ktomass

Thanks Judge for your reply!

Was your sensor knackered?

I'm not too sure what to do with mine; Would the car run any different with new o2 sensor? If not what's the point of changing it!?

I read somwhere on here that it measures AFR and it thus give the ECU info about how much fuel there shoud go in to the engine. But i also read that on WOT the ECU is using just MAF sensor to adjust fueling;

Still very confused about this. The car still doesn't work as it should; i'm getting slight judder in 4th and 5th gear when accelerating on highway; And it is overfuelling massively. Would changing O2 sensor made any difference?

Regards,

Kristijan

Edited to say that whichever other sensor I disconnect i get CEL immediately. And If the ECU is not getting any info from O2 sensor it should give CEL!!!????...or not

[Edited by ktomass - 10/9/2003 9:23:06 AM]

ktomass

Ouch! That hurts! MBC is going out first thing in the morning!

We tried another MAF sensor but it made no difference; what else could be MAF related?

Sorry,the car is Legacy gt Turbo Estate MY92 EUspec.

Would anyone know what is MAF part no. for this car? Is it the same in NA engines and turbo ones? In service we checked the numbers and it seems that they are the same.


Thanks,

Kristijan

[Edited by ktomass - 10/9/2003 11:14:26 PM]

ktomass

Should CEL be on when the sensor is not pluged in? If i disconnect any other sensor I get CEL immediately. Yesterday I got fault code 32 (O2 sensor) from ECU.


Anyone knows what should be done?

K.

The_Judge

I had exactly the same problem a couple of weeks ago. I fitted an AFR, and was getting very lazy lights on the display, so thinking I'd connected to the wrong wire on the ECU, I unplugged the connector in the engine bay to see if it made any difference to the display. It didn't, so I guessed the sensor was knackered. However, I drove the couple of miles to get the new sensor with it still unplugged, and as you say Ktomass, got no CEL. Might it be because of residual voltage...? Other than that, haven't got a clue really!

Ade.

Fuel Crusher

The car doesn't use the O2 sensor all the time, something to do with running open/closed loop, dunno which is which fraid. If you unplug the O2 sensor the car just runs all the time in the appropriate mode. I used to run my car with the sensor (which was new) unplugged as on short journeys it elimitated the hesitation when cold, again something to do with the whole open/closed loop thing, never got a CEL. Plugged back in now as I've found NF race practicaly cures the hesitation as well.
I'm sure a more knowledgeable person will explain all this in more detail, if not do searches on open, closed loop etc for some possibly useful info.
Regards
FC

The_Judge

Sorry for delay in reply, just had ADSL... which is nice!

I don't think it was totally shagged. The car's done 36K miles, and I don't know if it was the original sensor or not. For the sake of £25, I thought I might as well replace it. Soon after fitting, went for a drive, and within a couple of minutes, the AFR was "doing its disco thang", so money well spent.

I think mine did, but more than likely one of those psychological things; "new sensor, AFR gauge working, car runs better". You know what I mean.

In my case, not a lot of point in spending £50 on an AFR meter if the display ain't telling me anything!

Quite right, in closed loop mode, the ECU measures the amount of oxygen in the exhaust gas, and alters the amount of fuel to inject to keep the mixture as close as possible to stoich. The display on my AFR gauge (Autometer) updates rapidly, flicking back and forth around the stoich area, sometimes into lean, sometimes into rich.

Yup, but the AFR gives a good indication as to whether the MAF's working properly or not. If the display isn't rich during WOT, then there's something wrong.

I wouldn't have thought it would, as car is in open loop mode, and not adjusting fuel according to o2 readings. Is your MAF OK...?

I'm out of ideas mate, sorry! I suppose you could always up your boost on your MBC to match the extra fuel...

Regards,

Ade.

ktomass

Thanks M8 for your answers!

We checked the MAF sensor and all outputs are correct, also we tried one from another working car and it was the same thing.

Would anyone know if MAF is the same in NA engines (2,0; 2,2)and turbo ones? In service we checked the numbers and it seems that they are the same.

Hmm, thats a thought, up the boost.... would this help!?

Before I got MBC the car was sometimes running on normal boost (1 bar), but mostly on 0,5bar. It seemed as the ECU was retarding ignition and lowering boost. Don't know why!? And still with MBC sometimes it doesn't work as it should. The car is always running on min RON98.

Now with boost set at 1bar it's literally draining fuel through exhaust!

Thanks for your help!

Kristijan

Bob Rawle

Sounds as though you have a problem .. first off what car are you talking about.

For the ecu to pull timing and drop boost it is seeing DET, it would also drop onto the richer alt've fuel strategy to protect the engine.

You fitted an MBC ... that means you are over riding the ecu reaction and forcing boost, ecu is chucking fuel in to try and stop a problem but you have over ridden.

So its rich, you drown the lambda sensor and get a cel as its so rich its on the bump stop wrt to negative fuel correction.

Suggest you stop using the MBC, let the ecu protect the engine and establish what the real problem is ... most likely maf related.

cheers

bob

ktomass

I changed MAF (part no. 22680 AA160; is it correct one?) today and guess what; it made no difference!!

I'm completely out of ideas.

In 4th and 5th gear car just doesn't pull, i get slight judder and massive amounts of fuel are going through the engine. Without MBC it is boosting up to 0,5bar. Sometimes it happens; usually when driving with 2/3 of a throttle at 180 kph, when suddenly the car starts to fly, and it's working for some distance, soetimes even for a day or two, boosting max to 1bar and then goes back to "normal mode".

Any advice will be greatly appreciated!

Thanks,

Kristijan

greasemonkey

Probably more to do with the AFR meter fooling the ECU into thinking the lambda sensor is still connected.

Bob Rawle

These ecu's have a bias on the lanmbda sensor input so that when its disconnected it reads about stoich, hence no cel "usually" although it can happen.

The ecu is dropping into limp home, if maf made no difference then it could be you have a faulty knock sensor, worth trying another.

bob

ktomass

Many thanks for your replies!

Ok, the lambda issue is out then. Knock sensor...hmm, will try to do something in the morning.

I was just thinking, is it possible that it could be something conected with fuel pressure?

What should be the fuel pressure for this car?

Kristijan

ktomass

New knock sensor went in and no difference Car works the same as before.

I belive we now covered electronical part. We checked knock, maf, camshaft, crank, O2, TPS and sparkplug leads; and everything is ok on this part.

Also we changed sparkplugs, oils (gearbox, engine, diff), filters etc.

What now?? As posted earlier is it possible that something is not completely ok with fuel supply, although it is overfuelling!?

Not smart enough for this car

Kristijan

ktomass

I'm going to check fuel pressure. I read on here that it should be somwhere between 2,8 and 3,2bar on hot idle with vacuum hose of and blanked.

Are this no.OK?

Kristijan

ktomass

btt

ktomass

Ok, fuel pressure checked; with vacuum I get 2,5bar on idle and 3,5bar on full throttle. I belive that should be good enough...

Now what else can we do??

Anyone has an idea?

Kristijan

PaulRandy93WRX

iTrader: (1)

Has the car been chipped??? I had this problem with my WRX when i imported it it had some jap chip in it that was advancing the timing too much, the engine would detect a slight knock and retard the timing right back and cut the boost. Worth a check to open the ECU up.

ktomass

I forgot to add, ECU is standard.

Thanks for your reply!

Kristijan

buzzard

check

buzzard

hi ktomass,
you dont say how your engine sounds, ie. at idle is there any hint of knocking? or when you are just about to pull away can you hear any knocking particularly at low revs, as this is when the load will be greatest on the crank.
i ask these questions, as the higher the gear you are driving in, the greater the crank load will be. if there is some wear in the crank/bearings, the knocking produced can be picked up by the knock detector and the ecu will interpret the knock(incorrectly) as the onset of detonation and retard ignition and reduce boost to 0.5bar to help protect the engine. 4th and 5th transmit the greatest load to the engine so any "knocking" is more likely to be detected in these gears.
Have a good listen to your engine.
Hope this helps.
BUZZ

ktomass

Thanks!

Checked it today, no sound whatsoever except from noisy tappets but that also dissapeared when tha car has warmed up.

At idle the car runs very smooth, without knocking or juddering. It idles rock solid at 900rpm.

Kristijan

[Edited by ktomass - 10/15/2003 2:20:20 PM]

ride5000

have you reset the ECU by disconnecting power at the battery for a while?

ken

pch

Kristijan:

Have you tried posting on the Legacy B4 forum, http://autos.groups.yahoo.com/group/legacyb4/messages, there are some very knowledgeable Legacy types there with posts from all round the world.
Boost problems on my MY93 Legacy GT twin turbo, with regular CEL, limp mode, & E66 codes were sorted when I changed the exhaust & cat. Must admit though that no-one diagnoded problem till exhaust fell apart & it had to be changed, otherwise I may well have been still pulling my hair out.


Good Luck......Paul!!

ktomass

I have also reset the ECU by disconnecting the battery and it worked for a while (5km), then the same thing again.

LegacyB4 forum...not a bad idea! Thanks!


Kristijan

[Edited by ktomass - 10/16/2003 5:54:41 PM]

ktomass

Nothing solved yet, but we should be near... i guess

Tody we checked lamda sensor again with voltmeter and we haven't got response from sensor, numbers haven't blinked at all.

That should be O2 sensor not functioning. We checked on my friends car (same legacy but saloon)and on his car ideling we got numbers jumping from 0 to 0,8V (I belive this should be OK).

Now question; is it possible that faulty O2 sensor is causing hesitation and slight judder under acceleration? Still no CEL though! With ECU reset no fault codes. When doing ECU reset via disconnected battery the car is perfect for 5km then the same story.

Kristijan

[Edited by ktomass - 10/27/2003 7:24:12 PM]

ktomass

btt

ktomass

Problem solved with new universal O2 sensor!!

Kristijan