0171 and 0174 EML Keeps coming on.

[HuwM]

So I’ve got the P0171 and P0174 codes coming up on my 2.2 54 plate and obviously the EML is on.
It recently had all 4 02 sensors replaced, and I had a new hose from the MAF to the DISA unit ,which is in good order, so now I’m stuck where to look next.
If I clear the code it come back after 1 or 2 drives, and I have a rough idle.
Any ideas would be greatly appreciated.

 

[Number5]

Welcome to the Forum

Check the large wide rubber tube between the air filter and the manifold. It probably has a small split in it and they cost about £30 and it takes 1/2 an hour to replace. Common issue and a simple fix.

 

[HuwM]

Many thanks for the welcome and quick reply, this is great forum group.
I have also replaced this tube at the same time as the MAF to DISA unit just to be safe but I’m still getting the codes come up. Is there anywhere else that an air leak could be coming from.

 

[ph001]

It very commonly the air intake bypass, smaller concertina like hose which tees onto the main manifold. It is quite difficult to spot as the split is usually on the narrower diameter section of the hose.

If it’s not that and you are absolutely CERTAIN you have checked all the inlet hoses, it will be a faulty air flow meter.

 

[HuwM]

Hi, thanks again for the quick response, I had a new main manifold hose fitted about a year ago and took it off again yesterday to double check it and the DISA unit, both of which looked good to me, so I think I’ll have a go at the MAF.
Do you know of any good aftermarket MAFs as I think the original Siemens units are around £350.

 

[ph001]

I would avoid the aftermarket mafs, I think you will end up paying twice. You should be able to return an oem one to bmw if it’s not the issue but I’ve never known P0171 code to be anything else other than split hose or MAF.

 

[HuwM]

Thanks, I thought I would have a go at cleaning the MAF first before I splashed out on a new sensor, so far it looks like a £6 can of Wynn’s EGR cleaner has done the job, fingered crossed.

 

[ph001]

Great outcome if it lasts. People have had mixed results cleaning them.

 

[HuwM]

You were right, I finally bit the bullet and bought a new VDO maf , the Z is now a completely different car, can’t tell you how amazed I am at the transformation. Thanks for your advice.
I found AUTODOC in Germany has the original sensor at half the price on anyone in the uk at £168, and worth every penny.

 

[ph001]

. Great tip on the Autodoc one as well if anybody else needs one.

 

[wonkydonkey]

Another happy Z4 owner Well done, guys!