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[b]***UPDATE 1st April 2016***
- Oddly there is no secondary air system on my 1997 Z3.
- I had a tetra clean performed, it made no difference although my MPG increased by 5
- Crankcase breather pipe was a little clogged up so was replaced.
[li]My long term fuel trim was steadily increasing, at one point it reached Minus -16%, so….
I installed a new pre-cat sensor even though reccomended replacement interval is 100,00 miles and mine has 60,000,
This made a huge difference and brought the LTFT down from minus -16% to minus -6%, I know ideally that LTFT’s should be zero.
Also the update intervals on O2 sensor is now reduced from approx 4 seconds down to 2 seconds.
anyway, UK MOT is due next week, so fingers crossed
[/b]In an effort to diagnose a rich running car (fuel smell from exhaust & UK MOT Emission’s Fail), i decided to monitor STFT’s, LTFT’s & O2 data etc.
These readings/graphs were taken from a Titania PRE-Cat o2 Sensor on a UK 1997 2.8L BMW Z3 Roadster, Engine M52B28, Control Module=DME Siemens MS410DS3.
The car is nearly 18 years old with 57k on the clockFrom what i understand the time it takes to switch from lean to rich should be a couple of times per second with Titania sensors but on my graphs it appears to be taking on average every 4 seconds,
but could anyone confirm this?
Or could it be that this 4 second switch is normal for the Siemens MS410DS3 control module?The readings were taken during idle and after a 10 minute drive on the motorway.
There are no OBD codes, car seems to drive and Idle fine with no hesitations.Ive attached 2 x pdf’s showing graphing of the one and only sensor on the vehicle which is a Pre cat O2,
also attached are 2 x pdf’s showing STFT’s.I dont want to start needlessly throwing parts at this car where they are not needed, but before I continue to diagnose what seems to be a rich condition, I’m thinking the O2 sensor should be changed before I check any live data again and/or move onto the injectors, fuel pressure regulator etc.
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[quote=”cap269″ post=137039]What was the reason given for the emissions test fail?[/quote]
I can’t remember exactly which of the two it was… Hydrocarbons i think but don’t quote me
Im concluding its the sports cat not up to temperature but i need to do a fuel pressure test.
technically it failed but only marginally, fortunately he’s a friendly tester who Ive known for a long time so it was passed, i don’t know how because i believe the test results are sent live to VOSA, regardless though I wanted to get to the bottom of the reason/s why and correct it.
Ok. A malfunctioning EGR system can cause high HC emissions because the un-burned fuel in the exhaust isn’t recycled. This can also damage the catalytic converter, as well as cause a slight rich condition at speed (EGR doesn’t operate at idle or wide-open throttle). While you’re checking things out, check the EGR valve. Remove the valve and check that the diaphragm opens and closes when you manually apply vacuum. Remove any carbon around the port on the intake manifold (if it is clogged make sure to clear it all) and EGR valve body. With the EGR valve closed blow into the exhaust tube side and make sure no air passes through. Check the EGR solenoid to make sure it turns on and off (clicks when power and ground is applied). Check to make sure the solenoid doesn’t leak air when it is energized. Check this by plugging the port that goes to the EGR valve and apply hand pump or mouth suction to the manifold vacuum port. If it doesn’t hold vacuum or bleeds vacuum slowly, it should be replaced.
After doing a little research, it turns out the BMW Z3’s don’t have EGR valves, but the info is much appreciated and noted
[quote=”cap269″ post=137090]Yes, they do, but the German makers call it “secondary air system” — same thing.[/quote]
Aha ok,
so just to confirm the parts you mention will be #1 & #5 on this page?:-
http://www.realoem.com/bmw/enUS/showparts?id=CJ32-EUR-01_1997_Z3_BMW_Z3_28&diagId=11_6225#11727540472Part number 11727540472 described as an Air Injection control valve
attached diagram from:-
http://blog.bavauto.com/12072/bmw-secondary-air-system-fault-code-diagnosing-how-to-diy-obd-ii/
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