Another thing after another

UK forum for general and technical discussion about the Z3 roadster

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Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 76

  Z3 roadster 1.9

Another thing after another

Post by Parki » Thu 30 Aug, 2018 12:34

Hi - I noticed my mpg was getting worse on my 1.9 '97 automatic & invested in a code reader which indicated -
'OD Oxygen sensor heater before catalytic converter &
OA Oxygen Sensor upstream of catalytic converter'. I cleared the codes but they came back.
I have only got 1 sensor which is before the cat & have had it replaced during a previous low mpg problem.
The cat section was 'blowing' & in poor condition so this has been replaced.
I have cleared the codes again & just returned from a 30 mile round trip. mpg seemed marginally better but checking the code reader, I now see -
The OD & OA sensors as above PLUS '1A Multiplicative mixture adaption (part load) control limit reached'
If anyone can explain what this means I would be very grateful. I can smell like burnt paint & wonder if the cat needs to 'settle down'?

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3363

  M roadster S50

Re: Another thing after another

Post by pingu » Thu 30 Aug, 2018 13:32

You may have a leaking air pipe after the MAF.

e.g. The MAF is sensing 50 litres/minute, but the engine is getting 60 litres/minute and the ECU is getting confused as it can't up the fuel injection time to compensate for the excess air sensed by the O2 sensor.
Pingu

Bumpa
Joined: Fri 23 Jun, 2017 21:31
Posts: 47

  Z3 roadster 2.2i

Re: Another thing after another

Post by Bumpa » Thu 30 Aug, 2018 19:23

Pingu may have a point. On my 2.2 I got "Fuel Trim" errors which turned out to be splits in the air trunking between the MAF sensor and the throttle body. The two bits of trunking were less than £30 and once fitted all was well.

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 640

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Another thing after another

Post by colb » Thu 30 Aug, 2018 21:18

Agree, check all rubber connections and pipes from Maf forwards for any cracks or splits, seems the exhaust sensor is seeing more air and demanding a richer mixture hence the increase you see in mpg. Its reached a point where the ecu cant keep up with what its being told and can't change the settings anymore. Find the leak and fix it, clear codes and run it then re check for codes. If you have software clear the adaptions and let the car reset its self over time once you have no leaks and no codes being set.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 76

  Z3 roadster 1.9

Re: Another thing after another

Post by Parki » Fri 31 Aug, 2018 08:22

Hi - thanks for the replies - I have tried checking hoses etc before & couldn't see/feel any problems but I will check again.
If I don't find anything, any ideas where should I be looking next?

therealdb1
Joined: Tue 25 Jun, 2013 22:47
Posts: 263

  Z3 roadster 2.0

Re: Another thing after another

Post by therealdb1 » Fri 31 Aug, 2018 23:13

When checking the rubber hoses you really need to take them all off the car, squeeze and bend them including the small ones that T off the belows unless there is a really obvious tear. You cannot inspect them properly in situ by simply popping the bonnet.

Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 76

  Z3 roadster 1.9

Re: Another thing after another

Post by Parki » Sat 08 Sep, 2018 09:06

Update - after looking/feeling around the hoses but reluctant to remove bits to gain access (I invariably break something or lose bits so it ends up costing more) I took my z out for a spin again & mpg seemed to pick up & on return the 3rd code fault had disappeared leaving the O2 sensor fault. I took it to Autobahn in Hexham (German car specialist) who said existing sensor was a cheapo & recommended to fit a Bosch. cost £100 but travelling home got figure of 40.4 mpg which seems to suggest its sorted(?) Once again thanks for all help & guess it shows its worth paying a bit more for bits sometimes.

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 640

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Another thing after another

Post by colb » Sat 08 Sep, 2018 10:00

Seems you got it sorted and learnt a lesson oem parts every time from now on.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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