Code 0A on both banks, rough idle to warm/ high rpm

[cle750]

89' 750il - recently cleaned throttles, mafs, reset throttles 2 weeks ago

A couple of days ago when I started the car is was running really rough and with no power (rpms where not limited to 1500, didn't seem like limp mode) I ran the scan tool and got code 0A on both ECU's. Once the car warmed up/ i took it for a spin and hit decently high rpms in first the light check engine light went off and the car ran great, power was restored. Everytime I start the car this happens now until I drive around the block/ hit high RPMS I have no power. Could this be electrical light alternator/ battery or should I just replace both 02's? Reason I ask about electrical is that I recently have heard noise/ a squeak from my alternator on startup sometimes.

also being as that it goes away and then the car runs good it makes me believe it is not a vacuum leak or anything "broken" completely. Seems like something is warming up then it runs fine. Car has 184,000 miles- 0'2's look old. battery is a few years old. Alternator is also of un known age. When I think back this problem arose after I washed the car. I washed the car, went back in my house and left again 10 mins later and the problem started. I have drove the car 10 times since and it does it every time.

[shogun]

first of all check the voltage. 750 are very sensitive on low voltage. You can unlock the OBC and on #9 you can see actual voltage. When voltage is too low, all modules are confused and not even the engine controls have probs but also the IHKA unit, electric seat module/switches etc.

Which code tool did you use? Peake?
OA = Coolant Temperature Sensor
Check the coolant temperature sensor on the back of the engine in the coolant pipe. Maybe slipped of plug?
There are 3 plugs. See Bentley repair manual or www.realoem.com

Also do a stomp test, see my website below.

Also on the rear of the engine close to fiewall on the intakes on each side there are 2 air temp sensors. Sometimes they slip off (plug) when not good installed.

[cle750]

Yes I used a peak tool. My peake book says it is the lambda control. Took it for a drive tonight and it seems like it takes longer to "go away" than it was before.

[shogun]

I have my doubts with the lambda control. You can disconnect the oxy sensors under the car and drive with oxy sensors for a test, under this condition the motronic will take a default value = runs richer. Before you disconnect the oxy sensors, mark the connections, easy to mix the connectors of 1 and 2 and then the engine runs terrible.
You can also measure the oxygen sensors with a volt meter on the Motronic, remove the connector, remove the cover on top then connect again and you can measure like this
http://img293.imageshack.us/img293/5...onik005tm0.jpg
http://img167.imageshack.us/img167/2...onik001zi7.jpg
normally it looks like this, pic from my parts car
http://imageshack.us/photo/my-images...engine0jo.jpg/
http://i71.photobucket.com/albums/i1...xopenclose.jpg
pinout
http://www.e38.org/e32/750ilpinout1988_90.pdf
Pin 23 Oxygen Heater RelayControl

Pin 28 Oxygen Sensor Signal

on the 156 Motronic like yours
Pin 28 (+) und Pin 10 (-)

cable colour accdg to Bentley Book ELE-72

Pin 28: Schwarz/black
Pin 10: Gelb/yellow

Lambda control can mean many things, they are either dead or report values which are not conform but the problem is then ahead such air, faulse air, air temp, MAF etc.

[cle750]

Yeah we have had bad weather here today so I did not get to take a look at it yet but I did drive the car again last night and the problem seemed to be getting worse. So whatever it is something seems like it is failing. I had a few issues getting the OBC test 9 to run. I think I am hitting the wrong button after I pull up test 9. What is the proper procedure again? Thanks shogun, you really are the 750 master.

Also would any one happen to know what color wires goes to what part of the sensor on the right side of the radiator? i believe this is the fan control? mine have always been disconnected and loose.

I am seeing 13.68-13.5 volts at the obc test. It never goes over 13.7... Think its voltage regulator time?

[shogun]

you mean the aux fan control? Right side of the radiator?
Here
http://www.nmia.com/~dgnrg/page_20.htm
http://www.bmw4life.com/auxFanR.htm

13.68-13.5 at the OBC is fine for an 750. That would be normal. But if the regulator has never been changed, might also be time for that on next occassion.

After you pushed # 9 test, push the set button on the right side of the OBC.

[cle750]

Yes I got that reading on voltage from the obc 9 test. Remembered the sequence. It did fall as low as 13.4 while idling.

[mottati]

what would be considered too low for voltage? I have a new check engine light, can't get stomp test to work. Engine off voltage using test 9 is 11.7, idling 12.3. Is that ok, battery is about 6 years old.

[shogun]

since I changed my wire from alternator to B+, I get wonderful voltages
http://twrite.org/shogunnew/fixes/electricalpower.html

before the OBC never showed a 12 or 12, mostly 11.xx

I will never forget what a real expert told me back in in 2004:
quote

Low voltage will set EML only if it drops below 11V for more than 90sec.

Low voltage will also cause problems with the IKHA (heater/ac), memory for seats/steering and transmission will go into limp mode.

Mismatched tires WILL set EML light if vehicle has traction since it reads all 4 wheel speed sensors and gets an "implausable" reading.

Just for clarification: I am a 20 year BMW Master with 3 PhD's from Germany in Engineering and I know these systems better than almost anyone. I did 12 years of R&D on these system for a manufactorer in Germany, so I am not some "Key Board" mechanic or read some crap on the internet.
Ronald Trochelmann
Performing Imports
www.performingimports.com

unquote

[cle750]

I replaced my plugs, wires, checked all the coolant sensors. Now the car has no power at all, even when warm. Still throwing code 0A (lambda). Now i did notice if I unplug the passenger side MAF the engine dies instantly. If i plug or unplug the drivers side MAF it makes no difference. I am guessing this MAF is bad. Any suggestions on replacement?

Also, I tried cleaning the MAF twice with the proper cleaner. This MAF (the one I can disconnect with not difference) looks older than the other and is not a bosch from appearance.

Ok I did some more testing and found that the side of the engine corresponding to the Maf that seems to have no influence on the running for the the motor is cold at the exhaust so therefore must not be running. I found the connector (3 pins) on the front of the motor to be bad. It is the connector that sits above the one from the plug 6 sensor. It has the same connector type as the sensor on the plug wires. The outer shielding connection (ground?) Of this wire /connector is torn. The engine has no effect if I run it with or with out it plugged in. I am going to have to repair this. Can I carefully splice the connector from a old plug sensor? They look the same. Would this make this side of the engine not run? Otherwise I am pointing to the possible fuel issue. I found a post where there was a car with similar symptoms and it had a fuel pump problem, never threw a eml and sometimes a check engine light with both banks codes for lambda control. Same problem as mine. I was told both pumps were replaced on the car before I bought it. Any easy tests besides just pulling the lines? I am thinking maybe I am not getting fuel on this side?

The Maf tested at 2.4 volts at idle steady on pin 6. I think it may be ok.