Can any of you good people help me ?

[walrus5668]

wonder if anyone can help ... i got a m52b28 in my z3 .. ive done various mods m50 manifold , bbtb, full ss performance exhaust, decat, remap .. recently ive had probs with the car i had to change the cam and crank sensor but the car ran fine with all the mods mentioned before those sensor problems... now i have a situation where its using more fuel than usual and although it runs well and pulls as it should im getting loud popping on overun ..also on tickover it sort of misses slightly, very slightly but something just isnt right .. ive changed the plugs .. no better .. any ideas

[BladeRunner919]

Have you checked for fault codes in the ECU? Also, where did you get the cam and crank sensors? If they're not genuine BMW parts, they could well be the cause of problems.

[Gazza]

Unplug the MAF and see if that makes a difference

[walrus5668]

yeah no codes been thrown up ... yeah i might have to go bmw parts as i had read that there was a problem with non bmw parts .. only after ide changed them

[walrus5668]

ill try that Gazza .. thank you guys ..

[walrus5668]

ok so the car was at idle and up to temp.... it was doing the normal tiny hiccup thing on idle .. i unplugged the maf and it never changed anything ... i then plugged the maf back in while it was running and it sort of lowered the revs for a second then went back to the same as it was before .. hicupping now and then ... any advice would be appreciated

[BladeRunner919]

What are you using to check for codes?

[walrus5668]

it was a proper bmw computer that a freind has as he works at bmw ... hes very busy so i cant even ask him advice as hes away atm

[BladeRunner919]

But he's run a check since you swapped the parts and since the problem started and it's come back clear?

[walrus5668]

it showed crank and cam sensor faults .. but the car was running with the same problem as i have now but it would cut out when warm then not restart until cooled .. he said classic crank sensor .. i changed them the car stopped cutting out when warm ..but was there the problem is as it is now , hiccuping and popping badly on overun .. i thought it might just need a run out . i gave it a quick run out and the present problem remains .. i got another freind with a snapon comp to check .. no codes ..

[BladeRunner919]

A Snap-on diagnostic will only (I believe) show generic OBD faults - you need a proper BMW scan to get to all the codes. I still vote for the aftermarket sensors as the most likely problem.

[Del]

It can suggest a manifold leak on a normal engine. On a high performance engine a certain amount of popping on overrun is normal and acceptable. I believe there is a strong clue in this happening immediately after a sensor change. Loud popping is caused by slightly too much fuel continuing to come into the combustion chamber despite easing off the accelerator; it will exit via the exhaust valve and explode in the manifold/exhaust. As it coincided with a sensor change this hints to me that the inlet/exhaust valve “timing” might now be slightly off.

As said already, and on other “BMW track” forums I have seen, I would only use top quality BMW cam sensors.

[Mr Silver]

It may be that the problem lies with your initial fault, cam sensors. It is well documented that many 'alternative' sources of cam sensors originate in China and are as reliable as a chocolate kettle. It may be wise to refit the originals and then carry out another diagnostic, in other words, start over fresh. You should be able to detect the change in the sensors which may help to narrow down the problem. I wish you luck.


Regards.

[walrus5668]

ok solved problem ... was the shitty non bmw cam sensor ... i got hold of a bmw one and just changed it .. problem solved .. thanks for your help