Swapped my PPP ECU into Ozzy's RB5 the other night and it is going great except one issue - idle speed. We are going to datalog it on DeltaDash tomorrow night. His car after a blast seems to fluctuate the idle speed between 800 and 1000 now and again, and then drop to pretty low, but it is intermittent. Never did this on my car, and his ECU did not previously do it on his car. The only other points:

1. I did not reset the ECU before putting it in Ozzy's car
2. He previously had a CEL for lambda sensor after fitting a cat back exhaust but this cleared itself
3. He has an ITG filter

His car is otherwise standard and petrol consumption is not excessive and there are no hesitations.

I will be carefully looking at the lambda and MAF sensors in particular.

Any other thoughts? I was going to try a proper DeltaDash ECU reset after looking for present or historical codes, failing that try adjusting the idle speed in DeltaDash to stabilise it. If not swap the ECUs back and see that it still works OK on my car and the AE801 still works OK on Ozzy's.

 

Sounds like your plan is spot on John. Can't think of anything else to try for now....

Matt

 

My car (p1) showed an historical MAF error code, not current.

However, it showed similar symptoms to you and was especially bad when cold, although I didn't realise how bad it was til it was replaced.

Wouldn't a reset be the best place to start subject to the error codes ?

 

Think so. Lambda sensor can do exactly this too from what I have read, and he previously threw a code for this. Otherwise a vacuum leak, or even the throttle position sensor. Coolant temp, MAP sensor too - all can do this. Will check it all out.

[Edited by john banks - 4/22/2002 11:30:02 PM]

 

Sounds like a duff MAF. Swap one off another car for ten minutes and see.

Four bolts, one screw and one connector.

Steve

 

It was the lambda sensor - continuous 320-325mV with the odd weird spike when driving at open loop - never went above about 350mV and no dodgy connections. There was no airflow correction at idle. Thankfully there wasn't much knock correction either, just a big waste of petrol and an MOT failure with rubbish idle.

Delta Dash is GREAT!

 

I'll second that, Deltadash is awesome.

You could see the problem right there on screen - a very sick looking 02 sensor.

If you're a true enthusiast like John, the software is a must.

Stefan

 

It shouldn't.

BTW, why are messing around with the Scoob when you have a fully functioning Time Machine

Matt

 

That is a Scoobynet bug I believe?

 

Has been known for lambda sensors to be failing under certain circumstances rather than failed units.
My own car which is nearly 3 years old has had 2 replaced under warranty. Car ran well enough but as John has said, it's a great thing having the facility to see the sensor misbehaving. Without it, you are none the wiser.
My friendly dealer accepted my word on the sensor failing and replaced with no issues.

 

not a feature
is a bug

if it was software.. and it came into our company... and we said 'we cant reproduce it just now so its not a problem' then we would lose business and customers.

same old same old

if only money was unlimited....

 

I'm not a gambling man but, I would put my money on intermittent (sp) MAF.

Best o' luck, MD.

 

Yeah, that thought has crossed our minds too.

The trouble is, Deltadash clearly showed a problem with the O2 sensor readings. The MAF readings looked spot on.

Rough idling's a common sympton of a duff MAF, but so too for a duff O2 sensor.

I can easily demonstrate the problem by giving it some stick through some twisties. Hopefully, if I can show the Dealer the problem, they'll agree to change either the Lamda, MAF or both to see which one fixes it.

Stefan

 

The lambda sensor was reading between 320 and 325 mV on our previous log no matter what we did apart from the occasional spike. Has to be faulty.

 

John,

Do you know if the Subaru Select Monitor shows this type of info (i.e. live data from the ECU)??

Stefan

 

Yes it does, just a bit slower. It can record data too, for later viewing, though _I_ can't work out how.

The best view to choose is the 4 channel data & graph view. You can then view engine speed, lambda and air flow on the same screen.

Cheers

Steve

 

Thanks Stephen.

So, God only knows how they couldn't spot the fault. Even on idle (and without the usual hunting going on) the Lamda sensor only ever went from 320mv to 325mv.

It's not like they had to actually go and drive the thing to see it happen

I'm playing football over lunch, so it'll probably be tomorrow before I can speak to the Dealer.

Stefan

 

Constant 3/400mV = working lambda sensor ??? Hmmmm...

Please let us know who the dealer is, so we can avoid them like the plague !

Steve

 

My car's almost out of warranty, but to be fair to the Dealer, they have happily fixed a lot of faults under warranty in the past few weeks.

It's only been small things like rusty PIAA spots, lettering/stickers falling off bodywork, scratched front windows, etc., but I think they'll drag their heels until the cars out of warranty for any sensor faults.

Maybe it's just IM, that makes them like this

Anyway, on the positive side there's a new Dealer opened closer to me, so maybe they'll be keener to help.

I'll keep you all posted.

Stefan

 

Well, it's been to the Dealer and I was told "sorry sir, but we couldn't find a fault".

I contacted the new Dealer (Drive) in Falkirk, but they're still in the process of getting the Select Monitor setup by Subaru

Looks like I'll need to take the afternoon off and pay Eaglesham garage a visit

Other than pi$$ing petrol down the dain are there any bad effects from have a dodgy O2 sensor? Is it likely to run too rich or too lean? I've noticed the backbox is really sooty (and no not the glove puppet)

Stefan

[Edited by ozzy - 5/14/2002 7:06:57 PM]

 

If it is running really rich, it won't do your cat much good.

Steve

 

Does having a sooty exhaust mean I'm running rich or lean?

Only the cat in the downpipe left and that's soon to be removed anyway

It's not going to fry any internals is it?

Stefan

 

Sooty is rich.

Making your exhaust less restrictive should lower your EGTs and this is a good thing.

Steve

 

Thanks Steve.

Might take tomorrow afternoon off and get it sorted once and for all.

Stefan

 

What is the relationship between the MAF and the O2 sensor??

Is it possible for the MAF to be faulty and cause incorrect readings from the O2 sensor??

Stefan

 

You need to go to a tuner with an exhaust gas analyser to be sure. ( Power Engineering has one, errr, two now actually )

Steve

 

Thans Steve,

Unfortuantely PE are a bit far out of the way for that. Since the car's still under warranty, I'll just need to convince the Dealer to try swapping the 02 sensor (and MAF) to see which cures the fault.

Just want to try and understand how these things work.

Cheers,
Stefan

 

First step Ozzy I reckon is to replace the lambda. If that doesn't sort it take it from there, but even if you have to shell out yourself for it you might be able to claim it back off Subaru as you mentioned before?

 

Yeah, that sounds like a possibility John.

How did you get on with your exam? Hope all that tinkering didn't put you off, although a man of your intelligence is bound to have ace'd it

AlanG has kindly offered to let me try his O2 sensors on the way to Eaglesham, so will keep everyone posted on the outcome.

Stefan

 

Update: The car's going in for some warranty work, so I wanted to remove the STI exhaust and ITG filter so they could check out the O2 sensor.

On the way to the dealer, I stopped off for some petrol. A couple of minutes later, the CEL comes on again. So, I pull over and check the diag - 32 Oxygen Sensor.

Now, the strange thing is, the idling problem seems to have disappeared. Any ideas why changing the std backbox on a MY99 Impreza (for an STI one off a P1) would cause problems with the Lamda sensor???


[Edited by ozzy - 5/8/2002 3:17:05 PM]