If you have a "lope" like this you have problems!

http://www.youtube.com/watch?v=LqOx9iQyBSA



If all trucks are suppose to sound like this

http://www.youtube.com/watch?v=DfNMgLNTqzA

then maybe I have a problem as well, cause might don't sound like that at all when warming up, not since I had injectors replaced.

 

That's exactly what mine sounds like... So what is the problem?

 

Sounds like which? the "vroom vroom" of the first vid or the "putt-putt" of the second vid? The "cut out test" the dealer did showed all ok, took it to a real diesel shop pulled them as they did a leak test all were weak-low, pulled them and found lots of carbon build up! Too much idling and/or pressure box?
New injectors and she runs like a dream! No more "lope" and no "putt-putt" like in second vid.

 

Mine sounds like the first. Very distinctive lope... New injectors?

 

Yup!

I would consider it, would be a awful mess if some of those "carbon" chunks dislodged from the tips and ended up doing the jiffy pop dance on top of the pistons!

 

Nice, Guess it is time to get a professional opinion.

 

it may be carbon or the injectors are not performing correctly, but worth a few hundred to find out vs thousands later?

 

Just sent this information to my loacl Cummins shop. Guess I will see how much it's going to cost. Might just get them to install my exhaust break while it is in there.

 

I notice mine does it more when it's below 1/2 tank of fuel. It was even sounding like it was missing/popping yesterday before I filled it. It was down to just under a 1/4 tank and the temps were in the high 20s.

 

Is there any chance that this could be like a rev limiter? Maybe when the high idle kicks on, the ecm sets the rev limiter to 1000-1100 rpm's and the idle is bouncing off the rev limiter? Just curious.

 

That could have something to do with it. What we need is a Cummins engineer here.

It would be nice to know what exactly happens when the grid heaters are activated. That seems to be when most of us are experiencing the bad idle. The strange thing is that even guys with grid heater deletes are having it so that leads me to believe it has something to do with the grid heater circuit but not necessarily the grid heater itself.

 

I know that this may seem a little out of place, but how old are your batteries? Do they have a good connection? Any corrosion?

The only reason why I ask that is that if your batteries are low, it does funny things to computerized vehicles.

Since it does it when cold (20*) & not when warmer, it may be a low current issue. The injectors are fired electronically.

Do a load test on the batteries to see if they are the issue. Also do a alternater charging test while you're at it.

I had a similar issue with a gasser & all it turned out to be was a battery that was starting to fail.

 

IT'S NORMAL

Read your owners manual.

 

-sean-

The reason there is this debate is that if it is normal then why don't all trucks do it? Sure they all have a slight fluctuation of the idle when the grid heaters are on but some of us get much more than that. The owners manual won't help us here......

I'm not too worried about mine because it still runs perfectly otherwise but if there was a simple fix to make it idle smoothly in the morning I would probably do it. That's just how I am...

 

Glad mine doesn't have the NORMAL lope or the NORMAL oil leaks or the NORMAL coolant disappearing or the NORMAL shutter or the NORMAL squeak