what's Lambda Control unit

[shon]

hi,

I'm getting a 'Lambda control unit #1' code on my 1995 BMW 540iA. The car runs very poor when cold. The engine acts like it's missing and the check engine light comes on. I'm getting the 'lambda code plus O2 sensor #1 & #2. after 15 minutes of driving the engine smooths out and the check engine light goes out.

I know for a fact that if O2 is bad, then it's bad. it can't go off and on. that's why I was asking about this Lambda unit since I've never heard of it. Also would anyone think this may have to do with 'air flow meter'???

thanks for any suggestion and info.

[KC Ron Carter]

The error message said Lambda plus o2 sensor.

The ECU will list all issues but the o2 sensor replacement will fix both.

Here is a link to explain the BMW fuel control.

Dwell and the Lambda duty cycle on BMWs

Dwell is the name of the output of the ECU to the INJECTORS, Bosch does not recommend monitoring on BMW. It is called dwell because a dwell meter is also a percentage of duty cycle reference.

What is readily available is the output from the o2 sensor that the ECU uses to make its decisions on.

On the later EFI BMW used the 65% design range to size the electric injectors.
Here you can see they used the pulse or dwell as the primary design in sizing injectors.
cc/min Ohms Application cc/min @ 2.5 bar Max. hp with 6 injectors

One is rated at 511 hp with 6 injectors.

http://www.bsmotor.com/cgi-bin/bsmot...&ant=6&pros=65

On the later EFIs you can use a larger injector to provide what any engine modifications have allowed the engine to use.
Having said that the o2 sensor will lower the pulses on the larger injector if not needed to reach the 14.7 to 1 of air fuel mixture.
So just changing injectors is not a performance improvement.
It, the ECU will only what is needed and will leave idle any output not required.

380 cc/min 404 hp is the injector for my big dog. In addition using a Cartech Risng Rate Fuel Pressure Regulator I can increase the 37.5 pressure to 100 psi and the same injectors will make 600 hp.

[Olliem]

[Hello shon,

I'm having the exact same problem, did you get the problem sorted out ? BMW tells me that a short block is required to fix the problem....

Please let me know.

/Ollie]---------------------------------------------------------------------
I'm getting a 'Lambda control unit #1' code on my 1995 BMW 540iA. The car runs very poor when cold. The engine acts like it's missing and the check engine light comes on. I'm getting the 'lambda code plus O2 sensor #1 & #2. after 15 minutes of driving the engine smooths out and the check engine light goes out.

I know for a fact that if O2 is bad, then it's bad. it can't go off and on. that's why I was asking about this Lambda unit since I've never heard of it. Also would anyone think this may have to do with 'air flow meter'???

thanks for any suggestion and info.[/quote]

[mechy1barry]

just replace sensors -then it will correct itself.

[shon]

replaced both O2 sensors, and it still not running right. most the time it runs smooth and great, but when cold, or the first 15-20 minutes the engine shakes and it almost like it's missing a couple of cylinders. Sometimes even when warmed and stopped at a red light it will do this again. but when I get going the check engine light goes off and it runs smooth again. Yesterday I finally dropped it off at the BMW dealer for diagnostics.

[buzz71]

shon,

i realized that it's been awhile since you had this problem. i'm having the exact same problem with my 540i, i also replaced both sensors and the problem is still there. i'm scheduled to have it looked at from an independent bmw shop. can you tell me what they did to resolve your problem.

thanks,
jimmy

[kelminr]

shon or buzz,

I am having this problem with a 1992 325i. Were either of you able to solve the problem? If so what was the diagnosis?

Thanks,
Nate

[kbrown528I]

My 99-528i is going back in friday for the same thing. I have had the fuel lines checked for leaks and ever since I got it back it starts VERY ROUGH!. If anyone lese has had this fixed lets hear how?

[jeffreyb4me]

The most likely cause for the M60 problems mentioned is the Crankcase Pressure control valve on the rear of the intake manifold........reviewsome past posts ! !

[jeffreyb4me]

BY THE WAY, I just completed the troubleshooting on a '94 540i on which a Dealer had actually replaced the shortblock for this same problem......guess what didn't fix......it's a long story so be sure whom ever repairs your car ahs a good idea of what he/she is doing.

[kbrown528I]

My Intake from BMW called me to let me know it was the Crankcase Pressure Control valve. He has had my car since lasr friday and I am not getting it back until at least this Friday. He has to order the part and he says it is a 5 hour job, to your knowledge is that right?

[atv087]

ive never heard of that but my bmw has the same problem and it burns oil and when cold it idles rough and when warm the check engine light comes on

[antose9]

OMG I`m havin the same problem with my 1994 540... I had dealer replace one oxygen sensor, then I replaced the second one myself,and i`m still getting problems... Sometimes "check engine' light comes out in a middle o highway, car looses power and andter a few starts and goes I get it back on the road.... Mistery to me...

[atv087]

yeaa man

lemme know if u ever figure out whats up with it and if i figure out whats wrong with mine ill let you know

[tnabiz528i]

I have the same prob with my car I went to the dealer and was first told it was an oil problem so I had the car flushed and the oil changed several times still happened went back and then was told it was a fuel problem, not that either then I was told o2 prob, nope not that either then I was told short block, mean while thank god bmw was paying for all of this shit, still same prob well now that my warenty is up they tell me it is a bent rod or somthing I hope someone gets the answer soon