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Engine "lugging" behavior

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Lugging might not be quite the right term, but, I've got a question as to whether the following behavior is normal for these new Cummins electronic engines.



This is on a '07 Megacab 5. 9 with the G56 manual trans. When driving around empty, just going to town, whatever, if I slow down to say, to make a turn and leave it in gear, when the engine gets near idle, it'll surge and try to speed up. If, for some reason it doesn't get to speed up (such as using the brake to keep from speeding up to much), the engine just dies.



Now, I'm not talking about lugging it down way below idle or anything, just near idle. It's really annoying, especially if it's icy, then the surge spins the back tires and things get really fun!



I've driven LOTS of different diesel trucks and never had one behave like this. My old '98 12V just goes on it's merry way, even if you really do lug it down to, say, around 400-500 RPM. It just chugs along and eventually gets back up to idle. The electronic injected CAT 3406E in my Pete is pretty much the same, none of this sudden surge if the speed gets a bit low.



So, has anyone else experienced this with their trucks? Is this just normal behavior for the newer Cummins 5. 9? If so, I'll just have to remember to keep my RPMs up a bit higher.



-cj
 
Sounds like my '06 is similar. It doesn't want to be under 1000 rpm and will dose itself with some fuel to keep the rpms up. Anything 1000 rpm or above and it is fine, so I just drop a gear and it lugs along with no issues.
 
BHolm is mostly right - the computer will fuel the engine to keep a minimum of 800 rpm. It is a little disconcerting to have it leap forward when the rpms get down to the 800 range.
 
Yep, that sounds like what it's doing. I guess it's "normal" then.

Unfortunately, unlike my old 12V, where it adds fuel to try to maintain idle, these seem to over-fuel to increase RPM. The behavior of just killing the engine if the RPMs don't come up is a bit annoying as well.

I'm sure I can get used to it...

-cj
 
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