Keep blowing my MAF sensor

[37831999]

Hi all I had my car for 3 weeks now, first week ran fine with no problems, 2nd weeks started miss firing and smoking, changed leads, plugs, rotor arm and cap, turned out to be MAF sensor, put it on and ran fine for a week, then the same problems started happening, got a sensor under warranty and it ran perfect for all of 15minutes! Then blew again! Please help! Also I have no engine management light on? Not even on ignition? Mine is a M reg t5 should it have one?

Any help would be great as at the moment I've disconnected the MAF sensor and am getting 11mpg!

[nobananas]

Can't see how you can blow a MAF sensor. They have a 12v feed but it's off the same circuit as the injectors and many other components (thinking overcharging alternator here but I would think you would see other problems). One option is that the MAF's are aftermarket and not up to scratch (have you tried a genuine one, even a second hand unit ?) another option is that the MAF is getting contaminated somehow, possibly from oil (if the engine is breathing a bit) or maybe from an over excessively oiled cotton/foam air filter. I have also seen a foam filter shedding and dropping pieces into the intake that then stick to the MAF hot wire.

[37831999]

Hi I don't mean blow as such but just becomes faulty quickly? The one I purchased was a Bosch sensor which I believe is what Volvo would issue me anyway?

[Alan M]

A fault code usually appears and shows itself as a management light on the dash when the MAF becomes faulty. Does your management light illuminate on startup and have you read the codes? What colour smoke do you have from the exhaust? Have you cleared any old stored codes before running the new maf?

[37831999]

Hi blows black smoke when idling sometimes, cleared the codes after researching the codes, thinking thus is more a faulty ECU now??? Is very temptermental! Sometimes runs fine, no smoke at all then might be sitting at a set of lights and it'll start smoking and misfiring!

[Alan M]

Sounds more like a fueling related issue which is linked with the MAF. Have you checked your fuel rail regulator? You can check fuel pressure at the rail with a gauge of some sort on the Shrader type valve. The regulators have a diaphragm in them which can become worn or damaged with use and age.

[siamblue]

I wonder if your 02 sensor is starting to fail? be careful because you will knacker the cat with the unburnt fuel,

Gary

[37831999]

If it was fuel pressure regulator it would do it all the time wouldn't it? Tonight it's ran perfect, no hick ups at all. Don't need to worry about the cat as I ain't got one lol I've now put 4 MAF sensors one so it definitly ain't that. Also found today that 8 bulbs have been taken out the dash! Not impressed! On of which was the abs light which is now one :-( the car doesnt seem to be as economical as it was, and smokes a little when boosting in first? White smoke not very dense but noticeable.

[woz]

do you want to flog a MAF sensor that is apparently OK?
PM if so - I need to get Lusty going again quick - I do 2k miles a month and thats no fun in the 1.1 Metr0)
Cheers
Woz

[Alan M]

Read your codes.

[37831999]

After changing the MAF sensor again the car is behaving a bit better, cleared all the codes and after driving only one code now comes up, 232 which i believe is PVC system? Looked at this and all pipes are on, pulled it off and no oil came out so thinking just a oil change? As now it's blowing slightly blue smoke on idle? If the oil is crap then more will pass through this system triggering the sensor ??? Just a theory lol

[Alan M]

http://www.volvoclub.org.uk/pdf/850_...Fault_Code.pdf

[37831999]

This is a very good link :-) so hopefully it is just dirty oil! Oil is black and I've planned to change it since I've had it, changing it tomorrow so will let you know the results :-) wish me luck

[hd9584]

Check the pipe that runs from the pcv on to inlet manifold (left hand side by the power steering pump). The elbow usually goes and throws up that fault code. If the pcv system need doing I would wait until it's done before doing the oil change. Do you get smoke form the dipstick tube when the car is running?

[37831999]

Erm not to sure at the dipstick, I'll have to check. Is thhe PVC system just the black box?
What's the best oil to use?

[hd9584]

The pcv is the box and all the pipes attached to it. When doing this you also need to make sure the PTC valve is clear as well. When the car is running take the dipstick out and if you have smoke coming out of the tube then the pcv neeeds sorting out. Either semi or fully synthetic 10w40 oil is best.

[37831999]

What do you do with the box and pipes? Change them? And what's ptc?

[JelT5]

You should be able to get he whole lot from Rufe @ FRF for a good price.
It's worth doing the pcv system as it can cause the rear main seal to blow, if it's clogged up. The pipe running from the box to the intake pipe on the turbo can get really brittle too.
The inlet manifold can be a bit of a git to get off- 1/4 inch drives and a couple of UJs for the sockets + a 10mm ratchet spanner will do the job though

[Alan M]

I'd have a good look over your boost hoses also for good measure as you may have a major boost leak.

[hd9584]

You renew the box and all the hoses. The PTC valve is on the pipe that runs from the maf to the turbo. It's close to the turbo end with two pipes coming out of it, one large and one small diameter. These are part of the pcv system the large pipe attaches to the box and the smaller one goes to the inlet manifold by the power steering pump.