Emissions problem BMW M3

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Emissions problem BMW M3

Postby trutrail » Sun Jun 15, 2014 7:27 am

We have an issue with a BMW M3 1996 3ltr. The co reading is off the meter (literally) but the odd thing is both O2 sensors work perfectly normal???!!! They oscillate at about 2hz when warm and range between .1 and .9 volts. Any ideas? We were thinking it could be that it is burning oil as the HC reading around 1100ppm. But appart from that I have never seen anything like this.
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Re: Emissions problem BMW M3

Postby HC_CDC » Mon Jun 16, 2014 1:21 pm

I don't know if it the intention of this forum but that will be told by some administrator. Obviously you need an answer quIckly and if you haven't solved the problem yet; you may want to look at a false lean situation, leak in exhaust system upstream or near lambda sensors 1.1 and/or 2.1.. ECU will be enriching because lambda sensor tells it the mixture is lean.

Good luck

Henk
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Re: Emissions problem BMW M3

Postby Robski » Mon Jun 16, 2014 8:53 pm

I don't know if it the intention of this forum but that will be told by some administrator

Any body :?:

They oscillate at about 2hz when warm and range between .1 and .9 volts

What's the cross count ?

We were thinking it could be that it is burning oil as the HC reading around 1100ppm

Misfiring ?

Are any fuel trim values available to you ?
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Re: Emissions problem BMW M3

Postby trutrail » Fri Jun 20, 2014 5:47 am

Thanks for the replies so far. Much appreciated. This car did have a missfire (But if you've ever worked on one you'll know the fault codes and live data for this system are very basic indeed. It did not even recognize a missfire at all!) Thanks god for oscilloscopes we nailed it in 30 seconds and rectified that fault. We will bring it back in and look for an air leak in the exhaust system upstream of the o2 sensors. Cheers so far.
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