don’t work out well. However tcm software like Joey said is a good place to start. How long have you had the truck and did this problem just start?

I have only owned the truck for a couple months and it was deleted when i purchased it, its been doing it since day one.  I originally thought it idled too low.

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5 hours ago, Onyx610 said:

I feel like the deleted automatic trucks especially with the already problematic mdrive have a lot more room for error without spot on delete software. There is alot of talking between the ecm, acm, and tcm. 

Yes i would agree.  The truck runs fine 99% of the time so I’m not going to be spending big $ bringing it to a dealer or anything.  Just every now and then it does this.  I figured I’d try figure it out during the off season.  

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Ok, so we can eliminate that it’s not something new and that it didn’t have anything to do with the delete….Do you know the person that you bought it from? If not maybe someone sold it for this reason? 

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Glad to hear it’s running good for you, yea that makes sense on trying to get it figured out during slow times. Mack dealer near you? Maybe see about software updates for the tcm? It’s a start. tech tool could tell a lot too. Also see if you can get a smaller video to upload. I’d like to see this 

Edited by Onyx610
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Just now, Joey Mack said:

Our Mack dealer wont work on a deleted truck..  I hope he can get some help..   jojo

That’s what I figured would happen….

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yeah, it sucks in a way.... the last year I was working there, we had one come through, and I fixed it, 14 litre Series 60. I did the front cover.  While doing the work ,I found the EGR was capped off... It was a clean looking delete.  I was told to get this truck back together and out of here, then got my ears filled up with the rules about deleted truck's...  jojo

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42 minutes ago, Onyx610 said:

Ok, so we can eliminate that it’s not something new and that it didn’t have anything to do with the delete….Do you know the person that you bought it from? If not maybe someone sold it for this reason? 

I cannot say it is something from the delete or not as it was deleted when i bought it was doing this since i brought it home.  It could possibly be the reason he sold it.  But what i was told is they were going away from automatic trucks on their farm.  This issue could very well be the reason.  I’m guessing its fixable, just getting to that point!  Thanks 

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32 minutes ago, Onyx610 said:

Wonder if your clutch is engaging and disengaging quickly when in park. 

That sounds like a good possibility.  Would that be a computer fix you think?  Or clutch job?

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38 minutes ago, Joey Mack said:

yeah, it sucks in a way.... the last year I was working there, we had one come through, and I fixed it, 14 litre Series 60. I did the front cover.  While doing the work ,I found the EGR was capped off... It was a clean looking delete.  I was told to get this truck back together and out of here, then got my ears filled up with the rules about deleted truck's...  jojo

YUP!  I was told dealers do not like to work on them.  Luckily i have a couple local shops that don’t care.  

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23 minutes ago, E5Farmer said:

That sounds like a good possibility.  Would that be a computer fix you think?  Or clutch job?

It’s controlled by air, I believe there is a ribbon wire in the tscm that is know for problems and gets replaced. 

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