Any problems if my Lambda sensor isn't plugged in??

[stevetigger]

Im not putting a CAT system on my M50, so really the quesion is......

Will the car work OK without a Lambda sensor plugged in?


For all the M50/M52/S50 boys!

[Brianmoooore]

The ECU will get very upset, with one ofits primary sensors missing.
Take the cat out if you like, but you still need to fit the lambda.
M18 X 1.5 nut.

[stevetigger]

The problem being is, I havent got the Plug for the Lambda.

Ive seen where it plugs in under the inlet manifold but the exhaust I got with the engine has the Lambda in it but was cut. So no plug end!

Does that make sense?

[DanThe]

the exhaust I got with the engine has the Lambda in it but was cut. So no plug end!

Lazy bastards!
I suppose you could extend the wires and just hardwire it. Leave enough wire on the connector to reattatch though, just incase

[stevetigger]

I get what your saying, but does that mean I will need the lambda put into an exhaust?

I want to use the E30 325i exhaust!

[DanThe]

theres holes for it on your manifolds Steve

Havnt fitted mine yet, thought id try it without first, seems to run ok at the moment

[stevetigger]

theres holes for it on your manifolds Steve

Havnt fitted mine yet, thought id try it without first, seems to run ok at the moment

Thats my plan, but Brian isn't normally wrong!

But yer, holes in manifold.....I forgot.

Im going for start up tomorrow!

[DanThe]

Anybody run one without the sensor?

[Brianmoooore]

You know that ECU fault light you wired up, Steve. You'll find out if it works tomorrow.
I usually get this the wrong way around, but the ECU will interpret the lack of lambda sensor as 0V output from it. I.E. No oxygen in the exhaust = weak mixture.
The ECU will drive the mixture rich, and when it gets no response from the lambda, it will throw the fault light
Since a rich mixture is dangerous to the cat that the ECU expects to be on the exhaust, I expect that it will then alter the fueling and timing to protect it.

[stevetigger]

So on start up will the car go lumpy?


Scrap yard tomorrow me thinks!

[Brianmoooore]

No, because that would threaten the cat, (which I know isn't actually there).
I've never been able to find out exactly what the M50 ECU does when it encounters a problem, but is must revert everything to some cat protecting default values.

[bigkev]

on the renault they run 2 lambda sensors one before and one after the cat,the first one is always changing V's the second runs constant V's so it knows when the cat is knackered.
in my experience when the first one goes it always richens the mixture on the safe side and brings on the ECU fault light so i cant see a problem starting the engine but i would'nt run it for long like that

[stevetigger]

Cheers Kev, Its just a start up tomorrow........then I can iron out this sort of thing afterwards.

[Brianmoooore]

on the renault they run 2 lambda sensors one before and one after the cat,the first one is always changing V's the second runs constant

This is the standard arrangement on modern engines - My M54 has this set up, but there's nothing so sophisticated as this on a M50.
You can start the engine and run it OK. You definitely won't do any damage. It'll just give reduced power and run in "safe" mode.

[Andy325i]

Anybody run one without the sensor?

This is what I have found with my M52B28(no cat fitted):

No O2 sensor fitted: CO level is 0.6%

with O2 sensor fitted and NOT in the exhaust: CO level is 0.1% on warmup and 0.0%!!!!!!!! when warm.

with it plugged in the power loss is very noticable(its hard to spin the wheels in anything but first!)

Andy

[DanThe]

Am I right in thinking the CO level is supposed to be around 0.3%?

Is O2 sensor removal going to be a new performance mod?

[stevetigger]

Am I right in thinking the CO level is supposed to be around 0.3%?

Is O2 sensor removal going to be a new performance mod?

Looks that way!

[Jon_Bmw]

Am I right in thinking the CO level is supposed to be around 0.3%?

Is O2 sensor removal going to be a new performance mod?

CO is supposed to be under 0.3% on a car produced after oct 92, i.e with a cat and lamba.

Pre that it can be up to 3%, so 10 times greater Not that, that is always a good thing mind

[DanThe]

Sorry, I meant ideal CO level for the engine

[bigkev]

jon that reading is taken with a constant throttle at between 2500-3000rpm giving the cat time to stabilize when i test a car the CO is always high and only comes down after about 10-15 seconds this is why you get 30seconds to stabilize the cat while testing
if you give it a few full throttle bursts the CO goes through the roof

[Jon_Bmw]

jon that reading is taken with a constant throttle at between 2500-3000rpm giving the cat time to stabilize when i test a car the CO is always high and only comes down after about 10-15 seconds this is why you get 30seconds to stabilize the cat while testing
if you give it a few full throttle bursts the CO goes through the roof

Yes of course, i'm an idiot. The old CO test is done at idle for pre 92 cars. i was playing about with a CO tester on a 200sx recently and that did a similar thing the CO went sky high when reved, then it stabalizes afterwards.

I'm not sure how true this is of non turbo cars, but it should be to some extent, but if you want to get a car that has a high CO reading through an MOT(like 3%+ CO) cause a vaccum leak in the inlet manifold. Unmetered air can get in and thus make it run lean. Its a very easy trick apart from it sounds like you have a hoover under your bonnet, obviously re connct said vaccum hose/leak before your drive home