m@t STImulation

iTrader: (3)

what is the cause of the maf sensor failing and what are the symtoms of a knackered 1??

happydude303

iTrader: (1)

maybe a bit of hunting what year is yours has as have a spare maf sensor for a late 97

legacytt

start car disconnect maf if car stalls then your maf is fine if it still runs then possible maf knacked

Saalro

iTrader: (8)

When the MAF went on my VW Golf it was causing poor idling, cutting out and poor response, but only at certain times, one moment it would be fine then another it would be having them problems. I unplugged the MAF when the idle was bouncing all over the place and then the idle went back to normal, i then plugged it in again and it started running rubbish again. That's how i found my MAF was broken. Thought that might help even though it was a VW, surely can't be too different!?

t7srt

iTrader: (2)

Not true I'm afraid, All that will do is premeturely damage a good MAF, Its hot wire so as you pull the plug its not getting heated anymore, gets cold very fast and damages it,

There are many symptoms of MAF failure, some can idle funny through to not running at all, The only way to check for sure is to use the diagram below



With a multimeter you can check the input signals to the ECM, On idle you should get -1 volt from the green wire, any difference from that and its most certainly a damged MAF.

Hope that helps

Splitpin

With due respect Legacy, that advice is not correct, it is not a reliable way of determining the health of the airflow sensor. By that method you could easily chuck out a good one or leave a bad one in the car - and as T7 says, it won't do the health of the sensor any favours either.

m@t: There are a number of possible symptoms and you may have to use more than one. Hunting idle after an ECU reset is one indicator but it too is not 100% guaranteed to pick up a degrading sensor. The key symptom is erratic or low sensor voltage under boost - which leads to lean running. This will initially make the car feel faster as the leaner mixture will give you more power. However beyond a certain point it will also lead to detonation, which will get worse and worse.

The more information you have available, the easier it is to spot something like this in the early failure stages. If you have an AFR meter, especially a wideband, you will notice the leaning (and probably erratic) mixture under boost. If you have a Knocklink, you will notice an increase in activity.

About the only way to be cast-iron certain is to bench test the suspect sensor. In practice, you can do it in the car by datalogging the sensor voltage under boost, swapping in a new one and then repeating the datalog under the same conditions. If the old and new sensor voltage profiles are the same, then the old one is good and can be put back in the car. If it's lower, or spikes up and down despite steady boost pressure and increasing engine speed, then the old one is knackered and should be thrown.

my94wrx

iTrader: (4)

this is what i did a presumed my maf was dead, the only way to properly test a MAF is read the voltage and make sure that it is within range

my94wrx

iTrader: (4)

not necessarily correct for the year of the OPS car, the OP needs to consult the manual to find out what the voltages should be.

m@t STImulation

iTrader: (3)

alli know is it cae u on th cuucodes about 3months ago inored it as thcar wasin the garae fo most of this tie haing work doe im having an apexi pfc fitted on the 18th and the maf will need to be 100% working order for a correct map to be achieved. some people have mentioned upgraded MAF i have a green lable one at the moment i will replace like for like unless im told of an upgrade from a reliable source

legacytt

im only going on whats been tried on here in other threads to establish a possible maf failure and i cant see the maf being damaged for the sake of a few seconds but there we go as for checking voltage at the maf do you need to disconnect it first.

my94wrx

iTrader: (4)

no i connected a volt meter at the ecu end of the maf signal and measured the voltage there as per the manual, and this is the only way to check if the MAF is in "spec"

legacytt

cheers for that i really need a manual.

my94wrx

iTrader: (4)

your welcome! as for the manuals here you go https://www.scoobynet.com/technical-...w-updated.html