Hello, just wondering if anyone can help.

Ive got an STI ver 5 with an API 2.5 conversion. The MAF has gone twice in 2 months! David at API says it could be to do with a faulty supply or earth as it runs on millivolts and very sensative. Unfortunately he hasn't got the equipment to diagnose this, it's more main dealer stuff.
I phoned the local main dealer who won't touch it as it's an import. Can anyone help or suggest someone who can help? I live in Romsey nr Southampton so as local as posible.
Many thanks, Loz

 

Did you buy a new MAF, with a green-dot on it? I've never known one of these to fail - either through gradual deterioration or from excessive vibration. If running a cone, ensure it's bolted down so it cannot vigrate or bounce around too much.

Secondary question: how do you know the MAF has failed? Did it cause a big bang and heart stopping moment as the engine instantly dies, or is it 'just' a check-engine-light? I assume the 2.5 conversion included some sort of remap - on the stock ECU, or aftermarket?

Richard

 

Try len at www.subaru4you.co.uk you will find his numbers on there, hes an ex main dealer machanic, loves the imports.
hes based in newbury just down the a34
sure he will help.

 

The GC8 maf is powered by the 12 volts rail, the output is independantly powered by the 5v rail so hardly millivolts, the output range available and fed to the ecu is 0 to plus 5volts. Are you are running with the stock airbox and a panel fliter that is not full of gunge ie STi, std or K & N type ? As suggested have you been supplied with the latest version that has the green stripe ?

bob

 

Hello Bob, you were my next port of call! Cars booked in for a map with you at the end of the next month. Running a HKS power flow. The MAF has a green stripe on the top. The car has been running the Sti 5 ECU for the run-in awaiting re-map which was oked by API. Any ideas? Help appriciated, Loz

 

Shows how much I know about that strange electricity stuff !! Now I know why my family duck when I change a light bulb......

David APi Engines / APi Impreza
www.apiengines.com

 

Loz;

One of my mates had a HKS pwer flow filter, and had MAF's constantly dieing.

We replaced the MAF and cleaned all the pipework one week, and a month later, the MAF was covered in cack, and the pipework was full of the same cack - it looked as though the filter had not filtered well at all! On searching the Web, it appeared that the HKS filter was not famed for it's filtering abilities (second worse to the Blitz mesh one). I would say that the cack was either destroying the MAF, or buggering up the readings (but who would be confident that a clean would cure the problem totally and not lead to lean running etc!) On a race car this is not too much of an issue as parts are replaced/reconned after every meeting, a road car however needs more longeveity, and I wouldn't personally use a HKS filter on my car.

I have a bespoke K&N item on mine, and have had no problems in the year it has been on (incidentally this is what my mate now has and he has had no problems since the change either).

FYI, I had an ITG panel filter on before, which wiped out a MAF, so it is not strictly due to induction kits.

 

API David, you are partially correct when you say the sensors work on millivolts, the airflow signal is only dropped by millivolts when the mafs fail but a 50mv drop in signal can be the difference between a sweet running engine and a melted one
It would be a better option if the sensor did actually lose its 5 or 12 volts as the car would just cut out totally rather than just run dangerously lean with advanced timing.

Andy

 

My last MAF has lasted 12 months ... now the voltage output is slowly fading ( as noted per DeltaDash) . Std Airbox / Dry Panel filter . Was a new green spot MAF from the dealers....

<sigh>


Steve

 

Just had a similar experience to Tonyflow with an HKS Powerflow on a 98 UK car. Was very concerned to see the apparent lack of filtration.

 

The HKS powerflow is the worst you can buy.
Here in the netherlands several maf's died wit this induction kitt.
Buy an Apexi and you have the best filtering and flow.
I've ran an Apexi induction kitt and had no Maf faillure's at all within 9 months/20.000km

 

There used to be a page (think it was from a Toyota TT Club) that compared filtration by attaching filters to a vacuum, and pouring dust over them, IIRC, the order (from best to worst filtration)

Doesn't matter - found it now http://www.mkiv.com/techarticles/filters_test/2/

 

A friend went through 3 MAF sensors thanks to the HKS Powerflow filter (although he had done high miles on a secondhand filter, so who knows when it was last changed)

Either swap it for something else, or at least change the foam filter and ensure there is not much movement at the filter.

The general concensous is that it's one of the following:

1) Bad filtration
2) Vibrations to the MAF sensor caused by bad fitting of filter
3) Dirty foam filter

 

Thanks everyone, I shall look into a new induction kit before fitting another MAF and remap. Think I was just unlucky. Have recently fitted a new filter element. Any chance it's because of the new bigger bottom end some how? Managed 32000 miles before one went then 2 in under a month. Does anyone do a more hard wearing one or do I just have to grin and bear it? Cheers, Loz

 

As little as 10 mv can make the difference dependant on where you are on the map at the time let alone 50 unless a decent afr margin has been mapped in.

If you want to fit an induction kit the the K & N 57i seems to be good, I've used one without any issue for some time now. Be careful which Apexi you use if going that route, do not fit a stainless streel type, that has virtualy no filtration at all. the alternative type I've seen seems to lack filter area but agreed it hasn't the reputation for allowing maf's to get into trouble.

bob

 

do any induction kits replace the MAF Housing? What diameter is it?