Subaru gc8 airflow meter problems

spooner3469, Mar 3, 9:58am
Does anyone have any idea why my wrx keeps going through airflow meters! It is putting out a fair bit more power than standard and have gone through 3 airflow meters in passed 1000kms. 2 which were brand new genuine parts. is a v6 sti with the insert type. Can they only handle a certain amount of flow past them!any help would be appreciated. thanks

panicky, Mar 3, 10:01am
what sort of air filter are you using!

thejazzpianoma, Mar 3, 10:01am
You arn't using silicone or some kind of solvent or silicone thats getting ingested past them!

Could even be something as simple as having used some gasket cement or similar that is not MAF sensor safe.

spooner3469, Mar 3, 10:03am
insert type. has 2 screws that screws into plastic pipe. they dont have any codes/ colours etc like earlier models

thejazzpianoma, Mar 3, 10:03am
BTW I am not sure officially if silicone spray can get through a factory air filter, but I have noticed an instance where the owner cleaned the grill right in front of the air intake with silicone spray. The next trip out the MAF sensor failed.

spooner3469, Mar 3, 10:05am
no, only thing I have used is k&n filter oil on filter months ago, but never had a problem with that before

panicky, Mar 3, 10:07am
The oil coats the senor and make it inaccurate

spooner3469, Mar 3, 10:11am
yea, but ya would think after about 8000kms it should be fine! also have used k&n filters in all wrxs/cars ive owned and never played up before.

thejazzpianoma, Mar 3, 10:15am
Mostly an urban legend. your name suits you!
You have to really really really go nuts with the oil on the filter to have issues.

thejazzpianoma, Mar 3, 10:16am
BTW, are you sure the MAF sensors have actually been faulty and its not something else entirely thats just an intermittent fault!
How are you diagnosing/testing!

panicky, Mar 3, 10:22am
I am a reseller of K & N. I personally would not use them on vehicles with Airflow meters, only with MAP sensors.I do have one in my 3.0L Turbo Supra however and even following instructions to the T, can detect oil residue on the sensor after being run. Fortunately it is easy to clean the vortex type it uses.You wont get the problem on cars that do not have a large volume of air incoming as they simply do not suck near enough to do it.

spooner3469, Mar 3, 10:22am
Yes im sure its airflow sensors. Using the onboard diagnosis system (code 23). Have tryed plugging up old sensors and still no go. as soon as I fit a new one it goes fine. have checked all wiring to make sure there is no shorts etc.Am certain its sensor from all testing we have done on it.

spooner3469, Mar 3, 10:26am
This Is what i have come to the conclusion with. It is running mass amounts of airflow through it, with aftermarket turbo/etc etc. Just got the car into the 11s when it crapped out again.

1fordluva, Mar 3, 6:01pm
Is it killing them or cracking the the internal wiring inside the box on the afm!
Other than that you could be exceeding the 5volt parameter they use.

alltorque350, Mar 3, 6:15pm
I worked at a subaru workshop. The insert type afm does not like k & n oil on them. I would highly recomend using the factory air box with a standard paper filter. Unless you want to get a mafless tune.

spooner3469, Mar 3, 6:42pm
i havnt checked the voltage going to it yet, Cant tell if its cracking the wiring or not as havnt ripped one apart yet. Have heard about the mafless tune, but can that be done with a standard ecu! and whats the cost of getting that done!

1fordluva, Mar 3, 6:48pm
The board under the square box on the top of the afm,thats where they are prone to cracking or breaking the solder on the board inside.
Maffless means aftermarket ecu ie,link,sm4,microtech.
You are more than likely killing it with the pre oiled filter,as above try one with paper filter.
Into the 11,s is fair cracking along on a standard setup with add ons,so an aftermarket ems would be your next step.

spooner3469, Mar 3, 8:03pm
There is no square box on these airflow meters(unlike earlier models). it is just a 4pin plug going stright into meter. Have thought about going aftermarket ecu just a tad pricey at the moment, But spose it will be cheaper in the long run with afms at $250 a pop. Can moisture stuff them! As usually ran at night with cold air,Headlight etc removed for best airflow to filter.

alltorque350, Mar 3, 11:32pm
"As usually ran at night with cold air,Headlight etc removed for best airflow to filter." At night with the headlight removed!

spooner3469, Mar 4, 3:46am
Yes correct. It only needs a red tail light to meet nzdra requirements. Also when it testing it around here i remove the headlight to try and get same performance as I would at the track.

mechnificent, Mar 4, 4:59am
Have you tested the afms! With a gauge and with them installed in the car!
Have you tested them at the ecu
What do you mean by "gone through"!
What symptoms are you getting!

spooner3469, Mar 4, 7:01am
No havnt tested them like that. car runs fine then starts missing when comes onto boost,(flames etc out exhaust and wont rev above about 5000rpm when just sitting) then wont boost at all. engine check light comes on. code that flashes up is for mass airflow meter. code 23.

mechnificent, Jun 14, 1:04pm
Well straight off I have to say rhat I think oil off pod filters can kill afms.

Those symptoms do sound a lot like afm. If I was fixing the car I'd be connecting a laptop to the ecu or an electrical gauge to the ecu and checking what signal was getting to the ecu. it could be wiring. If you had a laptop connected you can see what figures you are getting as you drive.

If fitting a new afm fixes the problem though everytime, and you are sure it's not the plug with loose wires that just happen to get moved as you change sensors, then I'd be suspecting the pod filter after this many afms. Those hot-wire sensors need a nice steady airflow for accurate readings, turbulance can bugger their readings up at the best of times. Some cars will set a code just because the ecu is getting an afm reading that doesn't agree with what it thinks it should be getting according to the revs and tpi readings. The oil on the hot wire can and does bugger them too.

Have you tried resetting the ecu when the trouble shows up! If you do a reset then it goes ok for a bit, perhaps the ecu is getting confused by out of expectation readings.

Bottom line is put the original airbox and filter back in and see if the trouble stays away.