what's Lambda Control unit

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.

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/bsmotor/dyser/dyser.bsp?trykk=2.5&af=12.0&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.

http://www.land-and-sea.com/images/dyno/dyno-max/dyno-max_900_hp_animation.gif

[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]

just replace sensors -then it will correct itself.

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.

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

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

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?

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 ! !

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.

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?

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

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...

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

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

i sprayed carb cleaner all around and i cant find an air leak and i changed the o2 sensors and their fine and im not sure what else to check for

i sprayed carb cleaner all around and i cant find an air leak and i changed the o2 sensors and their fine and im not sure what else to check for
Hi Lads , I've been suffering the same sort of problems on my 540,
I replaced both Oxy sensors But no good I noticed that it was worse in colder weather, its turned out to be the Air MASS SENSOR ,all cured

I've got the same problem with my 95 540. We've replaced everything suggested and checked for leaks. No luck.

It is now over at the supposed experts on this kind of thing. The are saying the problem might be dirty hydrolic valve lifters.

According to them if they get dirty the oil can't get in very well until the car warms up and this throws the timing off just enough to cause the problem. They swear that its fixed other cars and are trying to clean mine by flushing stuff throw before suggesting replacement.

It would be nice if there was a way to confirm the problem rather than just replace them if cleaning doesn't help. Anyone know of a way?

A search of the various forums suggests that and enormous number of owners of this model have the problem, yet the BMW dealers seem completely clueless and BMW doesn't seem to be assisting them in getting educated (that latter according to the service manager at my local dealer).

Any other suggestions beyond the Mass Air Flow or vacuum would be appreciated also.

Thanks.

I haven't been on in quite a while. If anyone's still interested in these "continuing" M60 running problems, I 'll come back for a bit if there's posted interest.

I would sure be interested.

The car has been down at what is supposed to be the best independent BMW shop in town and they have gone done all the things they usually suspect with this problem (same as listed her by people) plus one more (dirty valve on the hydrolic lifters so they collapse). It hasn't been any of those.

Currently they are talking to BMWNA to see if they have any ideas so currently we are just scratchin our heads.

These guys are pretty good and so far have fixed ever other car that has presented with this problem, including quite a few that the dealers have just given up on but mine is proving to be even more difficult.

Any help would be appreciated very much

Steve

Hi Steve, your problem seems interesting and these can be tough to pin point in this manner, SO, please list EXACTLY what's been done so far.

Please make it as complete as possible (parts only).

i.e...."everything" doesn't help and it's UNLIKELY the lash compensators are a problem, not on M60's, early M54's sometimes under the right perameters.

talk to you soon, jeff b.

Jeff ,I thought my problem had gone but it seems to go after a reset then it appears 3 days later,heres a list so far

So Far I have replaced The Battery£126, Oxygen sensors £96,The Radiator £275, The LPg valves & filters wet & dry £89,the water Temp sender £7, the ECT £13 ,The Air Mass sensor (S\hand £99, the spark plugs £22, The coil Packs checked £36, the rubber stubbs on C\Packs £59.60, The Alternator Re-con £186, the Drive Belt £ 15, 3 Diagnostic checks £115 2 rear Tyres as I was told they had flat spots £247 as you see I've spent a bit but you can add £ 100 for all the time & running around & days off, so what next ??

It has been on 4 seperate diagnostic machines each time after I've replaced a sensor etc but it keeps coming back as Oxygen sensor I have 4 IN THE BOOT & 2 NEW ONES IN THE CAR yesterday I took it to a place they had it on there machine for 40 minutes & they came out & said its not the ECU but they cannot help me & no charge...what in the hell is it & its obviously a very common problem on 540's??

Hi everyone, my e39 523i which is a 96 on a (p) with 96,000 miles, has a rough idle its slight when cold and more notacble when at temp, it hasnt affected the car that much its just more of a annoyance really, i have posted on various sites to see if some one can shed some light but as a few have said it could be anything i noticed that the car's perfect if i disconnected the air flow mass meter and wonderd if this was the problem i was then told to go to the main dealer for diagnostics test so of i went i ended up walking away disgusted as i was there for forty minutes and no one came to see me, so i took it to a guy i used to work for when i left school and he did the test there and then and found four faults from the air flow mass meter to the lambda probe but explained that one fault could cause all so he cleared all the faults and told me to run it and go back next week for another test to see what comes up in way of a fault and hopefully it will be sorted, ill update if the car is fixed

Incedently i have bought a air flow mass meter (just in case) second hand with a 90 day guarantee for £57.57p including v.a.t. and postage through The Parts Gateway and from Quarry Motors in Sheffield (01142) 755916 the cheapest i have found.

Jeff,

Thanks so much for your offer to take a look. My situation is very similiar to yoyo1.

The block was replaced with alusil engine about 6 years ago.

Here is some test data on the car

Here are the compression and leak down readings from your car:

compression was 185-190 psi all cylinders (test was done on 2 separate occasions)
leak down was 3% to 7%
vacuum at idle was 19"
TPS .62v
exhaust backpressure less than 1psi @ 3000rpm


Here is what has been done to date that I remember

Spark plugs of course
Tested the coil etc
Replaced the airflow meters Replaced the coolant temperature sensor Replaced the intake manifold sensors Cleaned and rebuilt the fuel injectors (twice)
Check and confirm good strong operation of the fuel pump (at least when at the shop)

I know the gasket on the top of the manifold was replaced, twice and it and all vacuum lines checked for leaks.

The air box was replaced (not sure this is correct term. item in lieu of PCV) and the oil separater.

The first shop just gave up so I went to who are supposed to be the local BMW gods. The thought it might be the lifters. Chemically cleaned them and the noise went away but no improvement.

So they supected the air box/pcv (because something didn't happen when the dip stick removed. Can't remember if idle was or was not supposed to change) and they replaced that a second time and problem is supposed to have gotten better.

However I went to drive the car and it still has a long flat spot with low power when you push the gas and an intermittent single backfire (once per day at startup, but not always). So they are replacing the throttle position sensor or something).

BMW is claiming its bad gas. Local BMW dealership claims dirty valves (but mine have been cleaned twide). Current shop seems more competent and considered but still no one is sure what is going on.

Clearly these engines have an endemic problem given the number of owners out there experiencing the same symtoms and the same inability even after repeated visits to the shop to find it.

If only BMW would get involved.

So any advise would be appreciated.

Took mine to a A\Electrician today, he says that he feels its a airleak, this is because there is no engine check light lighting up so its not electrical.

I shall reply by the weekend...............jeff b.

Right found out Exactly what the problem was on my car, it was the wiring leading to the Injectors.

One cylinder was firing intermittantly, when it got hot the connection got better.

The wires for these are in the plastics trays on top of the Rocker box, undo the box ,they unclick , then press all the wires fully home to make sure they have not worked lose with vibration over the years.
Also take out the ecu's Abs units in the E-Box & check all the earth connections are not loose or corrodede etc.

Mines running like silk now at last!

I've got the same prob. with my 94 530i i'll try your solution, but what's the 'rocker box?' are you talking about the wiring on each cylinder bank?

Gentelman,
Im with u, I had the same problem and i have solved it for 80$ !!
it was my fuel pump. The one that sits in the tank. Yes, that one. I was crossing San mateo Bridge at night (In Nortern Cali), and the car just died in the middle of the bridge. Check engine light came on, car "switched" to what felt like 2 cyl mode, and I had to perform emergency landing in one ov those "safety pockets". I ran stump test, blinking light showed Os sensor fault, then I leaned down to take l look under the car, and I saw exhaust pipe glowing red. it was so hot.
Faulty fuel pump was messing the things up, because when i sprayed fuel into intake colector car started running perfectlly.
Try this web site http://car-part.com/ to search for used fuel pump (new is like 320-350 $), I found mine frim 95 740 for 80$, replaced it myself, took me 1/5 hr, and the problem is solved!!!
Good luck

I've got the same prob. with my 94 530i i'll try your solution, but what's the 'rocker box?' are you talking about the wiring on each cylinder bank?


Anybody seen Jeff...............

I am not sure if this is realted but I am installing something that not many people know about. A hydrogen Booster. A Lambda Controll is nessacary for one of these units to be on a fuel injected vehicle with an O2 sensor. Please see: http://www.brownsgas.com/hydrogenturboboost.html for more details. What does the unit do? My best guess allows the vehicle to know some type of mod has been made then the onboard pc makes proper adjustments to compensate for the O2 sensor. I will be the first to say I know nothing about vehicles but learn daily as they are changing daily.

Oh a Hydrogen Booster allows a vehicle to use an alternate fuel source. Water. The Hydro booster seperates water molicules H20 into a gas form through the intake and increases fuel usage and mileage. not to metion the added horse power.