940 turbo lambda

[Mattty]

Another day - another problem. Feel like I'm posting on here every other day so apologies for that. Car is a 1997 945 2.3 turbo.

Well about last week I was driving down the road and my lambda/engine management light came on. Drove for another couple of minutes because I was in traffic and couldn' t stop. Pulled over and found that all the wires on my lambda sensor - located on the underside of the downpipe just after the turbo - has completely detached from the sensor. However, the car seemed to be running fine and without issue, so for the last week I have been driving with the lambda light on, but the car has been running ok.

So came out of work today - no lambda light on the dash. The bulb still works and lights up initially then goes out when the engine starts. Checked under my bonnet to make sure I wasn't going insane and to my relief, strangely, the wires are definitely still not attached to the sensor.

So my questions are; 1) How was/is the car running ok without the sensor? I thought faulty lambdas usually cause cars to run like a bag of ****e? And 2) Why is the light no longer illuminating?

Thanks for any help 😊

[Laird Scooby]

Firstly, all engine management maps have a set of default values built in - "Limp Mode" - whereby the engine will run reasonably until the fault is diagnosed and fixed.

However, that default map is only approximate, all things to all engines so some will run better than others on it.

You need to get a new Lambda sensor in there ASAP and once fitted, remove fuse #1 for a couple of minutes to erase the fault codes from the ECU. There's a +12v feed to one part of the Lambda sensor for the heater inside it, if that wire shorts to earth it could cause a lot of problems! It comes from the same feed as the injectors get their power from so could potentially leave you stranded.

As for why the EML has gone out - that's very tricky to guess at without seeing the car and performing several tests and a detailed inspection. I could make a guess that the sense wire on the Lambda wiring has shorted to the earth wire in the harness that feeds the Lambda sensor so the ECU is seeing a weak mixture and thinks it's running ok or possibly even the sense wire has shorted back onto the connection within the sensor it should be on.

Whichever way you view it, new sensor ASAP and go from there!

[TonyS9]

The lack of a warning light is mystifying. But cars ran perfectly well before these sensors, and in reality they don't do an aweful lot. As far as I can tell (and I have some fuel instrumentation) they are mostly used in idle to run a lean idle. The rest of the map is adjusted just a little by these results and it just eliminates the need for manual adjustment. At the end of the day day the car runs pretty rich because the load is not measurable quickly enough. Idle is a known load mode, so has signals to tell the ECU things like AC and auto drive engage.

The car 'should' run fine without it, but as said there maybe a variance between cars.

[Mattty]

Thanks for the info guys. Looking at lambda sensors, theres a pretty huge disparity in price. I get that tye cheaper ones wont be as long lasting as the more expensive options, but should this sensor from ebay be ok?

https://rover.ebay.com/rover/0/0/0?m...2F161575793902

[Laird Scooby]

As long as your engine code is in the listing you should be ok - i've had sensors from the same people without a problem.

Let us know how you get on!

[Stephen Edwin]

Originally Posted by Mattty

Another day - another problem. Feel like I'm posting on here every other day so apologies for that. Car is a 1997 945 2.3 turbo.

Well about last week I was driving down the road and my lambda/engine management light came on. Drove for another couple of minutes because I was in traffic and couldn' t stop. Pulled over and found that all the wires on my lambda sensor - located on the underside of the downpipe just after the turbo - has completely detached from the sensor. However, the car seemed to be running fine and without issue, so for the last week I have been driving with the lambda light on, but the car has been running ok.

So came out of work today - no lambda light on the dash. The bulb still works and lights up initially then goes out when the engine starts. Checked under my bonnet to make sure I wasn't going insane and to my relief, strangely, the wires are definitely still not attached to the sensor.

So my questions are; 1) How was/is the car running ok without the sensor? I thought faulty lambdas usually cause cars to run like a bag of ****e? And 2) Why is the light no longer illuminating?

Thanks for any help 😊

Before replacing the sensor, possibly putting a new sensor at risk, can you see any cause why the wires are detached?

Are the wires known for "spontaneous detachment"?

[Mattty]

Originally Posted by Stephen Edwin

Before replacing the sensor, possibly putting a new sensor at risk, can you see any cause why the wires are detached?

Are the wires known for "spontaneous detachment"?

When I last had the downpipe off they were already looking a bit worse for wear but I ended up leaving it and forgetting about it, to be honest. The car has done 250k miles and looking at the service receipts from the last 20 year owner, seems like its the original one in there