john banks

As I understand it can look fine but be damaged.

If you want me to help you with yours SCOSaltire I can do that no problem. It is a quick job, but it depends on what bit you get. The sensor only sounds a bargain!

I would reset the ECU after a faulty item is removed personally and let it relearn, but it possibly is not necessary.

[Edited by john banks - 5/2/2002 2:25:09 PM]

WREXY

Hi peeps,

Just changed my MAF sensor cause if you would have seen my Delta Dash logs, you would have seen that my mixtures were leaner than other MY99/00s, here, http://www.scoobynet.co.uk/bbs/threa...d=90011&Page=3.

I must say that the MAF I have replaced did not look contaminated and it still looks very clean and the metalic bits inside look nice and shiny. I don't know if that's an indication of a good MAF or not. I won't be testing the scoob till Saturday when I do an oil and filter change. I'll know then if the MAF was faulty or not

Do I need to do an ECU reset? The ignition was off while I was doing the whole of the replacement procedure.

Cheers,

Wrexy.

SCOSaltire

ill be interested in what u find...

how did u take off / put on ur maf?
id like to do this... asked the ng before... but i need *very* detailed... read dumbass... instructions

WREXY

Subaru Greece now sell the sensor seperately to the whole MAF housing and it is much cheaper than buying the whole thing. Cost was 90.00 Euros which is 55.60 GBP.

Replacing the MAF is easy. Undo the four bolts that hold the housing to the airbox and then undo the one big hose clamp which is to the right of the housing. Pull housing out and unclip the wiring rom the MAF sensor. Then undo the two screws which hold the sensor into the housing and pull out. Reverse the procedure to install.

Note that the two screws which hold the MAF sensor to the housing need a special tool to undo cos they are a funny looking screw. I broke off the two little nipples in the centre of the screw and used a hexagonal screw driver to undo them.

I still need to know if I need to do an ECU reset or not. I'd rather not do one if it's not necessary cos if I do a reset, the ECU will have to re learn the knock correction.

Cheers

Wrexy.

PS On Saturday, I'll let you know if it was the MAF that was the problem.

WREXY

Cheers John.

I'll do one then.

Regards,

Wrexy.

mutant_matt

Wrexy,

The UK dealers have started selling them for Ł60 for just the sensor bit now as well

I don't think you need to do a Reset as the ECU didn't think there was anything wrong before. If there is some "learned" knock correction, it would be quicker to reset it but a couple of tanks later, it will be back to the same place - it's up to you really.

Matt

WREXY

Cheers Matt,

It may be a good idea to stock up on a few MAFs now that they're cheap and in case Subaru change their minds again.

I was told by Merv from PE, that the new batch of MAFs for the MY99/00s are better than the first lot. These ones have two green dots on them. One near the top of the sensor and one near the bottom. The MAF I replaced, which was the MAF on the car from brand new, had only one green dot near the bottom. Merv said that he had not come across any cars with a faulty MAF that had one of the newer MAFs installed.

Cheers,

Wrexy.

MattRus

Just replace the MAF after total failure (see MAF _cost? thread).
Cost Ł286 - ouch! It was the complete assembly, bit silly really because one only needs the sensor whcih is easily removable with the correct tool. The external appearance was perfect, appears that the internal electronics fail. Incidentally tapping the sensor body caused a signal change so the failure in my case may have been mechnical (bad contact?).

WREXY

MattRus,

I just read the thread. You must have changed it today then. Why didn't the dealer tell you to just buy the sensor? I wonder if you could go back and complain to them.

Cheers,

Wrexy.

EvilBevel

Hi Wrexy

Welcome to the club of broken MAF owners...

I have about 3 on the shelve now ... 1 sensor only and 2 sensors with deluxe tea-strainers.

Good info on the price of the sensor only though... I just got billed 420 EUR for a second hand MAF (that was broken as well ) The fact that I have to pay 1.400 EUR for express delivery to Spain didn't make it easier to swallow ...

Of those 3 broken MAFS, there's nothing visible. Cleaning doesn't help at all, so it may be an electrical failure.

Funny thing is, these sensors fail a LOT more often on VW TDi cars (and Seats etc...). And yes, they are the same sensor, just with a different wiring plug.

I'm now on my 4th MAF sensor, and have ordered one in reserve (to go next to the spare bulbs).

Anyhow, I'm not an expert, but in my case the ECU was reset after fitting a new shiny MAF, with no ill effects (according to DeltaDash, a product that I can *heartily* recommend to any serious Impreza owner... I think you may agree )

Also... very good info on the "new" 2-dotted sensors... can anyone else confirm this ?

The more I read up about MAF's (and the way they fail, sometimes gradually) ... the more I'm thinking about a MAP based setup

Thanks,

Theo

yorkmeister

I took MY99 (34000 miles)(6month service) in to Ace Kensington the other day. I had put an ITG filter in about 1000 miles previously (and an SS backbox). The engine was idling badly but I didnt mention it as I wanted to see what they thought it was.

They gave me the car back that afternoon annd they had replaced the whole MAF sensor thing (Ł260 odd)under warranty.

They also replaced the (1st) clutch under warranty that day due to clutch judder and I am happy to say it seems to have cured it.

The car is now running fantastic.

mutant_matt

Sorry to go off topic but, THEO, where HAVE you been m8???? Good to have you back!!!!!!!!!!!!!!

Matt

EvilBevel

Thanks Matt Just took a break from it all for a while.

I'll stick to Drivetrain from now on though ...

WREXY

Hi Theo!

3 MAFs!!! My goodness! No wonder all these scoobs are blowing engines.

Thanks for the info, on that there are no visible signs on the actual MAF itself. Makes me more confident that it is my MAF causing the slightly lean mix. I have decided that I will do an ECU reset. The ECU will learn again.



Theo, I agree about the Delta Dash. It's what showed me I have a problem. I reckon if I didn't have it, my mixtures would have got more lean, which would have resulted in some serious damage to my engine. I had no idle problems, so was unaware I had a problem. I was lucky I bought the Delta Dash when I did. Actually I was more lucky that Dave and Merv from PE came to Greece to do some serious mods to an EVO 6 and Stephen Done e mailed me to let me know they were here, with a Delta Dash. We organised a meet for me to go check the Delta Dash out, on my car and I liked it that much, that I ordered one and paid for one right there and then.

LOL at the 2 sensors with deluxe tea-strainers.

Cheers,

Wrexy.

john banks

Theo I was thinking about you this afternoon and wondered WTF you had gone and was going to email you!

I noticed whilst doing my plugs this afternoon that my MAF only has one green spot. Oh well. Spare might be in order to keep with the brake pads, lambda sensor, gearbox, clutch and big end bearing

EvilBevel

>>Theo I was thinking about you this afternoon

Only good feelings I hope

Spares... yeah, I'm on my third gearbox now as well Mind you, both in case of the MAF and gearbox, they are mostly my fault... (remove resonator: 2 MAF's, fit PiperCross, one other MAF, being less than versed in track driving: 2 gearboxes).

Still love the car though

Theo

john banks

WREXY, looking at my Delta Dash logs I see a pattern building up - when it is cold at night I get lambda voltages of about 905-910 mV. During warmer conditions during the day I get 890-900 mV. During a hard thrash that can go down to 880 mV. Hope this helps.

Gazza_W

Hello Everyone

Can I join the MAF failure club too !!!

Car just suddenly loss the performance gradually so I
took it in to the main dealer last week .. (my car is a 1997 catalunya turbo model)and said that my MAF has come up on the select monitor.

So what exactly does a MAF failure do to the engine ?? Can it cause any damage if it's not sorted soon ??
What are the main symptoms of a failed MAF sensor ???

Cheers

Gary

WREXY

Hi John,

So maybe the Greek hotter conditions are causing the lower voltages?

To do my logs, I start the car from cold, let it idle till it reaches 750 revs from the 1500 it starts with, then I drive for about 5 minutes at around 40 miles an hour till I get to the stretch of road I do my logs on and then I nail it in second, third and a bit of fourth gear, till I reach around 95mph or 150kph. I run out of road then. Ambient temps are around 25-26deg celsius.

Gary,

The MAF can cause damage to the engine when faulty. The symptoms are, (not always all of these), uneven idle, running lean which can destroy an engine, loss of performance.

Cheers,

wrexy.

mrkimpreza

Remember my engine failure (hole in piston). The car is now repaired and I drove it in with the original MAF. No problem, it's runs perfectly.

Then after the run in period we put in on DeltaDash and Select Monitor and give it a go at 7000rpm with an old and a new MAF. Old MAF was reading max 4,1V, new 4,3. With old MAF o2 was .83-.87, with new MAF os2 was 0.9-.93 and injector duty cycle was higher to and knock correction was less. Needless to say that I now drive with a new MAF :-)

Here are the screendumps from DeltaDash:

http://pub1.ezboard.com/fsubaruclubmotorisch.showMessageRange?topicID=385. topic&start=81&stop=83

What bothers me is that a few days ago I gave it a go in Germany at 5th gear and at full load at 5000-5500 rpm I saw o2 values below .9 (.88). Should I worry ???


Mark.

dowser

Mark,

When the o2 sensor gets hot it under-reads - remember, the ecu only uses the lambda at lower rev/boost levels to maintain optimal mixture for the catalyst. Once you're on full chat it's reading data from the map dependant on input from other sensors (MAF included ).

Richard

mutant_matt

Mark,

That URL doesn't seem to work.....

john banks

That was one serious amount of knock correction on the old MAF. I get only -1.5 degree spikes lasting 0.1-0.2 seconds possibly about twice in a five minute log. You were getting >4 degrees retard lasting continually for 5 seconds or so. 900mV does not seem that lean?

SCOSaltire

john
what were the logs from the run in my car like... compared to others here

the car is definatly running smoother..
the most noticable difference is at idle just after switchon when cold...
its rock steady at 1500 rpm now...
and as it warms.. gradually lowers itself...

used to waver from 1300 rpm to 1800 rpm...
thats a big difference...

my daily passenger has commented on how much smoother the car is..

john banks

SCOS your logs were fine, trivial knock correction and plenty rich
enough. Looked perfect after we cleaned your MAF - we did not log before of course.

WREXY - I wouldn't want to say any continuous knock correction - the maps seem quite conservative over timing except at about 5000 RPM, and then I am putting in massive amounts of extra airflow and see very little retard at all. Fuel ? possibly. Dodgy injector? Low fuel pressure? Lots of possibilities?

mrkimpreza

I'm always using RON 98 fuel. Best you can get in Holland.
Subaru NL said my MAF was gone due to the fitted K&N 57i induction kit and consequently blown my engine, so no warrenty whatsoever.

I did not believe this so I had the engine repaired with the old MAF (and had the injectors etc. checked), the standard airbox, run it in and wanted to graph old MAF against new one to make a hard proven case to Subaru NL....**** happens. The old MAF did seem broken. Now I'm waiting for the official letter from SN and will try to sue K&N, which is a bit harder I think :-((((


Mark.

WREXY

Mark,

Thanks for the info m8! Good luck and I hope you can get your case sorted out.

Cheers,

Wrexy.

JIM THEO

And I am worried about my 0,5-3 instant knock correction between 4200-4900 rpm! Yours Mark is tremendous!
By the way, today “lights up” the 5th light (RED) from my knocklink sensor in a quick blast over the hills when I changed gear from 3rd to 4th (full boost - ambient temp >25). Until now I have never saw more than one or two green lights. Should I worry?
JIM

mrkimpreza

Note that there is knock correction but there is no (digital) knock signal !!!

I assume the ECU has seen knock before at similar conditions and stored the countermeasure, i.e. knock correction.

AFAIK there is NO KNOCK AT ALL based upon the digital (0/1) knock signal.

Or am I completely wrong....


Mark.

dowser

Reset ECU and find out...carefully!

Richard