M3 blowing black smoke!?!

[BMW325issport]

People behind me say when I accelerate hard I blow black smoke out the exhaust. Does that mean it's running rich or bad cat or both or something else? Any input would be great. Thanks

[flyfishvt]

Running rich. Your gas mileage must suck

[BMW325issport]

Gets 25 mpg according to the computer

[UnderCoverGuy11]

You should manually check it, fill it up and reset the trip counter, next time you go fill up divide miles by gallons of gas it takes to fill up again.

Anyways, check your oil level, you might be burning oil

[BMW325issport]

replaced the oil separator and it dosent burn a drop of oil. n plus oil smoke is blueish white so idt black smoke would be oil.

[Eric93se]

Also replace the two hoses on the oil separator.

What weight oil are you using?

[DStein]

Is your engine running cold? T-stat problem/poor combustion?

[snaponbob]

Not the cat, and not oil if the smoke is actually black and consumption is low. Any mods or tune? When was the last time you checked your air filter ?!?!?!

[BMW325issport]

Running 0w-40 stock new vacuum lines and practically everything under the manifold. Plugs are kinda old. Could the maf cause this?

[sjpgoalie]

Running 0w-40 stock new vacuum lines and practically everything under the manifold. Plugs are kinda old. Could the maf cause this?

Yes. If it is dead, you will run on the rich side by default in an open loop mode to protect the motor. Same with o2s. They usually cause a rich condition if an o2s fails. If they detect lean conditions, they're still working, obviously. But, yes. A bad maf could cause it. Get one at a junk yard or a dealer. Do not buy one off the internet or from a parts store. It will be a generic part and these do not like generic MAFs. Many a people have spent many a money buying generic MAFs that disagreed with the DME. It is a big rule of thumb. Same goes for the cam and crank sensors.

[BMW325issport]

Yes. If it is dead, you will run on the rich side by default in an open loop mode to protect the motor. Same with o2s. They usually cause a rich condition if an o2s fails. If they detect lean conditions, they're still working, obviously. But, yes. A bad maf could cause it. Get one at a junk yard or a dealer. Do not buy one off the internet or from a parts store. It will be a generic part and these do not like generic MAFs. Many a people have spent many a money buying generic MAFs that disagreed with the DME. It is a big rule of thumb. Same goes for the cam and crank sensors.

Wouldn't it running in open loop cause the check engine light to come on? Or they could be slowly on there way out. And I'm planning to do the 803 bosh maf with trm tune so if it is bad ill defiantly go that way

[sjpgoalie]

Wouldn't it running in open loop cause the check engine light to come on? Or they could be slowly on there way out. And I'm planning to do the 803 bosh maf with trm tune so if it is bad ill defiantly go that way

Running rich in general should set it off if it is a prolonged/recurring thing. Are you sure you're running rich? Because there have been times where I had oil and carbon in the exhaust and it would bellow a big black cloud out and would continue smoking out the exhaust if I shut it off afterwards. I'd realised that it was merely oil and carbon that had caked up in the exhaust and it was burning off/blowing out. Are you losing oil? I noticed this happened after pussy-footed her around for a while and didn't drive her hard enough. Do you do a lot of city driving? If your CEL is not on, it is probably something simple and stupid. I'll keep thinking about it. Have you ever run too much oil at some point? And does it blow out smoke every time you get on it up high in the rpms? Any where else in the band?

[BMW325issport]

Running rich in general should set it off if it is a prolonged/recurring thing. Are you sure you're running rich? Because there have been times where I had oil and carbon in the exhaust and it would bellow a big black cloud out and would continue smoking out the exhaust if I shut it off afterwards. I'd realised that it was merely oil and carbon that had caked up in the exhaust and it was burning off/blowing out. Are you losing oil? I noticed this happened after pussy-footed her around for a while and didn't drive her hard enough. Do you do a lot of city driving? If your CEL is not on, it is probably something simple and stupid. I'll keep thinking about it. Have you ever run too much oil at some point? And does it blow out smoke every time you get on it up high in the rpms? Any where else in the band?

It burnt alot of oil before I replaced everything under the manifold. Now it dosent burn any but I do have the oil about half a inch above the full mark but I wouldn't think that would harm anything. I open her up occasionally once she's fully warmed up I'm not afraid to get the revs up so there shouldn't be too much build up In it. Also when the temp outside is warm it dosent pull as hard in lower rpms and I notice when I go behind it it sounds and feels like the exhaust isint flowing right. It puffs makes it sound like it's missing. My other e36 did that and I suspected it had clogged up cats as it would do exactly that and barely move when hot but it would fly when the weather cooled down. Do you think the cats could be becoming clogged? Or do all e36 puff like that at idle? Personally I don't think it should.

[Eric93se]

half inch over full mark is way too much. And yes it is bad because the engine can foam that oil and you can blow your motor.

[BMW325issport]

I did an oil change today and corrected it. I put aittle over because it was burning it and I didn't think it would last long but after the osv was changed it stopped burning it and the level remained the same

[sjpgoalie]

half inch over full mark is way too much. And yes it is bad because the engine can foam that oil and you can blow your motor.

Half an inch should put you up around the number 7 on the dipstick, which is eight quarts. As long as you can still see the numbers, you'll be ok. S52 pans will hold up to ten quarts. It will cough excess up into the intake before it bubbles and cavitates.