Help needed, MAF sensor problems?

[mar_k]

I have been helping a friend with his 1.8turbo golf mk4.

He brought it round to mine as I have VAG-COM,

He had 2 lights on the dash, The emissions control light and the EPC.

I scanned the car and it showed MASS AIRFLOW SENSOR (G70) low reading,
I cleared the codes and scanned it again but the same fault was showing.

I got a new Bosch MAF and fitted it for him, then cleared the codes and both lights
went out and stayed out.

I re-scanned it and it was clear, no faults shown.

Its been running fine almost a week but now both the same lights are back on
and I scanned it again today to be greated with the above fault.


Mass airflow reading to low.



What would be causing it to knock out a new genuine Bosch MAF in just under a week?
And what does the EPC light have to do with the MAF?


any helo is appreciated

[bobbieboy69er]

Can happen, i went through 3 in as many months!!  now nothing for about 10 months.... touch wood!

Make sure the housing is secure and its not rocking/banging around under the bay, that can make it faulty

[xxChrisxx]

I really wish people would get rid of this myth that it's always the MAF.
Bosch are ISO 9001 certified, which means they have a QA system in place and use it.
They simply wouldn't have that many defective parts going out the door.

When you change the sensor and reset the codes you are resetting any learned values that the ECU has.
Thus if it's a sensor problem, it runs fine until the system re adapts to learned values. When this happens the problem returns.

It could be a wiring fault, it could be a massive leak somewhere.
If you have a poor earth, it could be causing a short.
It's not beyond the realms of possibility that you have a duff, but it's more remote that people would have you believe.

Stick a volt meter on it to see what you are getting.

[conor1]

surely if the new maf went faulty in such short time you went get a replacement right.

[Wayne]

surely if the new maf went faulty in such short time you went get a replacement right.

Depends on why it failed, if it is faulty then yes they will replace it but if something else is causing the problem then not much chance they will help.

[bobbieboy69er]

I really wish people would get rid of this myth that it's always the MAF.
Bosch are ISO 9001 certified, which means they have a QA system in place and use it.
They simply wouldn't have that many defective parts going out the door.

When you change the sensor and reset the codes you are resetting any learned values that the ECU has.
Thus if it's a sensor problem, it runs fine until the system re adapts to learned values. When this happens the problem returns.

It could be a wiring fault, it could be a massive leak somewhere.
If you have a poor earth, it could be causing a short.
It's not beyond the realms of possibility that you have a duff, but it's more remote that people would have you believe.

Stick a volt meter on it to see what you are getting.

He said it was the MAF because the code it threw was Mass AirFlow reading to low.  Therefore it is safe to assume its a MAF related problem, not necessarily the sensor.  Not such a Myth afterall.....

[golf-sib]

Measure the maf gs values by logging this will aid in what's the issue at hand, could be a leak that sometimes sets it off from experience, the ESP could be lighting up as of a n112 fault possibly as well. Or a short/ground issue is present.

[xxChrisxx]

He said it was the MAF because the code it threw was Mass AirFlow reading to low.  Therefore it is safe to assume its a MAF related problem, not necessarily the sensor.  Not such a Myth afterall.....

The mere fact the problem has returned shows that changing the physical sensor did nothing.
The next logical step is not to assume the new one you've got it duff. It's that you've got the diagnosis wrong, and further investigation is required.

There was another thread recently where someone has been having issues, pulled the MAF to see if it ran worse then got it scanned. Lo and behold a MAF fault.
People pull sensors, reconnect then and then forget all the time. I've had shorts in wiring give MAF warnings before.

The fact it's thrown the same code means it probably is something on the MAF circuit, so my guess would be a harness/wiring fault.
Ideally you'd do a log of the mass flow, but short of that a voltmeter will indicate a good or bad sensor.

[mar_k]

I took the car to my mate who is a workshop manager at a vw dealer,
They hooked the car up to their diognostic machine and was told by his master technician that
its an air leak some where but he didn't have the time to investigate further.

We was advised to get the inlet off and replace the gasket and check all the pipes for signs of perishing,

He also said there is a 1 way vavle in a pipe on the lower part of the inlet that can often fail.



Was impressed with their machine, no wires, just a bluetooth plug that plugs into the diognostic port in the car.

[Bandit127]

I took the car to my mate who is a workshop manager at a vw dealer,
They hooked the car up to their diognostic machine and was told by his master technician that
its an air leak some where but he didn't have the time to investigate further.

We was advised to get the inlet off and replace the gasket and check all the pipes for signs of perishing,

He also said there is a 1 way vavle in a pipe on the lower part of the inlet that can often fail.



Was impressed with their machine, no wires, just a bluetooth plug that plugs into the diognostic port in the car.

Something like this? £10 off ebay.
ebay clicky

I want one. Plus an android app called Torque and you can have live logging of all sorts of data (including bhp) clipped to your dash. 

EDIT - maybe it was actually this? A bit pricier but looks more like VAG kit.
another ebay clicky



Common MAF faults that aren't actually the MAF are (as you have found) a leak in the inlet and oil from an aftermarket filter getting on the sensor.