*Sonic*

Did some work on a friends car today, resulting in the ECU being disconnected for a bit

once all back together, car started fine, then my mate drove away, he phoned me a few minutes later to tell me the car keeps stalling

So went out to meet him, and it was ok, and had stopped stalling

So with the engine running I unplugged the MAF sensor, the engine just idled a bit lumpy, but stayed running

On mine (same model & year) the engine cuts out almost instantly when disconnecting the MAF

I know of previous cases where the ECU compensates for a failing MAF, and after a change or reset, it no longer knows the MAF is on its way out, and can have the symptoms described above

So is a new MAF required ?

Car is MY99/00

Cheers

Steve

Jas W

Sound like it mate. My car started to idle badly. So i toke it to subaru they messed about with it and it started to cut out.

Cheesy Puff

I would say change the MAF for a new one, my one was exactly the same with a perfect tickover etc so you couldnt tell there was a problem. I replaced it and it drove much better, plus my AFR meter started to make proper readings too. Well worth doing every year.

Cheese.....

Gidney&Knowlesy

MAF needs changing very fragile these things & one of our quickest stock shifters

Dark Blue Mark

If he whinges, you've actually done him a favour in detecting it

MB

Cheesy Puff

Think I tempted fate joining in on this thread, just gone out in scoob this morning and all sorts of funny readings from AFR meter. I unplugged my MAF and my car idles perfect again, so it would seem my ones buggered tooo.
So a trip to my local dealer comming on this week me thinks and a few days of very carefull driving, any where I can buy one online?

Why are these things so bloody weak, I know Im running an APS/K&N filter but I was led to believe after carefull research that the K&N filters are more friendly to the MAF than some others.
The sensor itself is spotless so I dont think its been contaminated with dirt or oil, so why did they change to this weak design as some VWs use a similar part and suffer the same.


Cheese....

Dark Blue Mark

Vibration can kill it too. Is it APS or K&N? APS are very bad with MAF's from the evidence on here.... Does yours have a bracket holding the filter onto the engine bay?

Some are using the MAF from a 200SX from memory, but dont know about fitting issues...

Xtreme sccobies or Power Engineering will get you one, or your dealer.

MB

Cheesy Puff

hi mark

Yes my APS cold air kit is bolted to the inner wing where the original airbox is bolted, the metal tube then goes out under the hole into the wheel arch to get cooler air than under the bonnet. It then has a K&N cone on the end, its the newer one that alows you to keep the original MAF housing (the MAF used to fit directly to the older type needing a remap because the diameter is bigger).
I may try swapping my Lambda first though as I have a spare one, I say this because Ive just tried unplugging the MAF while the engine was running and it cut striaght out which I believe is a sighn that the sensor is still workin.
Maybe my cheapo Halfrauds Lambda is just reading bad, will swap it tomorrow and let you all know.

On a side note been out with a mate today as he was buying an Audi S4 and we looked on a couple of forums and what do they suffer from? You got it Bosch MAFs, and they look very much like our ones fortunatly for Audi owners they changed to Hitachi MAFs instead.

Cheers
Cheese...

Bowders1

It must be time of the month.

I have a 94WRX Wagon

I thought my Maf was on its way out , but I too unplugged and stalled instantly???

Signs are :

Car starts up fine after about 5-10 minutes the car starts to run a bit lumpy like a plug is splutering. Changed Plugs to PFR6B about 2000 miles ago (gap 0.9) so would not think these were the problem.

If I drive the car harder it seems to correct itself then start to come back on driving low speed and low revs again.

Any pointers would be appreiated.

Mark.

Dark Blue Mark

Cheese, as you say, the K&N is pretty well proven and seems a good setup. The APS cold air feed is a good idea, and not the cause of any probs.

Yours might be the lambda too Mark, given it happens a few mins after starting the car. The lambda has a heater on there, and the sensor only kicks in when this is warm. Could equally be the MAF, but I would look at the lambda too.

Is your MPG poor, and is the tailpipe quite sooty?

MB

Winders

The fact that you notice a change whilst unplugging the MAF shows that the MAF is at least doing something, more than likely it is your lambda sensor. You will find once you change the lambda sensor then reset the ECU, unplugging the MAF will result in a stall.

Winders

Bowders1

MB,

The MPH is around 170 miles on 30 quid. This has not really changed since I had the car 6 months ago. The Problem really only started around a month ago. The back box is quite sooty though. I thought these cars tend to run a bit rich...

appreciate any feedback.

Thanks

Mark

Cheesy Puff

Must be my lambda buggered then I only get about 80-100miles out of £20, so I think mine is rich and yours is lean by the huge difference.

Cheese.

Dark Blue Mark

They both sound a bit juicy, but depends on the car...

UK, WRX, and STi MPG's do vary a fair bit between cars. My UK99 used to give 280 miles to a tank and the STi4 on the same route would give 220 miles.

Its a bit difficult to say, but I would say yours is quite rich Cheese. What car is it?

Mark, yours sounds about ok to me. The car is designed to run a bit rich, for safety sake so the tail pipe will be a little sooty, but quite black is always a sign of too rich.

I still maintain it saves money to change these things every 18 months on MPG savings alone.

Definitive way is a RR test or Delta dash readings etc, but a bit pricey just to prove the Lambda is dead

MB

Bowders1

Thanks Mark.

My driving is lots of stop starting and local trips, so was kinda expecting to be a little low down compared to some distance driving.

I think I will change the Lambda sensor and then rule that out, based upon the money.

Do you know what type the a 94WRX Wagon takes??

Thanks

Mark.

olliecampbell

iTrader: (3)

Oh dear, wish i didnt read this thread as well!

MY00, and i seem to have the same problem as Bowders1, slightly lumpy, as if 1 cylinder doesnt fire properly, sooty tail pipe.

Going to give the MAF a yank this week and see if she stalls.

Is there an easy way to test the lambda?


Its running an ITG, yes i know i should change it!

Bowders1

Ollie,

Bloody nightmare is'nt it...

The strange thing is that most people who have been in the car don't notice it. Makes me feel paroniod.

I had an ITG in my car. It ran crap . and you must of read the many threads on Maf failing.

I changed mine for a K&N induction kit and the car was transformed. The filter looked clogged but that's how it was from new???

I would be interested in what you find after the maf change as I have just ordered today a lambda sensor. Let you know when I fit it.

I am also going to recheck the spark plugs (only 3 months old) and may change the gap size from 0.9 to 0.7 to see if that helps running.

How long have your symptoms been running for. Be interested to know what history of the problem is.

Mark.

olliecampbell

iTrader: (3)

Yeah it is, russian roulette (sp??)

Hmm im not sure ive only had the car for nearly a month now. Ill give the MAF a go this weekend (ultimate street car), i was thinking plugs as well.

Whats the deal with the gap change? weaker spark?

Im looking for an HK panel filter to replace the ITG which ive heard is renowned for MAF failiure!

Bit of a project, but very fun all the same

olliecampbell

iTrader: (3)

Right ive just tried the unplug the MAF whilst its running trick and the revs dropped, but it ran but very very lumpily.

New MAF? Should it outright stall or is really bad, only just running what it should do?

Cheesy Puff

Right guys mine seemed to be my Lambda this time around which is a bit of a result, mind you it still cost me £45 as Halfrauds is all out of £25 jobbies.

My AFR meter and Turbo timer (linked to Lambda) were both showing leanish readings and were a bit irratic to what I was used too, looked very similar to MAF failure last time.
I would suggest you get some type of AFR meter if your in 99/00 models, but worth doing the unplug Maf test to check also as the AFR meter reads the standard Lambda and could read incorrectly giving false readings.

All good stuff though if it wasnt for forums like this I would have listened last year to two Subaru dealers who said my MAF was ok, and would probably have a useless pile of bolts on my drive at the moment due to a buggered engine.


Got to say my Apexi turbo timer is very good giving the Lambda voltage and theoretical(sp?) air/fuel ratio, most useful

Cheese..

Dark Blue Mark

Subaru dealers are ****e, I think they're trained to not have a clue about MAF sensors.

MB

Bowders1

Ollie,

I woould go for the Maf as if it still ran although lumpy means the maf is not doing what is is supposed to and i belive from quotes on this site that the ecu is trying to compensate.

If Maf was working as it should you would definately get an engine stall.

Agree with cheese that it is worth getting some monitoring devices, and this site is a dogs for getting info....

Can you guys give me a best to go for on a Ltd budget.

ie knocklink, etc.

cheers

Mark

skydiver

Hi Cheesy Puff
I use also the Apexi Timer but i think the readings is not accurate.
I have seen that on a dyno at the time when adjusting a AFC (12.5 in wideband lamda for 13,9 TT readings).

Cheesy Puff

Hi Skydiver

Think your right about the Apexi not being 100% accurate, but does allow you to see if anything is different than normal a bit like using the same scales to get your weight if you get what I mean lol.
I think you can set the values on the timer to be closer to the real figures but would need something to set it against, I also have an Autoguage AFR meter in my centre pod which is more of a guide of "not normal behaviour".

I would like to check my Apexi against a real instrument to see how good/bad it is, better probably to set it to Lambda voltage as surely it must read these pretty close?

Its good here isnt it!
Cheese.

olliecampbell

iTrader: (3)

Are you sure its that way round? Is it definitely supposed to stall, or run lumpily, im getting confused!

Ollie

Trebor69

Hello All

I have a couple of fully working MAF for classic impreza (one on ebay at mo)

Just had a gems fitted so don't need em..

If your stuck I could possibly lend you one...

Rob

olliecampbell

iTrader: (3)

Thanks for the offer i may take you up on that, just want to do the test first

How come the GEMS doesnt need a MAF?

Trebor69

No probs mate, Just PM me if you need help!

Gems Ecu's use tha MAP (manifold absolute pressure?) sensor instead of the MAF.

They work out how to fuel differently than standard ECU.

Just had it fitted today and mapped.... 343BHP 332LB Torque.. Boy was I smiling ;O) ... Anti lag is silly, pops and bangs and flames galore from exhaust..

Rob

Adrum

Im rubbish - whats a MAF, cause ive just put the OEM air filter back on and its dropping revs on idle and the CEL is coming on - could this be the MAF.

Please enlighten me!

olliecampbell

iTrader: (3)

Dont think it is the MAF now, just needs a service. The lumpy idling happens from startup, and it idles very badly when i pull the MAF out, which is what is expected i believe.

Thanks for the offer thought Trebor