Maf Sensors Question - Any Help Really Apprecaited From A Tech Person

[Monky]

Hi all,

I just want some help to confirm that it's defo my MAF sensors that are on there way out on my GTR.

I have RB20 MAF's, they are pretty tired, have been siliconed up a few times from the looks of things before I had the car. I've managed to borrow a friends RB20 MAF so I replaced one of them, it did make a hell of a difference for a short while as before it would hesitate, it didn't anywhere near as bad when I replaced the one. The car was fine when I bought it but developed a slight mis over time which got a little worse.

In basic, if I disconnet the good MAF, the car stalls instantly which is what I am sure it is supposed to do, BUT, if I disconnet the other MAF (old one) the car doesn't stall it just keeps running. This makes me think that it's not recognising the other MAF therefore it must be faulty?

Secondly, on the power fc when I go to airflow settings their isn't an option for RB20 MAF just RB25, does this matter? The car was fine before so I'm guessing it's not an issue. When you scroll into the RB25 setting it has all the voltage values except everyone has 0% next to it, is this right?

Any help is really appreciated, I'm pretty sure I've hit the nail on the head but just want some help from you guys to be absolutely sure.

All the best,

M

[R31Nismoid]

Simply do a sensor check on the PFC hand controller - you'll soon see if one is registering

[Monky]

Sorry to be thick how do I do this and what am I looking out for?

Thanks for your time much appreciated.

M

[some_cs_student]

Plug in Power FC -> Etc -> Sensor check or something similar.

Use left/right buttons to do this on the controller from memory.

Or search for the PowerFC FAQ....

[paulr33]

choose Rb20 or Rb25 afm's is the same thing, so selecting RB25 AFM's is no problem

when you go SETTING, AIRFLOW, RB25, NEXt it should look like

0.64v 100%

1.28v 100%

1.92v 100%

2.56v 100%

and so on... The % is the correction to apply

why the f**k is yours 0??? are you sure your seeing it right?

take a photo with your phone please. if its 0% for any of them then something is horribly wrong or your tuner is a hack

if its 0 please take a photo. DO NOT change shit randomly, if its 0, leave it at 0, stop driving the car and go see a real tuner, erase and start again

[Monky]

Thanks for your kind reply.

I'm in London at the moment but as soon as i'm back i'll take some photo's or a video.

Defo on 0, i'll also do a sensor check. Will it show results for both Maf's?

Once again thanks, the car was built and mapped by RB Motorsport but before i bought the car. They are quite well known over here but regardless something isn't right due to hesitation and sounds like it sometimes drops a cylinder or two.

M

[Monky]

Hi Paul,

Am back now, here we go:

1) Sensor check - MAF 1 slightly lower voltage at around 1.0v and MAF 2 around 1.15v. Although they have voltage could the thin metal sensor be damaged in some way?

2) Airflow settings - All on 0%

The car was spot on, started developing a mis-fire, got worse and now I am here. Sometimes it picks up fine, after a little drive it starts to mis-fire and as mentioned sounds like it drops a few cylinders. I just thought it was the MAF's as they are quite messy, siliconed up and it looks like someone had issues with them before but who knows. I've never changed the settings on the Power FC and when I bought the car it pulled like a train, well it should do for 600hp!

As mentioned it was live mapped by RB Motorsports here in the UK.

Thanks for your time on this.

M

[Monky]

Sump

[paulr33]

do any of the other screen's have 0's in them?

goto SETTING, ING MAP

does it display numbers or 0's ???

[Monky]

do any of the other screen's have 0's in them?

goto SETTING, ING MAP

does it display numbers or 0's ???

Hi Paul,

Sure does, I spoke to a tuner and they said it's probably as the MAP is locked, I think this is what you were getting at.

Is is possible that even though the AFM's are showing good voltage that the sensors are buggered? I've got Z32's here, shall I go for a remap? When there we can maybe swap coils, amplifier, plugs etc and see what we come up with?

Cheers mate,

M

[paulr33]

yeah if it showing 0's then the powerfc tune is locked

tell your tuner he is a stupidhead and to unlock it

if they refuse find another powerfc tuner who has datalogit

or find someone in the UK who has datalogit and unlock it (its just a tickbox, no password etc)

then the numbers will appear

having 1.02v and 1.17v at idle across the AFM's seems fine to me

the powerfc uses the average voltage across the two AFMs

so its two tenths of f**k all difference

my suggestions

1) get the tune unlocked

2) go see a good mechanic and check the basics if you are having issues

the AFM voltages sound fine to me

if they are toast or fail, the powerfc will detect it (the voltage will go out of range)

when this happens, the engine check light comes on and stays on

and if you look etc ETC, SENSOR SW CHECK the sensor thats dead gets highlighted, with a black background

so until you see AF-1 or AF-2 highlighted in a black background and the engine check light on, the AFMS are fine

[Monky]

Good man thanks Paul. Yeah I see what you mean with the highlight, disconnected one and it did just that.

I do seem to be getting a lot of knock with the hesitation, the cat light flashes sometimes on boost. As far as I am aware this is down to injector duty cylce being maxed or high knock levels? This is why I thought MAF's were dodgy as they would cause it to run lean I am sure.

Abbey Motorsport are near me who are Skyline specialists (http://www.abbeymotorsport.co.uk/main.htm), hopefully they should be able to un-lock and see what is going on. I've just noticed I've got one OEM coilpack for some reason, the other 5 are Spitfires. Maybe this has happened before?

Well at least we are getting somewhere, 10 stars mate really appreciate your time on this ten fold great forum... I wanna send you some beer money

T

yeah if it showing 0's then the powerfc tune is locked

tell your tuner he is a stupidhead and to unlock it

if they refuse find another powerfc tuner who has datalogit

or find someone in the UK who has datalogit and unlock it (its just a tickbox, no password etc)

then the numbers will appear

having 1.02v and 1.17v at idle across the AFM's seems fine to me

the powerfc uses the average voltage across the two AFMs

so its two tenths of f**k all difference

my suggestions

1) get the tune unlocked

2) go see a good mechanic and check the basics if you are having issues

the AFM voltages sound fine to me

if they are toast or fail, the powerfc will detect it (the voltage will go out of range)

when this happens, the engine check light comes on and stays on

and if you look etc ETC, SENSOR SW CHECK the sensor thats dead gets highlighted, with a black background

so until you see AF-1 or AF-2 highlighted in a black background and the engine check light on, the AFMS are fine

Edited July 10, 2009 by Monky

[paulr33]

are you sure the CAT light is flashing?

turn the car to ON, but don't start it

the main console should light up every light (ie, in diag mode) on the dash

show me which light it flashing - is it RED or ORANGE?

the ORANGE engine check light flashes when

the car knocks over 60

injectors max at 98%

afms max at 5v

check which light you are seeing and read the PFC FAQ in my sig, to learn how to work out which one is maxing if its the organge engine check light. ive never seen a PFC make the CAT temp light flash, usually the cat temp sensor is disconneted (its useless)