scantool readings - The Unofficial BMW M5 Messageboard (m5board.com)

max95se · 29th May 2006, 09:44

HI all. I'm a bit confused from these readings I got from my car. I just picked up an autoenginuity scan tool and
this is what I got this evening when I took
a cruise to a friend's house. Anybody else in the board who has this scan tool
and help me interpret the data I got? Thanks in advance!
The next step would be to change out the mafs I received as well.
are my current values ok? I have this problem where the rpm would hunt
when starting in the morning. Basically, the data has the 2 pre-cat 02 sensors, rpm, intake temp and maf air flow rate. the car is running on 6th gear on the highway.

thanks!

Tozzy · 29th May 2006, 11:16

Your O2 readings are nice and even between the 2 sides, the MAF value looks like you were cruising with not much pedal applied.
After I cleaned my MAF's I got 30 lb/min at WOT on 2'rd just before the revlimiter, before the cleaning I only got 25 lb/min. It will only show the max values for a short while so record several WOT runs to the revlimiter and see what max values you get. The 5lb difference made a BIG difference, specially when starting with a cold engine but also in the smoothness and power during acceleration. Most of the engine hesitation during warmup and hard acceleration is gone now.

Not sure what the O2 values should be but my values are not as close to each other as your figures, I usually get maybe 0.2 on one side and 0.7 on the other, have a feeling these values should be about the same on both sides..

bmwdctr · 30th May 2006, 03:11

Couldn't get a bigger picture?

Seriously, there's not much info here. O2 sensors appear to be in closed loop, assuming they're fluctuating from around .2v-.8v. The rear O2's should be a steady referrence voltage of around .5v.

"I have this problem where the rpm would hunt when starting in the morning."

If you already have the MAFS, go ahead and change 'em. They're cheap and easy. Then start the car tomorrow morning. You may notice a difference right away.

max95se · 30th May 2006, 22:19

sorry for the small pic. I got more data and it seems like
one of the front 02 sensor does not fluctuate that much
compare to the the other side. The B1S1 goes between .1 to .81 volts
but the other one goes from .73 to .78 volts only. I guess one the sensors
is stucked and needs replacement? I've installed the new Mafs and it still
hunts in the morning but it runs better. I wonder if this 02 sensor has
something to do with it. Thanks for your help. I The data is based on
the car running on 6th gear @ 2350 rpm (66mph).

thanks.

bmwdctr · 30th May 2006, 22:45

I was just kidding about gettting a bigger picture, the one you had was big enough

"The B1S1 goes between .1 to .81 volts
but the other one goes from .73 to .78 volts only."

B1S1= Bank 1 Sensor 1. Bank 1 is the right bank (passenger side). Sensor 1 is forward of the catalytic convertor. By "the other one", do you mean B2S1? If so, you may have a vacuum leak, causing the O2 sensors to drive the system rich. On the other hand, the sensor itself may be faulty.

I think you may be in over your head and without seeing you car I may be steering you wrong. Now's the time to seek professional help

max95se · 31st May 2006, 00:28

thanks... will get expert help - dealer. haha.

DavidS · 2nd June 2006, 01:32

Quote:

Originally Posted by max95se

sorry for the small pic. I got more data and it seems like
one of the front 02 sensor does not fluctuate that much
compare to the the other side. The B1S1 goes between .1 to .81 volts
but the other one goes from .73 to .78 volts only. I guess one the sensors
is stucked and needs replacement? I've installed the new Mafs and it still
hunts in the morning but it runs better. I wonder if this 02 sensor has
something to do with it. Thanks for your help. I The data is based on
the car running on 6th gear @ 2350 rpm (66mph).

thanks.

A bad pre-cat O2 sensor could definitively be the source of the problem you described.

David

max95se · 2nd June 2006, 10:11

sounds good. thanks david. i need to schedule a visit to the dealer.