I've joined the "Anals".
 

Yes, I've fitted a new MAF sensor to my September 99 UK Turbowagon.
Only 31K miles too.
Now, the new one is different to the original in that the original had two small vertical metal posts on the top surface. The new one doesn't. The new one also has a green line on the top of the mounting flange edge.
The really interesting thing though, is that although there were no signs of MAF problems, (I don't have any extra instruments though), as soon as I tried the car it felt much more sort of eager. Somewhat like when you fit a new set of plugs but more so.
Then a longer run a few days later really reinforced the feeling with the car just seeming to say "Come on let's get going".
My imagination? I don't think so as the difference was so noticeable.
Only other thing done at same time was an oil change and never noticed any difference after that before.
Hmm, interesting.

Interesting indeed, you did carry out a ECU reset didn't you??

Pete

No.

Couldn't have been the MAF then as the ECU is still operating under the same conditions it found itself in before.

I think you are deluding yourself - you MUST reset the ECU!!

Pete

Is re-setting the ECU as easy as leaving the battery diss-connected for an hour or so? or will it gradually reset itself?

I have an 02 WRX with de-cat and induction kit, do i need to get it re-set, or are the classic ECU different to the classic ones.

Thanks guys

Cookie

I think Classics are different

Pete

Surely the MAF just supplies values for the ECU to use?
I will try a reset though to see if there is any change.
I've never bothered to do a reset even when I changed to Optimax at about six months old because I found the Optimax made the car run more smoothly and ironed out a hesitation from first tankfull.

I'm sure that I have been told that the ECU realises the MAF is out of tolerance and inputs its own values. I'm not sure it would take any notice of the MAF without a Reset?

This is what I have seen written here ......

Pete

I'm pretty sure an induction kit killed the MAF on my 02 - just glad I found out before any serious damage. ECU was reset by the chap who remapped it - don't think there is any other way.......

Went back to standard airbox and STi filter. Knocklink has been dead ever since :)

Yes, but then should you not get a Check Engine Light because the ECU is in "limp" mode?
My understanding from what I had read, and I stand to be corrected, was that the MAF could become "lazy" and then values were wrong but ECU didn't realise but used them.
I can see that a "dead" MAF would lead to the ECU using stored "safe" values but that would activate CEL surely?
Btw standard airbox and filter from new.

ECU on the MY99/00 is a "fast learning" one - you don't need to reset (as per the connectors under the steering column).
The ECU will reset very quickly - within a few miles.

But, I tend to agree that it could be a little bit of column "a" (new MAF), and a little bit from column "b" (placebo effect!!)

That's what you call "sitting on the fence"!!! :D

Dan

edited to add

Not going to get back into the MAF debate (Pete ;)), but I had several MAFs die (one causing serious engine damage, but paid by Subaru!).
NONE of them triggered ANY alarms on the monitoring equipment.

Yes, a FAILED MAF will show up, but a faulty one won't (doing almost as much damage) - that's why some people (myself included) change them as a serviceable item, as they're only £78. The MAF is a well-known achilles heal of the MY99/00.

This 'lazy' word amazes me .... I assume that it means the MAF has gone out-of-tolerance?

If thats the case then the ECU should detect if it has drifted out-of-bounds and input its own safe values.

Some say that the ECU isn't robust enough to do that - which is a convenient statement.

I would say that a reset 'should' be done to just have a good old clear out ........... but what do I know? I think most of the ECU/MAF thing is poppycock anyway!? ;)

Pete

Pete, You are correct to a point. The MAF can drift and read low but still be in the 'envelope' as it were. The danger is that the engine is now seeing more air than the MAF is telling the ECU. The engine runs leaner and if the car is driven hard in this condition then det can be caused. Evereything heats up and the piston expands too much etc...

F