Bad running cummins 8.3

[goldsky]

I have a 1999 American Dream Motor home with an 8.3 Cummins ISC caps Engine 133000 miles on it

And it is turning in to an American Nightmare.
Maybe somebody familiar with this Engine has some ideas.
Any help is appreciated.


Engine is loping/hunting on idle, black smoke runs bad and has weird noise coming from muffler. Had a few mechanics advise me what to do, but it not help much. Did a lot of work and replace parts, but it is still doing it.

Here is what I did so far.

Replaced fuel filters, replaced fuel hoses from tank to filters. Checked air filter ,replaced Injectors. Installed Fass lift pump. Replaced high pressure pump with Cummins rebuilt, That made it smoke less, had Injectors that I replaced rechecked, removed timing gear cover checked timing marks, removed and checked Muffler and exhaust brake. Checked Turbo, spins freely, no oil leaks. Replaced Cam sensor and speed sensor. Replace map sensor, pressurized intake from turbo, no excessive leaks. Checked Valve adjustments numerous times does not change, checked compression 400/420.checked exhaust manifold no visible cracks



Check engine was on before I replaced the hp pump, but now no more check engine light.

One mechanic suspected that it was a slapping piston, but with good compression and no blow by, it seems unlikely to me.
Below is a link to the Video.

Below is a link to the Video, Notice funny sound from muffler.

 

[dbarnes]

You might try checking each intake port @ the heads for leaks. Way back when I worked as a Cummins mechanic we had a engine that would lope, run rough at idle and seemingly had a miss. Injector and pump work did not resolve it. We then resorted to spraying starter fluid around each intake port flange.
When the unit picked up speed and smoothed out we knew we had a intake leak. It also smoked at idle.
I have experienced similar issues on Gas engines later and solved them the same way. Very confusing in take the way the engines react to what amounts to lean / rich mix on one cylinder.
Turbo engines or not, a intake leak can be a true pain.

 

[Buly]

Looks like one cylinder is running way too rich, and may not be firing completely? Too much fuel, or not enough air for proper combustion = black smoke from unburned fuel and drop off in the sound.
Years ago on the old Detroit diesels, I used to loosen slightly the injector fuel line one at the time to find the offending cylinder.
But with the new engines, I don’t know if you can do it?
I would be careful with starting fluid for gas engines. It may detonate prematurely if ingested in the cylinder.

 

[dbarnes]

Buly,
True about starter fluid on gas engines, but I didn't use it on gas, only diesel.
Any light oil such as wd40 will combust without the violent nature of starting fluid, but much of the time it simply acts to block the leak long enough to identify the location, plus it evaporates off well. The trick is to get something that won't necessarily cause a fire either. Even the propellant of the aerosol is important to think about. Sometimes it is butane!
Since Goldsky was talking Cummins I wasn't going into specifics on gas.
DB

 

[cycleguy1979]

Did you ever get this sorted out? I just joined today 4/17/22 and saw your post. I have seen two diesel engines do this with my own eyes. Here's what it was on both.
First one was a 2003 Kenworth with a 450 Cummins under the hood. This was in 2007. It started running rough and had no power. Tons of black smoke like a tractor pull would have. Idling it loped just like that. Ended up being a stuck wastegate on the turbo.

The second one was more recent. On my 99 Holiday Rambler endeavor, with the 5.9 cummins 275HP. Had a head gasket on the way out, so we took the head off and got it rebuilt. The ECM on mine bolts to the side of the engine where oil leaks get it covered pretty quick. Anyhow, did the top end rebuild and got it ready to fire. Wouldn't fire at all. Turns out, when I replaced the VP44 high pressure injection pump, I had it timed one tooth off.

So I changed that and put it back together. I did get it to fire up, but it sounded bad. Same as yours. The throttle almost did nothing. Turns out, just unbolting the ECM and setting it off to the side was enough to screw it up and require a replacement from Cummins. This part cost me $2800 plus labor after I threw my hands up and sent it to the freightliner dealer. The injection pump ($2800) and ECM both had to be replaced. Hope this helps someone.