What would cause an m-11 to just start billowing black smoke and miss at idle and through the whole rpm range?

 

A really bad injector. Or more than one.

It does happen from time to time.

I was working on a kenworth the other day, that has a backfiring problem. Well, turns out it had a couple of injectors hanging hard enough to load the exhaust with fuel residue, and occasionally it would fire off. Loud, like a 10 gauge shotgun.

It exhibited the same symptoms prior to the backfiring beginning.

 

My friend replaced all the injectors and the cam sensor and it still does the same thing. Next step would be ecm replacement?

 

I would see if there is a software update or code present. My dad's had a slight miss occassionaly and they did and ecm update and problem went away. No black smoke on his.

 

What are the boost pressures? Check for bad CAC, was a new fuel pump put on recently?

 

Would low coolant or a bad coolant sensor cause this? The ecm tested good at cummins but it had a coolant code in it. The owner said it would start missing going around corners which makes me think its low on coolant.

 

Is it actually missing as in dropping a cylinder or is it derating from a perceived lack of coolant?

 

Update. Turned out one of the new injectors was faulty. Runs great now. Its still using coolant last I heard but runs good. The slowness is due to the programming. Its rated at 300hp and pulls like my 12v but it does the job.