So here's the deal - I leave Seattle on Friday to drive over the pass in the new truck. I've got just over 500 miles on it at the time of departure, so I should be through the initial 'break-in' period.

Things go fine right up until we're (the wife and I) heading up toward Crystal Mountain, a ski area here in Washington. At about 4000 feet altitude, the truck starts to 'cough'. The sound was like a cross between something rubbing the tire in the wheelwell and an engine stutter - there was no change in the RPM's that I could see. It only did it about 3 times over a 2 minute time period, for a few seconds each time, then everything ran fine. Once we got to the summit, we got out and I smelled something like burning rubber for a second, but I couldn't find anything that was burning. We get back in the truck, go down the hill, then head up the pass again, and it does the same thing at about the same altitude/elevation. Going downhill didn't bother it, it only occurred going uphill/under load. Coming home yesterday, same thing at about the same alititiude. Aside from this, the truck ran fine, but this sound worries me. A buddy thought it might be something to do with the O2 sensor, and the effect of thinnner air at altitude, but I'm not so sure... Again, ther wasn't any noticeable change in the RPM's, and there was only the SLIGHTEST (could have been imagined) feedback through the gas pedal...

Anybody got any ideas?

 

I have an '04 350 . I first experienced a similar "cough" coming from below my feet on the drivers side when I was climbing a long grade with my camper on the back. During the next 3 weeks of the trip I became familiar with the noise. It seems to happen at about 1700 rpm when the engine is starting to lug. If I kick it down into a lower gear it quits. One theory is that its the transmission failing to shift and "something" slips. I have also experienced it while towing my 7,100 lb. boat while climbing up a grade. I have mentioned it to my dealer and he says he can't do anything until I demonstrate it for him. I will probably take him for a ride when I next hook up the boat. Anyone else hearing this noise or have any ideas what it is?

 

Never having experienced that in 33k+ miles I can only offer general advice...

first - welcome to the site...
1) as far as the dealer saying unless you can demonstrate it to him ???
RUN away from that idiot !!! He should be able to diagnose without it being proven to him
2) understand the possibility of a gasser coughing at altitiude, but the 6-oh turbo runs right thru to as high as I wanna go with narry a slow down what so ever...

seems I recall a high altitude flash somewhere in the mix...

And if you are both Republik of Kalifornia trucks....

all the more reason to get your enviroidiots out of office !!!!!

the rest of the world is laughing at some of the decisions coming out of the left coast

 

Deisel trucks dont have O2 sensors..

 

You are right, they do not. They are, however, a valuable tool in a high performance buildup, in conjuction with an Air/Fuel Ratio gauge...

 

turbo "bark" or "flutter" or "fart" --whatever you want to call it. A common occurrence when letting the 6.0 lug down in overdrive. Overboost with no rpms to need it? Happens quite often on my '04--downshift and it won't happen, or use tow/haul and it will downshift sooner by itself.

Maybe the burnt smell is just new truck parts that are hot? Mine had all kinds of odd smells for about 2-3k miles, then no more.

 

I doubt you got feedback through the accelerator unless it was vibration. The accelerator is a rheostat that feeds info to the PCM. "fly by wire" so to speak.

 

Never had anything like that happen even when towing a 10,000 lb trailer over a number of grades.

The turbo cough only happens if you have a lot of boost and get out of the throttle all the sudden. If you are constantly on the throttle and still getting the coughs then it's something else.

Never had any kind of burning smell with my truck either.

 

I drive at high altitude daily and have pulled 7,400 lb load up long grades above 7,000 ft elevation many times... In fact, I have been known to pass sports cars going up the canyon to Alta & Snowbird ski areas just because I could (not with the boat in tow!). I've never encountered a cough or stumble as described. I was talking with a fellow 6.0 owner about a year ago and he told me that his coughed once at high altitude when it was quite new but that was it- He said that it never happened again.

Maybe it is something with the break-in... Or not. If possible, please report back on your progress whether positive or negative in resolving this issue. Good luck.