Coach goes into limp mode

[Laurel Moore]

My daughter has a 2011 holiday rambler Ambassador with a unusual problem. Transmission goes into limp mode, engine drops to600 rpm. You can turn key off restart engine  and go. It has been to 3 different Cummings shops ,codes show no  problem.any input would  be appreciated.

[Mike Shumack]

Why do you say it is in "limp mode". Are you getting an engine warning light?

What engine (I assume Cummins) is in the Coach?

Possibly you have a bad throttle (accelerator pedal) position sensor (engine issue and not transmission related).
Do you have any throttle (rpm) control when this happens?

[Rick Daniels]

Nearly every diesel-powered vehicle built since 2010 is equipped with Selective Catalytic Reduction (SCR), meaning they require Diesel Exhaust Fluid (DEF) to function.  DEF has a shelf life.  I have had more than a couple DEF required diesel engines that were seldom used and exhibited the same symptoms when taken out of storage and the "limp mode" was caused by bad DEF.  Don't know if the 2011 Holiday Rampler required DEF.  Even though the coach is a 2011, the chassis may have been built prior to Jan 1, 2010 and would likely not require DEF.

[Joel Ashley]

Rick’s assessment sounds more plausible, but it could also be low coolant level in a surge tank.  When we once experienced a failed hose, the level went below the tank’s sensor which then protected the engine by “derating” it.  It could be your daughter’s tank fluid is just at that place where at a certain temp point/level and/or road crown it sloshes away from the sensor. 

Joel

[Bill Lampkin]

You may want to Google Irv2 and try their boards for Holiday Rambler and another for Cummins engines. Hope I'm not running afoul of the rules here.

[Laurel Moore]

All answers to my problem sounds like real possibilities I will check each one out and let you know my findings thanks a lot

[Laurel Moore]

Rick , this coach was setting a lot, did you add def  to solve the problem?

[Laurel Moore]

It is a max force engine , no Def. when this happens  rpm @ 500  dash lights trans fail note.turn off restart and go.it seem to be more electrical.

[Rick Daniels]

Hey Laurel, I assumed it was a diesel pusher either Cat or Cummins.  In my case I had to drain the DEF tank and add new DEF and all was well.  I am totally ignorant on Max Force engines.  Sounds to me like a sensor problem of some kind but that's an ignorant shot in the dark.

[Rick Daniels]

Some of the 2011 - 2014 Max Force diesel engines were subject to a class action law suit wherein they were found to have not complied with the "Def" requirement in all vehicles manufactured after 2010.  Yours may be one of those diesel engines that hit the market without a "DEF" system.  If yours is Diesel and was manufactured after 2010 without a DEF system it is out of compliance on EPA rules.  I don't know the details or the final outcome of the law suit but It's worth time to check it out.  You would think that some accommodation must have been made for the benefit of persons who bought them.   

[Gerald Farris]

Rick,
None of the Max Force engines from 2010 to 2014 used DEF. Navistar used an EGR (exhaust gas recirculation) system to reduce nitric oxides instead of DEF. The problem with the system, other than it did not furnish adequate reduction, was that there was inadequate design and testing of system components that lead to very high maintenance and down time for the trucking industry. That is the reason for the law suits over the engine, and Navistar has lost many of them. The most expensive design flaw issues are related to EGR coolers that last only 20% of the engine design life and repeated turbo charger failures.

If you are having problems with a Navistar EGR engine, you would be well advised to take it to a Navistar (International Truck) dealer instead of a Cummins dealer. The two engines have a very different design when it comes to operating systems.

Gerald

[Rick Daniels]

That's interesting Gerald

That explains why my son in law, who owns a trucking company, has always said stay away from Navistar engines.  As to Laurel's issue I, with less than novice knowledge of diesel mechanics, would suspect a connection to the Navistar EGR system.  I have always believed that one should always rely on Cat dealers for Cat problems, Cummins dealers for Cummins problems and now Navistar for Navistar problems.