Dark Blue Mark

Hi all,

Got my O2 / Lambda changed under warranty as the idle speed was very erratic, but its made no change. Car still trys to cut every now and then. Any ideas?

The select monitor showed the O2 as being dodgy.

MB MY99

ozzy

MAF??

mutant_matt

I thought MAF too....

Dark Blue Mark

Suppose thats the other end of the control loop, so quite possible.

It didn't show up on the Select Monitor though, so now confused. Its going back either way!

MB

mrkimpreza

Under closed loop control (so during idle) the o2 sensor is always dodgy and going up/down like grazy (at least at my car and on the DeltaDash logs I've seen on other cars).

Look at the MAF I'd say.

Mark.

Dark Blue Mark

I think the o2 reading should bounce up and down at idle, on the monitor, but the revs should hardly move at all. I watched the o2 on the select monitor and it wasn't moving, which the Subaru tech said was wrong. He said the fact it wasn't moving meant it was faulty.

MB

ozzy

MB,

You're right. When John Banks and myself monitored our cars, the revs went quite high (1500rpm) until the coolant temperature started to rise (obviously warming things up). It then began to work it's way slowly down over a few minutes until it settle around the 750-800rpm mark. John reckons the MOT range is between 750 and 1050rpm for idle.

The O2 sensor should rise up and down in a smooth wave although the wavelength is quite close (so don't expect a nice Sin wave to appear).

Mine is suspected faulty (although, the Dealer found no fault on the Select Monitor). Deltadash clearly shows the sensor only reading between 320mv and 325mv so God knows how they missed that.

Maybe the replacement's faulty too. Did they check it again on the Select Monitor ??

Was your idle dodgy all the time?? Mine only seems to be bad after I've drive above 4000rpm. If I potter along off-boost, the car's fine. I've also noticed by fuel consumption fall quite badly. Have you noticed that on your car??

Stefan

[Edited by ozzy - 5/14/2002 10:56:30 AM]

EvoRSX

Dark Blue,
Do you have a vent to atmosphere dump valve fitted?

Andy

Dark Blue Mark

Stefan,

Yep, it doesn't always do it and usuallt when you come to a quick stop. The other time is if sat in traffic and you blip the throttle, the revs sometimes drop and cut, or bounce righ back up again.

Andy,

Good question. I had one once on a previous car and it gave the above symptoms, took it off and it was fine again. I suspect that's an air leakage prob? This car has a standard one, no leaks.

MB

mparsonage

Mark,

You can borrow my AFR meter if you want to monitor what the Lamba sensor is up to. Or, better still, borrow my multi-meter to monitor the whole voltage range - AFR is set to only monitor 740mV to 940mV.

ozzy

Mparsonage,

Do you know how to monitor the 02 and MAF sensors using a multimeter on a MY99??

I'd like to double-check them both as more evidence for the dealer.

Stefan

ozzy

After a quick search on Google, I stumbled across this. Anyone know if this will work OK on a UK MY99???

How-to check MAF

Stefan

Dark Blue Mark

Thanks Mark,

Its going back in on Monday 27th so might give you a shout between now and then. Where does the AFR plug in and what make is it? I had an Apexi one which I never fitted.

MB

ozzy

If, you go back a level on that site, there's more info.

http://www.geocities.com/kuleshoff/subaru.htm

Stefan

Adam M

the O2 output should always oscillate in steady state.

the ecu does this on purpose as controlled periods of running lean and rich average out at stoich but also systematically purge the catalyst and NOx trap alternately.

ozzy

As far as the MAF goes, it looks like the US guys have tracked down just the sensor on it's own and not the £300 assembly.

http://www.scoobymods.com/forums/sho...id=887#post887

Anyone care to ask their Dealer if it's the same over here in Blighty ??

Stefan

mparsonage

You can monitor the lamba sensor by tapping into the wire that comes out of it and goes to the ECU. I did this at the ECU end of it - you don't need to cut it if it's only a temporary installation. The pin to connect to is detailed in the Link manual (page 33, connector B136, pin 21). The 5th post on this page shows how the voltages correspond to %CO.

Looking at the manual, I guess you could also do the same to monitor the Mass Air Flow sensor but I've not tried this. That site you suggest Ozzy seems to use a similar idea. Don't know whether this will work on an MY99.

Mark,

It's the one that a few people on here made a couple of months back - mainly designed by John Banks. http://www.scoobynet.co.uk/bbs/threa...D=57428&Page=1

ozzy

MParsonage,

That looks great.

Many Thanks,
Stefan

john banks

Only caution with using a multimeter to read ECU sensors - particularly the lambda sensor is to only use something with input impedance above 1 and preferably 10 megaohms. So this rules out analog but includes most digital multimeters. Otherwise you fry the lambda sensor by drawing too much current.

You can also tap MAF, TPS and MAP - I have not done any others, but you could also tap some of the frequency signals like RPM and vehicle speed if you have a frequency function on you DVM and know the calibration. You can also read the wastegate duty cycle if you feel like it and you DVM will do it. The link manual as posted above again helps a lot.

[Edited by john banks - 5/14/2002 5:30:04 PM]

GavinP

Regarding the replacement MAF sensor element - if you can't get them in the UK, you can order from here:

http://www.subaruparts.com/cart/?pn=...=13&submit.y=4

Works out at £45 inc shipping (excluding customs duty if applicable)

Thanks

Gavin

ozzy

Now, why can't we have something like that over here. Seems the brits just change the dollar symbol for a pound one when making-up prices

Stefan

WREXY

The part number on my MAF replacement is 22794AA010 for a MY99/00. This is the MAF without the housing.

Cheers,

Wrexy.

Dark Blue Mark

Seems to have sorted itself out now??

MB

[Edited by Dark Blue Mark - 5/19/2002 1:12:05 PM]