Non E30 related question

[mincedbeef]

As well as my E30 cab i've got a 97 E39 528i i use as my daily work horse and took it for an mot today and it failed on emissions
Thinking it could be 02 sensor or cat.
Need to find out the cause so i dont end up throwing cash at it but as i dont have the diag gear, going to take it to a mates garage tomorrow to check it out.
My printout,
Fast idle test
2500-300rpm
CO - 0.30% 0.04%
HC - 200PPM 81PPM

Natural idle test
Engine speed 450 1500rpm
CO 0.50% - 2.86% FAIL

Bugger!
See myself as a good mechanic but when it comes to this sensor b*llocks dont have much of a clue!
If anyone can give me a heads up as what to expect that will be very handy

[bss325i]

So its failed on the CO being to high (2.86%) at idel.

What was the Lambda reading?

[mincedbeef]

Its not listed as lambda.
is it below HC?

[bss325i]

Lambda, CO and HC are three different things.

Lambda is air fuel ratio (about 14.7)

CO is Carbon monoxide

HC is Hydro carbons (un burnt fuel)

If you CO is to high then it could be a sensor fault or the cat.

[mincedbeef]

Cheers for that.
With any luck its not the CAT

[cragles]

Check the air hoses and vacuum hoses for leaks, on my e46 323 (similar engione) one under the top engine cover was split and causing all the emissions to fail at MOT time. Found the split using some brake cleaner (engine revs when brake cleaner sprayed onto the split). Part was about £12

[bss325i]

Check the air hoses and vacuum hoses for leaks, on my e46 323 (similar engione) one under the top engine cover was split and causing all the emissions to fail at MOT time. Found the split using some brake cleaner (engine revs when brake cleaner sprayed onto the split). Part was about £12

This is why i asked the op what the lambda reading was as this can be a giveaway for air leaks.

As you say, common on M52's but also M54's to.