Niwoj

Also it looks like your initial speculation was correct about the hissing. The brass clamp on the catalytic converter is mildly loose and wisps of smoke come out. It’s pretty hard to get to so it’ll be a couple hour project this Saturday.

Niwoj

Reset the codes and and it hasn’t come back. Today the car started rpm jumping and bouncing in about a 100-200 range and then smoked not only from the back but from under the hood aswell, looked like the Cat region. What are the chances my Cat is clogged. Should I pay to fix it or just sell it and take the loss?

BetterDaze

Hmmm if you are not planning to actually use and keep the car I would not waste anymore time and money. I only kept fighting for mine because it had full service records and I had no other transportation at the time. The money spent you can get a better Benz though this diesel engine should last very long internally not worth it in the short term.

CAT could be clogged but your mechanic should have caught that if they diagnosed the dpf. there is also a collector pipe under the turbo that leaks smoke under hood when cracked(from age/mileage) but I’m not sure since it’s coming out the back too, what color smoke?

Niwoj

I haven’t taken a super good look at the color, under the hood I’d say grey with MAYBE a blueish hue. It smells incredibly acrid though and burns the eyes. Out the exhaust a more blackish color like it’s doing a regen.

BetterDaze

this is how my car was when the collector pipe under the turbo had a crack in it. Smell was very acrid and coming in through my vents visibly


out the back is either old soot coming out of exhaust especially if you really only see a plume under acceleration. If it’s at all times injectors over fueling which increases the car Nox, soot etc.


if the cat was blocked I’d assume you’d also have severe limp mode and maybe trouble even starting, it’d be like coughing

I looked through some old forums and they said to look inside the cat with a light

Niwoj

Only under acceleration ever 3-4 drives. And it never just smokes out the back. It always smokes out the front back right of engine bay (as you look forward as if you were driving) and out the back. I have no idea what it could be, my only thought is maybe a high pressure exhaust leak. The CEL is no longer on either.

BetterDaze

Gotcha, I think you have an exhaust leak somewhere between turbo and dpf and your injectors may be stuck on dirty dpf purge mode.

you can try resetting the lambda but do NOT alter anything asking for injector values nor quantities. You can also try telling the car there is a new NoX sensors or cat….all adaptation options

The old dpf could have skewed those readings, lastly if you have no drivability issues, full throttle on highway to blow that gunk out and if you feel okay maybe drive long enough for it to regenerate then check and see if your scanner will tell you if it actually did one but start with seeing when it last might’ve

No CEL is a good sign but there could be pending codes too you can check for

Niwoj

Only code is a temperature sensor code “correlation” and isn’t throwing a light. I have a good hour and a half of driving tomorrow so I’ll see what I can do about a regen maybe.

Niwoj

Okay, gave her a good couple hours of driving today. New issue, car doesn’t seem to be running rich or smoking which is good. However, on the 45 minute drive to college the car felt pretty gutless, almost like it was in too low of a gear or like no matter how much I depressed the accelerator it would go. 25 minute drive to some errands, car felt snappy, fast, and like how it felt when I bought it, quick acceleration. 20 minute drive home, car felt completely gutless, 0-30 is really fast but then it feels like it’s bogging down, floored in a straight for 20 odd seconds and only got up to 80-85 when typically we could go higher. Thoughts?

BetterDaze

Sounds like limp mode, when the car detects too high pressure in the exhaust system it turns the turbo off and you can still drive but lose all normal power. After you turn the car off and leave it a while, does it seem to forget until you put it back under that same condition? And does it limit you to a specific rpm?

There is either an actual blockage somewhere or a sensor is off-reading. start with the dpf differential pressure sensor and work all the way up to the back pressure sensor next to the turbo. Check inside their ports, clean them and try to reset again.

B28 is the back pressure sensor and sits to the right rear of turbo between it and the EGR. That port can fill with soot and make the car think back pressure is too high triggering limp mode under hard acceleration

Niwoj

I’ll do that this weekend. In the mean time, I’ve found the exhaust leak and source of hissing. The weld upstream where the DPF was welded in is super bad and leaking air and I think smoke when the DPF tries to regen. Could a leak be causing the limp mode aswell?

BetterDaze

Yeah the car needs to sense that back pressure to accelerate properly and a leak right there will prevent a successful regen.

i bet your car is trying to regen like normal your past 3-4 drives and when it initiates you see smoke coming from that leak. It does kinda sit where it can emit both under the car and flow up through the hood

Niwoj

That would make a lot of sense. I’ll try to find the leaky bits and spot weld it this weekend with a buddy.