MAF help please

[Dave_T5]

Hi

After some head scratching and some very helpful guidance from Martin (M-R-P), the decision has been made to try a new / known good MAF sensor.

Can anyone offer any help with deciphering part numbers... I want a Bosch part (the current one is a 2 year old ebay special) and the part number off the old (assumed original) part is 0280218045 / 9470640.

I've found various used examples on ebay but am struggling to find any new parts, depending on which supplier i look at using my vehicle data, it could be any one of the following: 0280218107, 0280218108, 0280218088 and possibly more.

Does anybody know if it matters which i use, and if not, then can anyone recommend a supplier that can be trusted to list the correct part.

My car is a very early phase 2 V70 T5 so right on the changeover.

Cheers

[htomi]

Try Skandix:

http://www.skandix.de

[M-R-P]

Partsforvolvosonline.com are worth a try, Jamie is always very helpful.

[Dave_T5]

Thanks guys

As it happens, the local scrappy had a c70 turbo in with a maf sensor with the same part number- result! (Also checked the one way valves but both already failed)

Got home and fitted it, followed by a reset (battery off for half hour or so), started up and ran lovely, idle settled down to around 700rpm, took for a drive all seemed well until the idle started hunting around 600rpm again, can also tell its running rich by the smell and black smoke. So looks like next step is to replace the front lambda sensor (had fault 280A, faulty signal as well), though this could have been to do with the MAF. Will also try and get hold of a pair of 1-way valves.

[M-R-P]

We can try my maf if you like.

[Dave_T5]

Cheers for the offer, though having doubts it's entirely MAF related...

Removed all coils/plugs, found the plugs all covered in black soot (confirming poor mixture), but all the same so ruled out cylinder specific faults (coil/plug/injector etc).

Now this is what i found puzzling, and quite possibly a red herring, with the covers off i noticed the paint marks on the camshaft pulleys from what i assume were the last cambelt change. Out of curiosity i turned the engine over to see if they lined up and found they were out by at least 1 tooth (possibly 2 depending on which angle you look at it). Also have 644a camshaft control fault, so i reckon the next step is to make sure the timing is 100% correct before delving too far into other components? I am aware the paint marks could be completely irrelevant but the symptons could be attributed to incorrect timing.

[LeeT5]

Would be good if you could post your Fault codes and a good desciption of the symptoms you getting including any visual symptoms.

[Tim Williams]

If you start with the cam timing and then a compression test. Don't forget to check the cam timing you will need a cam locking tool and a new blanking plate for other end of the inlet cam. You can check the cam pulley timing on the belt end but as both pulleys are adjustable it's about as much use as balancing a wheel before fitting a tire.

You can check and adjust the cam timing a small amount without removing the belt.

[M-R-P]

From what I saw, I can't see it being timing...

The rough idle is very intermittent and when first started, it ran perfectly, settling to normal idle as it should. After a while the idle was quite erratic (like marelli etm failure). Weather the vvt fault could be causing this, I don't know.
There was a front lambda faulty signal code which I've seen on mine when my maf was playing up but this doesn't discount an actual lambda fault.

[Dave_T5]

Thanks all, I agree, unlikely to be timing based on the symptoms, have also read up a little bit on setting up the timing with the 'floating' pulleys, so the painted marks could just be academic.

So, current symptoms are black smoke (rich mixture) and very poor idle, almost stalling (worse when warm).

Fault codes at present are:
P0171 - system too lean
P1171 - Fuel adaption (long term trim) too lean
P1633 - Vehicle speed signal

I'm thinking if i have a signal from the lambda sensor saying too lean, the engine will add more fuel hence the rich mixture, but the lambda sensor isn't seeing the change, therefore faulty lambda sensor. Found this in relation to my symptoms as well http://www.volvoforums.org.uk/showthread.php?t=235660&highlight=p1171 Same symptons / fault codes, cured by lambda sensor.

I have checked the connector for the front lambda sensor and all looks ok, but can't see the actual sensor from up top, is it a job from below?

[LeeT5]

Mate, I think your being led up the garden path and putting two and two together and getting 12!

If the plugs are black with Soot then clearly the car is over fuelling. This could simply be caused by a faulty coolant temp sensor, worn (leaking) fuel injectors or even a faulty Crankshaft sensor.
Equally, the ECM could simply be opening the fuel injectors for too long because it's being fed duff info from one of your O2 sensors.
System too lean contradicts the sooting up of the plugs because that's telling you it's running lean, not rich! This is normally caused by an air leak in the manifold, vacuum pipes, internal one way valves leaking, boost pipes leaking, turbo failure, cracked intercooler etc etc.

If you stand any chance of getting to the bottom of this then you need to start thinking methodically and carefully.
Carry out simple checks and monitoring live data.

With the best will in the world your not gonna fix this on your driveway nor by throwing money at it getting a new MAF.

If you monitor live readings then you'll be able to see Coolant temp sensor readings, O2 sensor readings etc. If you don't have any output from one of your O2 sensors, then that's the first place I'd look. Check the wiring and make sure it's not rubbed anywhere and shorting to earth or +.
Again, live readings will tell you that, without getting your hands dirty.

[Dave_T5]

Thanks for the suggestions. The code reader I had at home the other day at can't do the live readings, hence why only going off the codes.

Anyway, I've now tried a different (known good) front lambda sensor, courtesy of m-r-p, and so far all seems good. I have cleared the faults and will see how it goes, but looks like it was the ecu acting off an incorrect lambda signal as you suggested LeeT5.

Now just need to replace the one way valves then move on to the next problem on the list...

Thanks to everyone for the help.