2004 BMW Z4

Noah24 said:
Can’t find anything on service history if sensors have been changed.. would it be money well spent replacing the lambda sensors?
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Personally, I think so, but that all depends on what they cost. If it's not the sensor, take it off and sell it as I would imagine you'll get most of your money back.

Also, I'd buy some of this "Clean Drive Car Van Petrol Diesel" - it's on Amazon and the like, it's what the trade use to flush/clean an engine. It does work, I've used it plenty of times for a whole manner of different problems, so don't consider it to be "snake oil".

But, my first port of call would be to find out what process was done each time to get it working/the light off again, that'll give some indication of where the issue lies. If, for example, they've put in Clean Drive, then you know the issue will be fuel/emissions related, which heads back to the lambda.
 
Basically changed ccv and associated pipes, new bmw disa valve, new rocker cover, new engine oil filter housing gasket. New pipe from maf sensor to throttle body and the small pipe attached. Changed three blanking caps at rear of engine that perish. This work has been done in stages to identify the running lean codes regarding banks one and two as most mechanics thought it would be an air leak. I can confirm there are no air leaks. Mechanic drowned the engine in brake cleaner and the engine did not rev up as expected if an air leak.Then garage clears the code. It takes every time the code is cleared around 150 to 100 miles for the engine light to come back and mostly motorway miles of trips 90 miles plus. Usually at speed not in standing traffic. Light when it pops back up is when car has alwalys been at correct temperature. Today on diagnostic he said emission problems bank one and two running lean. The chap put some stuff in my fuel in a white tin some form of cleaner. The mechanic was revving engine and look at sensor output and they were around 0.4 - 0.7 he sad should be around 1.7 . If that makes sense. Mechanic the cleared codes and engine light remains off. I know that this light will come back on after a 100 spin back up motorway. Therefore do you think it will be the sensors failing?
 
Noah24 said:
The mechanic was revving engine and look at sensor output and they were around 0.4 - 0.7 he sad should be around 1.7 . If that makes sense. Mechanic the cleared codes and engine light remains off. I know that this light will come back on after a 100 spin back up motorway. Therefore do you think it will be the sensors failing?
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Fuel pump, injectors; I guess they're using something like Delphi, both of those cycles can be checked on live data. I'd be starting there..... too lean, the lambda will detect the pre/post burn and give an error. I'd like to know that the lambda sensor is of genuine quality, and that it has been properly fitted.
 
I was thinking the lean banks one and two could be a failing maf, 02 sensors or bad fuel filter. As all vacuum leaks have now been negated.
 
skelters said:
What fuel are you putting in the car?

Running it down to it's empty?
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In all honesty, I have had terrible experiences with Tesco fuel in my Merc. Also my TT. For cars like Zeds, TT's and any performance cars I strongly advocate using high octane fuel. I only use Shell VPower. My tuppence......
P.s more then makes up for the extra few pence spent.
 
To be fair I haven't had any issues with Tesco fuel, but I only put their 99RON Momentum in my cars.

When I had a post-cat 02 sensor issue that gave me an Amber EML on my 3 litre E86 my Indy gave it a dose of Cataclean and told me to only run it on Super-Plus fuel. EML has stayed off for 3 so that seems to have worked.

OP, I hope you can get your car sorted. :thumbsup:
 
Did the guys reading the codes not give you a printout of which P codes it's throwing out? Without knowing those codes it's really difficult for anyone to say what the issues are here.
 
I would get it plugged in and have a look at the live data for the fuel trims to see if they are adding fuel which would be a sign of an air leak, you say thre are no airleaks, a smoke test will reveal any if there are any leaks, best done when the engine is hot so any cracks in plastic parts are expanded at the time of the test. If it isn't air leaks then turn your attention to the Maf, you could also look at what it is doing in live data. Reading should increase with throttle movement. You could try cleaning it with Maf cleaner but in my experience cleaning is hit and miss, had to replace mine and use an oem part not cheap ebay ones, you will end up paying twice, been thre done that etc. Misreading Maf sensor will have an effect on the fueling of the car as the ecu will monitor what is going into the engine and what is passing by the exhaust sensors and alter the fueling to cope with what it is seeing. Over reading Maf may well be causing the ecu to think its running lean and increasing the fuel trims to compensate.
Maf's are not cheap and neither are exhaust sensors so good diagnostics to pinpoint whats gone wrong may well save you cash in the long run.
 
Tesco 99, BP Ultimate or Shell V-Power is all that goes in it.

Wondering if this is a fuel issue causing the fault.
 
Going to get some maf sensor cleaner today. I take it you just spray the sensor that is hanging down between the mesh and plast grids plates?
 
Yes thats the way to do it, ensure its left to air dry afterwards before putting it back in and do not touch the wire or metal part of the sensor with anything or it will be toast for sure.
If that failsto put things right probably best way forward would be to find a member close to you with same engine and try their known good Maf on yours to see if that makes a difference. Better to do that than spend out on a new one, they arn't cheap.
Might be an idea to put in your loaction on your profile and details of your model.
 
Okay used some wymms I think it’s called egr and maf cleaner. Directions for use was just spray it direct into air intake whilst engine running and keep a steady 2000 rpm until can is used up. Done it and no engine light has popped back up. Will see if comes back on in the morning on a 100 mile motorway run.
 
Holy moly took z 4 spin after maf cleaned did the five second dsc button see what all the fuss is about. Wow now that’s a proper fun car brought a smile to my face. Really predictable back end drifts so much fun and a doddle to correct lovely a real passion to drive in that mode
 
Well after maf sensor cleaned and a 100 mile trip this morning engine light remains off so fingers crossed. However run flat red light came on dash but no signs of puncture or flat tyre. How can this light be reset? After I check all tyre pressures?
 
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