Strong exhaust fumes smell SOLVED

[635sharknose]

My car is driving very well, but I start to bother with the rather strong exhaust fumes that always hangs around the car when I have driven it. You can smell the fumes everywhere around the car. The car does not smoke (no blue, black or white smoke).
Sometimes it is more than other times, but you always smell it after a drive. It does smell burned, not like petrol.

The car also bucks/jerks a bit at low rpm’s, perhaps this has something to do with the smell too. I think something is wrong with the injectors or the air/petrol supply.

Engine block leaks slightly but not much (about a drop per week), so it is not that a lot of oil leaks on the exhaust.

My car was originally fitted with a catalytic converter, I took it off a while ago and it turned out to be completely empty, I’m not sure if that could perhaps cause the strong smell of exhaust fumes.

Someone a good idea what I can look at best?

[hornhospital]

You found it. That lack of a catalytic converter is the cause. Partially burned hydrocarbons because there's no catalyst to complete the combustion.

[plip1953]

You found it. That lack of a catalytic converter is the cause. Partially burned hydrocarbons because there's no catalyst to complete the combustion.

But many/most 6ers supplied into the European market didn't have a cat, but I would never have said I've found exhaust smells to be especially noticeable.

Paul - have you checked the exhaust gasket? That's about the only think my car has ever needed in terms of anything related to the engine.

[hornhospital]

Yours was designed and tuned to run a catalytic converter, the Euro models weren't.

[635sharknose]

Thanks for your comments guys!

I think it would be a good idea to give it a try with a new catalytic converter. Also because of the fact that the car now emits much more than necessary.
There is now a Magnaflow under my car (see photo below), as mentioned, it is completely empty.
The same model is still available, MagnaFlow Universal Federal Catalytic Converter 94007.

Do you guys perhaps have a better alternative than the Magnaflow?

My car is from California, I see that there are other (CARB) catalysts to be mounted in that state. However, it is unclear to me what the difference is. I assume that a “federal” catalyst also works, right?

cat.jpg (175.46 KiB) Viewed 8351 times

[plip1953]

Yours was designed and tuned to run a catalytic converter, the Euro models weren't.

Clearly that's true, but does that also imply that the ecu mapping is different to suit both versions? And if so, can the ecu be re-mapped?

[86_6series]

"The car also bucks/jerks a bit at low rpm’s"

This statement plus strong smell leads me to think it's running rich.

[635sharknose]

Thanks for your response Bob!
I just found that a catalytic converter could break due to a car running rich. That may have been the reason why my catalytic converter broke. It was not completely empty, there was still a loose piece (see photo). To me it shows that a large part of the catalyst has melted down. As I understand now, this may be due to a too rich a mixture.

What is the best method to look for the cause of the rich mixture with the M30 engine?

cat.jpg (273.46 KiB) Viewed 8311 times

[plip1953]

Presumably a cat equipped car has a lambda sensor (whereas non-cat cars of the era, like my own, did not)?

That's where I would first be looking ie is the lambda sensor still connected and/or in good working order. Otherwise I guess I might be thinking it could be a faulty airflow meter.

[635sharknose]

Not a bad idea Phil.
I am sure the lambda sensor is connected. But I'm not sure if it works.
I will take it out an try to test it, same with the air flow meter.
Thanks for the tips!

[635sharknose]

I want to buy a new lambda sensor.
Does anybody know which brand is most suitable to buy?

OEM is € 180,00
There are many alternatives, starting at € 25,00 to € 125,00
Many brands (Bosch, Magneti Marelli, NGK and a lot of unknown brands)

[hornhospital]

Personal preference here, but I've had others with the same experience. Bosch only. The rest may work for a while, or not at all.

And that is no doubt the cause of the rich smell. The Motronic system (and almost all others) default to full rich if the O2 sensor fails. My Jeep Grand Cherokee is doing that right now. Scan it and it says the O2 sensor cannot read the exhaust gasses, and it smells rich (and get HORRIBLE gas mileage).

[635sharknose]

Thanks! Then that is what I will buy.
I must say I had a strong preference towards Bosch already.

Yes, that is most likely what is happening to my car as well! Hope it solves the issue.
That and a new cat.

Thanks

[635sharknose]

The smell is gone!
I exchanged:
- catalytic converter (actually the complete exhaust)
- oxygen sensor
- oil dipstick seals

One of these was causing the smell, which one I'm not sure as I replaced it all at once.

[anchored]

Was definitely the Cat.

I don't have my cat and my car smelled strongly until I went through the effort of eliminating all exhaust leaks.

Still smells, but at least I don't after driving it.

[635sharknose]

Yes, I do recognize that.
I installed a cat of a E32, perhaps that can be an option for you too.
https://bigcoupe.com/phpBB2/viewtopic.php?f=2&t=31538

[anchored]

I actually chopped mine and the resonator to get a bit more clearance. my driveway is weird and my car was high centering.

No problems now and no emissions in my state to worry about.