Lambda Probes and Sensors

Folks,

What is the difference between a Lambda probe and a Lambda sensor? I need to buy the part but I don't know what I need to get? My fuel consumption is still bad and this is the only part of the system that hasn't been changed out. My exhaust outlet has blackened so I am assuming that there is an over-rich fuel mixture due to the original lambda (probe or sensor) still being in the car.

Thanks,

Colm
1992 Volvo 850 GLt 2.0 20V with 141k miles on the clock!

[warthog]

Colm,

'What is the difference between a Lambda probe and a Lambda sensor?' - they're one and the same.

There were two different types of sensor fitted to the 850's. I think that one is only available from Volvo, but the other can be got from GSF, ECP, or your local Bosch agent as well as Nordic etc.

Using non-leaded fuel you wouldn't expect to see the old grey exhaust tailpipe, but have you pulled any fault codes? If the sensors were at fault or the mixture continually rich I would have expected to see codes logged.

Have you a friendly local garage that can do an exhaust gas analysis for you (the same that's done for the MOT)? This would show up mixture or Lambda probe problems and would be a lot cheaper than replacing a probe without a fault.

Regards

[bigandquick]

Better still get a specialist with a scope to check the functioning of your Lambda sensor. I don't hold much faith in MOT testing gear when mine was passed recently with a totally knackered Lambda sensor in situ.
There is much more to the fuelling than just the Lambda probe - have the whole system checked thoroughly by someone who knows what they are doing - it will save you in the long run.

[cootuk]

From what i've read I thought the ecu could easily throw the lambda probe data away and just guesstimate the fuelling from other sensor data and the standard mappings. Certainly when mine was faulty the car still ran fine so i assumed it dropped back to a more lenient fuelling map.

[bigandquick]

You could probably get away with it for a while, but mine was overfuelling as result, fuel consumption was up, performance was down. My way of thinking is that if it's there, it's there for a reason, and certainly the Lambda sensor is.
A functional sensor will react almost instantly to changes in the level of oxygen in the exhaust and let the ecu adjust accordingly and run the engine optimally, rather than best guess. But it is only one piece of the jigsaw, and I emphsise the best course is to get the whole system checked properly.

I will say that when I replaced my sensor I was lucky not to cause a problem with the ecu by not having it re-set at the same time. This does not involve just cutting the power to the ecu for some minutes as has been suggested on other threads/forums. This will definitely not work on original ecus and can cause spurious faults to be stored. I will not elaborate more on this forum, suffice to say entrust it to a specialist, and if a dealer ever says you need a new ecu get a second opinion.

Hi guys,

I go the emmissions checked out this weekend for the princely sum of €10 (about £7). The mechanic said the emissions were great on the car and it would pass the NCT (MOT) without any bother. Having cast an eye over the rest of the car and listening to what work I have done on it to date, he said the injectors probably needed cleaning. I got a bottle of injector cleaner and put it into the tank the results are amazing. The car pulls a lot better and the mpg has improved (but has yet to be measured).

Regards,

Colm