E60 M5 - constant speed misfire?

E60 M5 - constant speed misfire?

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Tony B2

Original Poster:

610 posts

174 months

Monday 1st September 2014
quotequote all
Raising this question on behalf of a friend, who has a 2007 E60 M5.

He has owned it from new, covering 27k miles so far. No expense spared on servicing, and it is still under (extended) warranty.

His words:

"I have the following issue which is not being logged by the engine management system as a fault.
With engine running at fixed rpm anywhere between 3400-3600 rpm there is a slight "splutter" in the exhaust note every 1 to 2 seconds. If I hold constant rpm outside this range the exhaust note is constant."

My words:
I have heard/felt this for myself, and stood behind the car whilst he holds the revs mentioned. I can hear a quite distinct "woofley" sound from the exhausts, randomly from left or right exhaust pair.

The car seems to be down on power at the top end, as it was slow to exceed an indicated 160mph (autobahn of course) whereas normally it would run up to an indicated 180mph quite quickly.

It will be in the dealer's tomorrow, but they seem to be pretty incompetent in diagnosis, so any ideas gratefully received!

AW10

4,422 posts

248 months

Tuesday 2nd September 2014
quotequote all
He says no faults are logged. Is this statement based on no check engine light, reading the (lack of) codes via generic OBD software or reading the (lack of) codes with BMW specific SW? If his answer is anything other than the last choice then that's what he needs to de - use BMW specific SW.

Tony B2

Original Poster:

610 posts

174 months

Tuesday 2nd September 2014
quotequote all
No faults detected via the dealer scan

jcolley

183 posts

125 months

Tuesday 2nd September 2014
quotequote all
Datalogging can be useful here.

There's a freeware version of BMWLogger2 as well as one called "testo" (google "testo bmw") and look at ignition pulsewidth, injector pulsewidth, etc.

Also, INPA can be used for live sensor logging to help identify the cause. Look for variations in MAF flow, throttle actuator position, idle actuator position and Lambda values (AFR).

I have had a similar problem on mine since I bought it that has led to replacing all coils, fuel filter, carbon cannister, all spark plugs, MAFs, air filters, all to no avail. Recent logging indicates that the Lambda target value of 1.0 can't quite be attained and the injector pulse-width is being modulated up and down consistent with the up and down of AFR and the 'surging' feeling on very light, constant throttle driving around 3500RPM. I'm still trying to work out why the DME can't just choose a pulse-width in between the two it is and be done with it.

Tony B2

Original Poster:

610 posts

174 months

Wednesday 3rd September 2014
quotequote all
First feedback from the dealer is "check the air flow meters"....

Which will happen today. Tomorrow's check has not yet been identified, but I have a feeling that this could take some time...

jcolley

183 posts

125 months

Tuesday 28th October 2014
quotequote all
Tony B2 said:
First feedback from the dealer is "check the air flow meters"....

Which will happen today. Tomorrow's check has not yet been identified, but I have a feeling that this could take some time...
Any luck resolving this?