Sounds as though your connections to the afr are alright. It is reading a low voltage as you know so earthing etc is important. It may well be a poor Lambda sensor, hope you will tell us whether a replacement one cures the problem. I seem to remember someone saying some time ago that if you dont have a sooty exhaust on a Scooby you should start to worry.

Les

 

What about the connection for the Lambda Link at the ECU? Does it matter HOW it's made? Mine is with a Scotchlok type thingy, and I know they aren't ideal, but was loathe to solder it until I knew I had the right wire. Now, I can't be bothered to get it all undone agin, and anyway, I can't find my soldering iron, (Kids, who'd have 'em??) :
Alcazar

 

Yes the connection is very important when you consider the measured variable(voltage) is relatively small(millivolts) so any resistance may impair the accuracy of the monitor. You know you wanna solder it!


Cheers

 

hmm, think I will solder mine now, Im happy the Earth is solid

 

Worth soldering it I think.

Les

 

sonic i had the same thing as you red led on wot with oe air box in place the problem i had was the maf sensor under reading on wot put a new maf sensor on and bingo blue led on wot, so id say try a new maf sensor. I had that k&n on my car sonic after fitting the new maf sensor and had no change in the afr readings
new maf been on for 1 year dawes set at 1.25 bar and blue led on wot every time

 

Would delta dash tell you if the lambda or MAF were failing?

 

I might go to the dealers on Saturday, and get it on Select Monitor, dont have delta dash or PSi 3 yet

 

Remember when you go that a failing MAF or lambda won't show up on select monitor - that will only 'know' once it has failed (when the CEL would come on anyway!).

 

Hmm, so it could be Lambda Sensor or the MAF !!!

Anyway to tell for certain ?

Ive driven 120 miles this morning, mostly motorway, car seems fine, but AFR was off for 90% of the journey, with the occasional blip of red

 

Think Ive ruled out the Maf Sensor, I started the engine, unplugged the MAF sensor and the engine died almost straight away

Did a chek on black connectors, check engine flashing as normal, tested the voltage with my better bigger multimeter, and on tickover voltage was around .750v held revs about 3k, and voltage went to about .850v then back to .750v for idle

is there any damage that can be caused while driving the car with a faulty Lambda Sensor?

Steve

 

I was led to believe the ECU goes into safe mode if it fails. Might be crap, but it rings a bell...

Is disconnecting the lambda any good as a check for anything?

MB

 

hmm, interesting, what are the consequences of disconnecting the Lambda whilst the engine is ticking over

Like the Maf for a quick test to see if it is ok or not

Steve

 

Also forgot to add

I disconnected my Battery last night for a few hours, to reset the ECU

this morning I was going upto and over 5k rpm and staying rich (first time ever) even upto 6k, where is slowly started to run to the yellow (Stoich) leds

Then after a few more goes, it was back to normal, and afr stopped reading for the rest of the journey, cept when on idle, or in 1st & 2nd gear

What seems to happen, is that once the engine is sufficiently warm, then the afr only registers in very low (sub 2k) revs in 1st & 2nd only

 

My AFR Always runs on the Green on WOT (all gears).
It can be totally off at times, but goes up and down at 1Hz when crusing.

are you sure this is correct???
Surely we should screen the wire all the way up to the AFR guage to prevent interference from other wires under the dashboard??

You can get a few mVolts of pickup without trying in a bundle of wires (electromagnetic interaction).


james.

 

When I had a problem with my car stalling / idle buggered etc, it was the MAF. My AFR was doing all sorts of weird things, so I thoght a wire had come loose.

To check it wasn't the lambda, John B asked me to disconnect it while at idle. Also re-assured me it would be ok to drive it like this for a short while. Symptoms stayed the the same and thus pointed to the MAF. Went to PE and had it replaced, problem solved!

Im confused as to why it wont give a good reading above 4-5k? I would say, as the signal comes directly from the lambda wire, that it may be tired. If it gets worse on a journey, it may be being affected by the heat. Not read the whole post, but I would check the mV reading to the AFR, or the reading direct from the lambda,into the ECU.

Or easier just to get a new one, and take it back if its not the problem. My bets on the Lambda though.

MB

 

Also,

What connector pin no are you using for the signal? I know it sounds dumb, but its bloody easy to use the wrong one! Theres a good diagram on the ravensblade impreza site.

I almost got it wrong as the diagram shows looking into the mouth of the connector, rather than the other way

MB

 

Im using B136 Pin 21 on the Blue Connector, white cable with silver dots

It does get worse when warmed up properly, not too sure how to check from the Lambda end (without burning my hands on the turbo heatshield and knowing which wires to connect the multimeter too

I have an almost perfect idle, and nothing really to indicate that the car is running bad

Couple of things then,

the Purple wire to ECU isnt soldered, its connected using them block connector things that crimp the cable

The Positive is connected to the Cigarette Lighter Power ( I will probably change this to somewhere else)

I havent twisted the wires from the Gauge to the relevant place (would this help at all, and could the stereo cabling affect the signal)

the Earth is now connected to the ECU Bolt, in turn a big Earth Strap goes from there to the Battery Negative Terminal

Would there be any gain in shielding the AFR Wires (they are very thin) but I would have thought that if it were a wiring problem then the higher voltages would register, and not the lower ones

Steve

 

Sonic,

The twist on wires will always help as signals induced should canel each other out (as with CAT 5 cabling).
The cables will be more resilient to interference if they are screened, a mod i will be perorming on mine.

I suggest a Screen at the ECU end which is NOT terminated to GND at the AFR end. This should take any induced signals to ground and protect the signals in the wires going to the AFR.

The live feed shouldn't matter at all, this will just power the circuitry in the AFR meter itself, the earth shouldn'r really matter provided that it is low impedance between the connection and the battery (mine was 0.1Ohms to the battery).

J

 

There was a big debate on earthing a while back, personally I would use the ECU earth as thats what the lambda uses.

MB

 

Note that a screen should only ever be connected at one end of
a cable run to avoid circulating currents in the screen which in turn get induced into the signal wire.

J.

 

Steve, does the display change when you switch your lights on??
To test the voltage with a multimeter you muct connect the earth lead to a good earth and the live lead to the point where you have made the connection for the afr.
I know people have different views, but i have fitted a number of AFR gauges for people and have found that..
It makes a differnce to the display if the Power source is not adequate ie. Cigarette lighter..
The best place IMHO is at the ignition switch.
The earth to the AFR must be connected to the battery also (you are OK on this one).

A number of people have fitted Autometer gauges and had poor/non displays, after removing the live signal from Stereo and cigarette lighter feeds and hard wiring into the ignition switched live (fused) as well as earthing to teh battery the gauges work fine..

And just to confuse things....
I reckon its the Lambda

Check you voltage output from teh Lambda mate

Rob

 

However on 2nd thoughts.... a failing MAF would give the same symptoms :S

Rob

 

Fixed mine anyways....it seems the tape I used as an insulator had started to break down and conduct!!!!

Sonic....Your best bet if you're not sure is to borrow a MAF. They're dead easy to swap about and it will give you a conclusive answer. Just be nice and gentle with it: They are kind of fragile on the newer cars.

FWIW Get rid of the scotch-block. They are complete pieces of ****. Twisting the wires together gives you a lower impedence connection in most cases!!!!

If you're down in london, I'll even solder it for you, if you
want

 

Cheers for the help again

No London trips for me at the moment, Im stuck in Mansfield at the moment, If I get home tonight (ie finish the work im doing here) then I will remove the scotch block, & change the power feed, to see if it makes any difference

I did the disconnecting the MAF thing, and the car cut out, so I assume that the MAF is OK, not sure how to test the Lambda tho, and cant get to my dealers till saturday at the earliest

Once I change the Power & Scotch Block I will retest with the Multimeter again, & a drive and see what happens

Cheers

Steve

 

Dealer won't tell you much, there's far more expertise on here (And Power Engineering ) as I found.

MB

 

Disconnecting the MAF with the engine running doesn't really mean THAT much IIRC.

I think driving with it disconnected makes the ECU go very very rich. Wide open to correction here.

 

Am i right in saying the maf sensor controls fueling on wot.

 

Right, well I have removed the connectors now, and soldered the wires to their relevant places

No different, exactly the same, rich in 2nd upto 6k, then stays rich in 3rd, 4th & 5th upto 4k, then drops all the way to lean, and then off

Im beginning to give up, and almost about to remove the gauge, as ignorance was bliss !!

 

Sonic,


Try using a screened wire for the AFR Voltage.
As suggested, earth at the ECU end, but then ensure screen is not terminated at the AFR guage end.
This is certainly worth a try, I've been working with comms and electronics for 6 years, you wouldn't believe the interference and pick up you can get induced/cancelled out in cables just by running near other wires.

Just touch the AFR purple wire with your fingers for a demonstration (doesn't take much when dealing with mV.

James.