lambda sensors

[lefty007]

Is that it tug?

[tug]

Thats the regulator buddy. Hope it is that for you mate.

[lefty007]

When I type in fuel regulator it comes up with a thing resembling a float do you know the correct name for this item or send a link to it thanks

[lefty007]

It’s the throttle body

[tug]

Sorry mate, yes the throttle body (duh! my mistake ) this is the one;
https://www.ebay.co.uk/itm/204087764728 ... q1AgYMbcS0

[lefty007]

Would this have something to do with the emissions that my car is failing it’s mot on

[tug]

It could do, but it would more than likely have a lot to do with over fueling which would lead to that. Take it off mate and make sure that the flap is still stiff & not easily "flapping" about. Mine was moving with no effort needed, whereas the new one needed a concerted effort to move it.

[lefty007]

Sorned for the winter but thanks for all your help tug start again next year.

[colb]

Best course of action is to arm yourself with a decent diagnostics tool either handheld or laptop based so you can take a look at live data from the exhaust sensors and the fuel trims to see if they are working correctly and the fuel trims are in spec. When viewed in live data the pre cat sensors should be producing a nice wave fporm in graph view as they range up and down their voltage range. The post cat sensors should be less active and sit as a stable line unless they are picking up excess fuel in the exhaust. Once you know what they are doing take a look at the fuel trims, if there is an air leak somewhere across the engine from Maf to exhaust the pre cat sensors will pick up the unmetered air that has entered and not measured by the Maf sensor will cause the engine computer to believe the car is running lean and demand the injectors to add more fuel to compensate. It will keep adding fuel to try and compensate until it is adding 20% more fuel before deciding something is wrong and then sets the EML on the dash to draw attention to it. High fuel trims is a good indicator that there is an air leak somewhere across the engine. Check all rubber vaccum lines and intake boots for cracks and splits, replace any that are found. Finding air leaks is best carried out by doing a smoke test by pumping smoke into the intake boot after the Maf sensor, best done by taking the Maf off the car and using a rubber glove over the boot and pumping smoke in via a hole in one of the fingers. Hold the throttle open at the pedal so the smoke can flow in freely. Once the smoke is in there take a good look at all hoses and everything else across the engine for escaping smoke. Pay particular attention to the dipstick tube that has a O ring in that can go bad and allow air in. Take a good look at the cam cover for any signs of escaping smoke, plastic cam covers are known to degrade and crack causing air leaks. As suggested earlier check out the exhaust manifold for cracks. Any found will require replacement to achieve a good vaccum seal across the engine. BMW engine are really fussy when it comes to a good sealed vaccum system.

[lefty007]

Had smoke done and came back no leaks replaced upstream and down stream 02 sensors. Had emission test done and came back over fuelling.

[colb]

How is your Maf performing, if its misreporting what air has passed through that could affect your fueling besides duff exhaust sensors if you are certain there are no air leaks.

[Z4Mariner]

Good advice to get a diagnostic tool capable of real time data logging. You'll be able to monitor the MAF measured air flow as well as the O2 sensor voltages. The E46 I used to own gave me the 'opportunity' to do a good bit of data logging to find and fix vacuum leaks as well as install new O2 sensors and eventually a new MAF.

Colb is right on target in noting that a degraded MAF can give low air flow data, which leads to lean air/fuel ratio, which leads to increased fuel trim - and none of this will set the CEL (SEL) until it hits a threshold (usually 25%).