Have I got this right - o2 sensors

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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Have I got this right - o2 sensors

Post by TomH84 »

Hey guys,

I'm planning to swap out the front o2 sensors as part of regular preventative maintenance.

Carpartsforless/Eurocarparts list a range of options for my 2002 2.2i M54 engine. Trying to narrow down the right parts...

It seems like I need two different Bosch sensors - one longer than the other. Sound right?

The cylinder 1-3 sensor is 570mm:

http://www.carparts4less.co.uk/cp4l/c/B ... 0&1&000210

The cylinder 4-6 is 980mm.

http://www.carparts4less.co.uk/cp4l/c/B ... b&1&000210

Cheers!

ps. Will also buy an o2 sensor tool. These sensors look like a right bugger to access!
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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pingu
Joined: Fri 30 Apr, 2004 16:01
Posts: 3412

  M roadster S50

Re: Have I got this right - o2 sensors

Post by pingu »

My recommendation is DO NOT touch them if there is nothing wrong with them.

They will probably be corroded in and you will damage something replacing them.

There is a good possibility that you will just be introducing a fault.
Pingu
bertiejaffa
Joined: Fri 26 Jul, 2013 09:28
Posts: 1733

  M roadster S50
Location: Manchester

Re: Have I got this right - o2 sensors

Post by bertiejaffa »

pingu wrote:My recommendation is DO NOT touch them if there is nothing wrong with them.

They will probably be corroded in and you will damage something replacing them.

There is a good possibility that you will just be introducing a fault.
I'd agree - theres enough to fix on them as it is :lol:
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colb
Joined: Sat 05 May, 2012 22:46
Posts: 690

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Have I got this right - o2 sensors

Post by colb »

I agree with the others, don't mess with them unless they are setting error codes or slow to respond which you would see in live data on diagnostics. They either work or they don't, changing them out will cost you and may be a waste of money.
Usual fault they develop is the heater circuit burning out which would be revealed by setting an error code.

Colb
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Have I got this right - o2 sensors

Post by TomH84 »

ok guys - thanks. I'll check voltages before committing to replace. Looks like a fiddly job.

My reason for replacement is that my long term fuel trims are still high. They are at about 12 (bank1) / 9 (bank 2). That's at the limit before the engine light comes on (it's 12% I think). The CEL is off right now, but will likely come back at some point.

I've done a smoke test and there's no intake / vacuum leaks at all (confirmed by correct short term trims!). Got me thinking that my problem is either (1) o2 sensors; (2) MAF; or (3) lazy fuel pump (filter already replaced). I'll keep investigating. Replacing o2 sensors seemed a cheaper first go than switching the MAF...

Cheers.
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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colb
Joined: Sat 05 May, 2012 22:46
Posts: 690

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Have I got this right - o2 sensors

Post by colb »

If you have access to a live data diagnostics I would check what the Lambda sensors are working, you should see them switching up and down with the engine running to produce a regular signal.
The Maf may well be the cause of your troubles it may be dirty r failing to report correctly without setting a code.

Root cause of my running problems was the Maf, changed that out for a Bosch replacement which put things right.
Do not waste money on pattern parts go for OEM.

Colb
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Have I got this right - o2 sensors

Post by TomH84 »

Thanks. Yes, I've got a code reader with live data. The pre-cat sensors are switching voltage - though one seems to be less response than the other. Given that both banks are reading high, it does suggest a MAF issues. I'd be unlikely if both sensors failed.

Maybe time to bite the bullet and buy a new MAF. Will definitely go Bosch. Heard to many tales about dodgy e-bay MAFs.

Cheers
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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