BMW M5 Forum and M6 Forums banner
1 - 8 of 8 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 · (Edited)
Hi All,

Another question for the M5 gurus - Ive just followed a mate of mine driving the Touring and its apparent theres too much smoke. Its black/grey and is present in wisps when you pull away - and when booting it, quite a cloud is left. Its clear most of the time, just certain pull aways gave some wispy smoke and quite a big cloud when booting it.

Emissions were high at the MOT and the plugs black when changed last w//e.

Is this a Lambda issue, or somthing else? If I take it to BMW/Specialisy can they tell me whats wrong with it by using the diag machine?

Thanks
Paul
 

·
Registered
Joined
·
1,338 Posts
Paul

A pal of mine who works at an ///M specialist explained that they sometimes struggle to get our cars through the MOT emissions test, and apparently they always conduct the test at a cold start because the air pump leans out the emissions particularly well!!

Mine produces some smoke when you hoof it, especially visible at night in the headlights of a following car.

As an aside, I'm working away this week and next week. I believe I'm not a million miles away from you. If you fancy a compare/contrast then just give me a shout.

Cheers,
Andy
 

·
Moderator Emeritus
Joined
·
4,273 Posts
toxicfrog said:
Hi All,

Another question for the M5 gurus - Ive just followed a mate of mine driving the Touring and its apparent theres too much smoke. Its black/grey and is present in wisps when you pull away - and when booting it, quite a cloud is left. Its clear most of the time, just certain pull aways gave some wispy smoke and quite a big cloud when booting it.

Emissions were high at the MOT and the plugs black when changed last w//e.

Is this a Lambda issue, or somthing else? If I take it to BMW/Specialisy can they tell me whats wrong with it by using the diag machine?

Thanks
Paul
Paul
Iam as far from a Guru as you could probably get but heres my 2pence worth.

If its the o2 sensor, it will show up on the fault code readout.
Sometimes, its the plug & wiring to the sensor & you can clear the fault from the DME , wiggle the wire & the fault will be cleared & the car will run as normal for a while with out the enriched mixture.
If its the o2 sensor the fault code will re-occur straight after it has been cleared & the engine restarted.

It could also be a faulty water temp sensor telling the DME that the coolant is cold & to fuel for a cold start.

It could be a MAF sensor going awol.

It could be one or more of the coil packs coolant gell pack staring to break up giving intermittant spark.

You state that it was giving high emissions. What where the percentages for HC @ Idle & fast idle (about 2500 rpm)

Theres a lot it could be & without being there as it where, This is only a little guide but from my past experience I would not rule any one of the above out.

Andy mentioned the air pump & a cold start.
The air pump is not always consistant on start up (a lot to do with individual throttle intakes)& was designed to aid in an aggressive cold start strategy to get the catalyst monoliths up above 400 degrees exhaust temp at which point, the catalysation process will be efficient. Below 250 degrees, or a cold engine you get no catalysation & a lot of fuel in the system.
I cant see how a cold start will help when this is reqd & oil temp has to be above 80 degrees C also.

Regards
Farrell
 

·
Registered
Joined
·
1,338 Posts
farrell said:
The air pump is not always consistant on start up (a lot to do with individual throttle intakes)& was designed to aid in an aggressive cold start strategy to get the catalyst monoliths up above 400 degrees exhaust temp at which point, the catalysation process will be efficient. Below 250 degrees, or a cold engine you get no catalysation & a lot of fuel in the system.
I cant see how a cold start will help when this is reqd & oil temp has to be above 80 degrees C also.
That's a very interesting point!.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #6 ·
I took the car down for another emissions test this morning at my MOT place and it passed everything first time.....Im highly confused!

Im going to change the temp sensor and leave it at that I think as this is what several people have told me to do.

Thanks
Paul
 

·
Registered
Joined
·
178 Posts
toxicfrog said:
I took the car down for another emissions test this morning at my MOT place and it passed everything first time.....Im highly confused!
Hi Paul
My car didn't pass the Swedish emissions test during its first import inspection. They measure CO, CO at 2500 RPM, HC and the Lambda value (calculated). The lambda value was fine, the rest too high. The car had then been running for a couple of minutes including a short testdrive around the block.

It turned out that this was a common problem among ///M owners on a Swedish BMW forum. BMW's in general, and particularly the M models, require a good warm up to get the catalysers at operating temperature.

I took my car to the local BMW garage to double-check the emissions, since it had passed the test in Germany and I thought it was running well. They took it for a 5-10 min drive on the highway with the oil above 80°C, keeping the RPM around 3-4k all the time. After that, the emissions were very good and it passed the test without any fixes. So before changing spark plugs, lambdas etc, make sure the car is properly warmed up when doing the emissions test!

Thought this explanation could apply to you as well.
 

·
Registered
Joined
·
125 Posts
toxicfrog<SCRIPT type=text/javascript> vbmenu_register("postmenu_559428", true); </SCRIPT>

Hi. I have a same problem. I tried a following: when the motor and the oil fully warmed. 30minute hard driving. Disconnect the dme ...wait a minute and connect. Start the car. Now the engine and the lambda sensor hot and the dme begin to learn the setting in warm position. The smoke disapered. And the consumption fall down from 20liter to 14 liter. The idle smooth...so a lot of crazy thing ended. Now everithing run fine.

Try it.

Maybe it will help.

Sorry my english is not "over the top". I am from Hungary.


Frank
 
1 - 8 of 8 Posts
Top