V6 engine stumble

Jbernielh

Active member
my wife has had her RV for a few years now.. almost 60K miles on the 2010 with V6.. this tendency has happened for as long as she's had it, and it doesn't seem to matter if it's warm weather or cold.. as an aside the fuel filter has been replaced a couple times and that hasn't changed matters..

I'll start the vehicle and back it out of my shop (level ground) then into drive, and then go to start up an incline towards the house (engine started fine after waiting for glow plug light to go out) as soon as I start to roll ahead the engine starts to stumble as though one cylinder isn't firing.. I stop and put it into park or neutral, rev the engine 2 or 3 times up to 2K RPM (roughly) and then it's fine..

this only happens when the vehicle has been sitting without being started for a month or two.. if it's being driven on a regular basis never an issue.. I've thought about air in the fuel system or possibly a bad glow plug on one cylinder and it's not lighting off that cylinder but what is strange is that it idles smooth when I back it out and doesn't start to do this until I'm going forward and starting to put a bit of load on the engine..

I had just plugged the scan gauge in before this happened just to see if there were any codes or stored codes and it was all clear.. the first time I had experienced this was just after I'd done an oil service, air cleaner etc and thought maybe there was air in the system from replacing the fuel filter.. she purchased the vehicle with 22K miles and who knows if the previous owner had seen this issue as well..

not a big issue as it always seems to quickly resolve itself with a few quick rev ups.. just curious if anyone else has experienced this with a vehicle that has been sitting for a couple months..

Bernie
 
Try cleaning your EGR valve. Makes a big difference if it is dirty.
It is almost certainly dirty if it has not been cleaned in 60,000 miles.
 

Jbernielh

Active member
appreciate the thoughts

I pulled the EGR on spec at about 40K miles and cleaned it.. I was actually surprised how clean it was.. not sure if it's because most of her miles are highway miles with her foot in it, or not..

in regards to the stumble, it was doing it both before and after I'd cleaned the EGR.. it hasn't run now for a month, and I'm confident if I go to drive it right now it will do it.. then after that it will be fine..

Bernie
 

Aggie

2010 Roadtrek SS Ideal
I have a 2010 with about 118,000 kms, never had this experience. Mine is an RV as well that often sits several weeks, between drives. Always serviced near recommended intervals by MB Sprinter shop. ???
 

mdhutch2

Member
My 2012 will do exactly the same thing and the problem is worse the longer it has been sitting. 98% of the miles it gets are travel miles. Mostly highway but plenty of boondocks. Not much city driving at all.

After two different trips and then letting it sit for months it has completely stalled, after backing out the driveway and proceeding down the street, down a slight grade. It always runs fine after that. The last time at about 50000 miles the local dealer had it for almost two weeks trying to duplicate the problem but found nothing. No codes, zip, nada. Incidentally this was not too many miles after a warranty EGR replacement and a few months before that new NOX sensors.

That dealer, another dealer, and an independent shop all suggested that letting it sit is the probable cause of the stalling/stumble but none of them could spell out a mechanism. Two of them also suggested that driving too gently (to save fuel) allows things to clog up a bit possibly leading to problems down the road.

Since then, I've driven it more vigorously and not let it sit more than 2 or 3 weeks at most. I try for a long enough drive to get the engine completely warmed up at least every 2 weeks. I'm at 85000 miles now and it has never run better. Fuel economy is only a tiny bit worse. I will still get a stumble now and then but only if I forget to drive the van around often enough.
 

Jbernielh

Active member
thanks Hutch..

this one has never stalled.. just the stumble.. and always right after having backed out of the shop and going into drive.. up to that point it runs smooth and started fine.. as I said earlier, a quick pop into neutral, rev it up a couple or three times and it's smooth as glass..

I always felt it would be a gremlin if I took it anywhere to be diagnosed and that it would be a non repeatable situation.. I don't even know if it was air in the fuel system and you just happened to have it hooked up to a fancy scanner at the time if you would even see anything as the event happens, and is gone so quickly..

I certainly have no intention to pursue it, thx again

Bernie
 

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