EMU emission sensors

For the M Powered Z4 derivatives
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Joined: Fri 27 Apr, 2012 01:25
Posts: 215

  Z3 roadster 3.0i

EMU emission sensors

Post by Z3andZ4 »

Hi all

Z4M coupe Sept ‘06 done 44,000 miles.

After being SORN through lockdown etc returned to the road and immediately got the orange EMU light.

Local workshop advising all FOUR, yes FOUR, emission sensors need changing out at £240 plus VAT each plus labour.

Any idea if all four sensors are the same - been told 2 pre cat and two post cat. But even so surely the chances of all four being shot at the same time are close to zero……..

Any help or advice seriously appreciated.

Meanwhile in other news my Z3 will clock 130,000 next month!!!!!! Still love her too.

Thank you anyone replying.

2001 Z3 3 litre Sport Roadster - titanium and special
2006 Z4M coupe - Interlagos and red
http://i1167.photobucket.com/albums/q62 ... huiwqu.jpg
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Joined: Sat 05 May, 2012 22:46
Posts: 690

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: EMU emission sensors

Post by colb »

Extreamly unlikely for all four to fail, I would want to put diagnostics on it to see what codes it has set then take a look at live data from the individual sensors to see what they are doing. Pre Cat should be showing up in graph form as a regular wave form as their voltage ranges up and down, if they show up as static then that would be an indication of a fault with them as would be no signal showing up. Post cat sensors usually appear pretty static until they detect fuel content in the exhaust gas then react accordingly.
Its worth checking for air leaks in the vaccum system across the engine from Post Maf to exhaust these engines require a good sealed vaccum system to run correctley, check all rubber and plastic vaccum hoses for splits or holes. Air leaks that enter after the Maf are not measured by the Maf and will be picked up in the exhaust sensors fooling the car into seeing a weak mixture which in turn commands the EMU to increase fuel at the injectors to richen the mixture up. This cycle will go on until its adding up to 20% more fuel then gives up and lights the EML on the dash to draw attention to it. Live data will show fuel trims at an elevated level which is another pointer to air leaks being present. A smoke test is probably the easiest way to find air leaks if visual checks fail to find any.
Since the cars been laid up for an extended period I wouldn't be surprised if somethings failed and causing an air leak.
Where are you based, if near me I would take a look for you.
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
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