My 1994 440 1.8si idles quite unevenly, and has quite poor fuel economy. From reading around I believe I should be checking/replacing the oxygen sensor.

But... where is it? The haynes manual I have isn't really much help, as I don't really know what I'm looking for, or exactly where it is!!

So, where is it and what does it look like?

Can I test it, or should I just replace it?

Thanks

on the front end of the Cat on the exhaust, its above the cat pointing towards the car.
Grendel

Found it, tested it, and it is dead.

Tried to remove it, but it won't budge! Any tips on getting the thing out?

Its ususually rusted in tight, try warming up the exhaust, it should get to around 600 degrees, but maybe you wont want to work on it when its that hot, but a warmish exhaust (and good heatproof gloves) should see it loosen, its quite a coiarse thread so once it goes it will be easy.
Grendel

I am having a similar problem with 440le 1.6petrol. In idle i get abit of vibration shaking the dash (abit) and it seems to search for idle revs. This car has been off the road for 2 months it is in good condition otherwise, MOT was last week and the garage didnt notice it when checking but it seems to happen occasionly but can be quite anoying when in traffic.

Could still be, what were the emission results, mine are usually way low, but even without the oxygen sensor they can be within the limits for the MOT, my CO2 is usually around 0.04% and hydrocarbons about 40ppm, allowable to get through the MOT are up to 3% CO and 1200ppm hydrocarbons.
Grendel