Year of Manufacture *: 1998 Engine Size and Code *: 1895cc 19-4S-1 ( Optional ) ECU Type: Motronic M5.2 ( Optional ) Scanner Used: Snap on Solus
Hi people looking for a bit of guidance on this one please.
This Z3 has failed its MOT on high emissions being to high. Forgot to bring the fail sheet home so cant remember the reading but on our machine they were all over the place CO 0.4/2.5 Hc 50/400.
Bit of history of the vehicle, it has been parked up for about 3/4 years now because the owner had a child, but last week we were asked to fetch it and carry out a service and mot so they can use it again. Service went ok we did all the usual oil filter, air filter, fuel filter, plugs and an oil flush then off for mot to have it fail only on emissions. Spoke to the customer and they have informed me there has been a bit of history with emissions with this vehicle in the past. They told me that it had a cat in 06 for mot and new MAF sensor in 07 all to get it through emissions. Every time it still didn't go through without the mot station revving it flat out for ages according to the customer. I know its been a few years now since cat and MAF sensor were fitted but up to now its only done 60k miles and was only used in the summer till it was taken off the road in 2009 so I cant see these being the fault (but I know it could still be). I have spoke to the customer and said that I could stick a cat on it and it would probably pass but next year we would be in the same boat again, so its time to fix the fault and not the affects of the fault.
This is what I have checked so far .....
The only Fault codes were for Cam sensor and O2 sensor. Scoped the cam sensor and found no trace so fitted a new cam sensor and now ok, but the O2 sensor I think was me but when talking to the customer he was convinced this was the fault because he had read it on the internet and told me to try it, so I fitted a new Bosch one (the old one didn't look that old and that was also a bosch one).
Fuel pressure is at 40psi running with the vaccuum disconnected and 35psi with it connected. The injectors are switching at 2.8ms.
Smoked the inlet to only find 1 tiny tiny leak from the DISA valve. That's now fixed. I have also disconnected and blanked the rocker to inlet pipe which made no difference.
Compression test all about 180psi (AD says 145/160) Is that too high???? Also I have done a cylinder leakage test all ok and about the same.
MAF sensor 0.8v on tick over and 4.2v WOT. So that should be ok
ECT 70c-1v 80c-0.9v. No drop outs. AD does say 80c should be 0.8v.
Powers and grounds to the ecu all ok KOEO and KOER.
O2 sensor - this is where I'm stuck when I scope the sensor it switches between 1.7v and 0.8v and the earth is at 0.75v. Is this a "floating earth" or a bad earth. Because on live data it reads 0.1v and 0.8v. If I earth the sensor out the emissions go off the scale and I get a code for O2 sensor ground to earth so I'm thinking the 0.75v is right and its a floating earth but I dont know.
Many thanks and I hope this reads ok and makes sense.
Andrew
Re: BMW Z3 High emissions
Posted by aidan birley on May 11, 2013, 6:08 pm, in reply to "BMW Z3 High emissions" Aidan Birley
Hi
You will need to post all 4 gas readings + lambda at idle & cruse to get meaningful advice.
The lambda readings are vital for diagnosis.
If it was an after market cat fitted 5 years ago it will almost certainly be useless !!!
I would guess you are correct about floating earth, what happens when you use a single channel and connect both scope wires directly to the sensor
I'll try and nip back to work and get the fail sheet and I'll do another one on Monday, but they are all over the place dont think they I have had the same reading twice. But you are right vital for diagnosis.
To be honest I haven't used the sensor earth and signal at the same time. If I use the sensor earth and it starts switching the same as live data it will prove it's a floating earth. The floating earth idea only came to me on the way home today and I've not had any time to prove it.
It looks an after market cat by the size of it, its probably half the size of the original one I'm guessing.
Sorry I forgot to say before I havn't checked LTFT and STFT this would help prove the vehicle is in control of fuel wouldn't it, then and prove it is more a cat issue rather than fuel issue.
Many Thanks Andrew
**** UPDATE ****
Been back to work and got the fail. I know you will want 4 gas readings idle and fast idle but this is what I have now....
IDLE FI 1 FI2 CO - 0.413 0.480 0.396 HC - ~~~ 97 79 LAMDBA - ~~~ 1.005 0.999
Can i just add that the tester held it close on flat out for 5mins before getting this resault. He had the idea that if he got the cat RED HOT it would work
Re: BMW Z3 High emissions
Posted by Andrew Windle on May 13, 2013, 11:54 am, in reply to "BMW Z3 High emissions"
I have done the gas test first thing today. I thought they were more all over the place but looking at them now they may not be.
STFT - -11.4/8.6 but had a average of 3.5% This should prove fuel delivery/quantity is ok?
I scoped the O2 sensor using the sensor earth and it now switches between 0.011v / 0.900v. So does this mean that the 0.75v on the earth is a floating earth?
I'm starting to think that the aftermarket cat is no good!!!
Many thanks Andrew
Re: BMW Z3 High emissions
Posted by Pete Mutlow on May 13, 2013, 8:00 pm, in reply to "Re: BMW Z3 High emissions" Peter Mutlow
Hi Andrew,
"I'm starting to think that the aftermarket cat is no good!!!"
I think you are right!
Regards
Pete M
"
Re: BMW Z3 High emissions
Posted by aidan birley on May 13, 2013, 8:24 pm, in reply to "Re: BMW Z3 High emissions" Aidan Birley
HI Andrew
I'm with Pete, classic c__p after market Cat.
Idle readings could be a little better but I would say just down to age of vehicle.
It's worth remembering that the Lambda reading is calculated value from other gases and (in theory) is the same irrespective of if the cat is working or not.
As a general rule if the lambda reading are good but HC & Co are high it indicates a Cat fault.
The biggest problem with lambda readings are that it relies heavily on o2 reading so any leaks will cause incorrect calculated value. this needs to be remembered when relying on it for diagnosis.
Of course if it is a down stream cat it is simple enough to drill a test port pre cat
Alan Modified emission testing was for the High pressure petrol injection engines running stratified, so lean that lambda would be 1.7+. Ed Kaps
Fixed #
Posted by Andrew Windle on May 15, 2013, 8:18 pm, in reply to "Re: BMW Z3 High emissions" Edited by board administrator May 20, 2013, 2:30 pm
Job done a new cat sorted it.
I dont know what the biggest shock was ...£740+ for the cat or the go ahead on the job from the customer. I really thought it was going to be game over for it.
Many thanks for all the help and very interesting document from Aidan. Wont confess I understood it first time I read it but after I sat and read it a couple of time I think it has gone in. It's one of them bits of information that will be used time and time again from now on.
On another note and I think I might know the answer but are there ANY good aftermarket cat available. I only use genuine ones but even on a vehicle like this the price of the cat+ mot+ lab it was very touch and go if it was worth it.
Thanks for that Ed, An interesting topic & I've learned a bit. I still don't see why a high lambda reading should be anything to do with an Mot test, (my bet is its to stop the tester pulling out the pipe during the test).
Re: BMW Z3 High emissions
Posted by Pete Mutlow on May 16, 2013, 11:57 pm, in reply to "Re: BMW Z3 High emissions" Peter Mutlow
Hi Alan,
I think you are on the right lines. As you know the Lambda reading incorporates 02 and I can remember many occasions (in pre-cat days)I used to create an air leak to get a vehicle through an MOT test. I am not a MOT tester incidentally. With the Lambda reading this is no longer possible with a vehicle that has to meet the more stringent test. However, what galls me is that I have attended vehicles with failed Lambda readings because the owners did not realise they had an air leak. So in effect the vehicle has failed the MOT test not because it is polluting the atmosphere, but creating too much oxygen!
on May 11, 2013, 6:08 pm, in reply to "
