OcTag3n

iTrader: (4)

Hi all,

I just fitted a new AFR gauge & a new Lambda sensor. the gauge seemed to be working ok for the first week, showing optimum/rich at full boost. However, over the last couple of days as the boost comes in & hits 1bar, the AFR gauge drops down through optimum & into lean & then off the lean scale completely.

Any ideas as to what is going on? The knocklink only flashes one green.

Thanks for any help.

lightwave693

check your fuel pump and fuel pressure.

on idle and off boost does the gauge jump around from rich to lean? thats what it should do, kind of shows the lambda is giving full voltage range, if its dropping to lean on full boost id drive off boost untill you find the problem. check your fuel pressure, pump might be fooked.

Rich

OcTag3n

iTrader: (4)

I just checked the ECU for error codes & it threw up code 23 (MAF)

Thanks for your help mate but it looks like the MAF is the culprit.

rigga

iTrader: (4)

Thats one of the reasons i installed a afr gauge on my my00 as they have not very robust maf's.... when they fail they run the engine weak, so the gauge, although not extremely accurate as its a narrow band item,will give fair warning to problems..... a lucky escape,could have proved expensive without

OcTag3n

iTrader: (4)

Very true. Some people laugh at these safety measures but the cost of them more than out weighs the cost of a new engine. Glad I bought the gauge, & just in time too.

OcTag3n

iTrader: (4)

Right, new MAF in & still the same trouble with the gauge.

Changed the fuel pump back to the original pump as I recently fitted a new walbro but the gauge still shoots down to lean as the boost comes up to 1 bar.

Could it be a faulty lambda or a faulty gauge maybe?

What else could I try? The detalarm only flashes 2 greens when giving it some beans which makes me think something is wrong with the gauge. Wouldn't the detalarm show more activity if I was running lean?

Any help greatly appreciated.

rigga

iTrader: (4)

poor earth on the gauge wiring? ive read they are very sensitive to having a decent earth,although a faulty lambda could well be the source,the maff code has gone now i take it with the new one fitted?no lambda codes come up as well?..... could take it for a mixture check at a rolling road to see if it is actually running weak or not.

OcTag3n

iTrader: (4)

I will check the earth on the gauge. I'll also check the O2 senser. Yes the MAF code has gone now & after I reset the ECU the car is performing well, just this doubt remains about the lean running still. No other codes are stored in the ECU.

Thanks for your help rigga, much appreciated

silent running

Well by what you've said yourself, it's been working fine and it still reads perfectly well most of the time, just that when you cane it, it goes gradually more lean. Hmmm...there's two explanations, bearing in mind that an AFR gauge is a very simple device that basically turns a voltage output of 0-1v direct from your lambda sensor into a display:
1. You have a weird fault with your gauge or wiring, that strangely only happens when you're at full boost and flooring it and then goes back to working fine the rest of the time.
2. Your engine is running lean at full boost.

I don't subscribe to this nonsense about 'narrow band' AFR gauges being inaccurate or somehow inferior to a 'wide band'. Standard AFR gauges for in-car use are for the most part totally accurate unless you've got a really shoddily built one, and they do exactly what you want them to do i.e. show if your mixture is drifting off too lean on full throttle. If anything a standard 'narrow band' gauge is BETTER because it's bloody obvious that you've gone off the scale!

Trust what your gauge is telling you. That's what you installed it for, surely? Have the mix checked over properly. As for the knocklink, it's not quite telling you the same thing, so lean running doesn't necessarily correspond to knock, although I've a feeling if you just kept your foot down when it went off the AFR scale, you'd soon enough see the knocklink light up like a Christmas tree. Not that I'm recommending you do that...

OcTag3n

iTrader: (4)

Thanks very much for your input.

I have another query. After installing the Walbro pump, could it be possible that it has overpowered the pressure regulator, allowing fuel back to the tank before it gets to the injectors?

OcTag3n

iTrader: (4)

Ok, I've just tested the voltage from the O2 sensor. The voltage drops on the multimeter the same as the gauge, so the gauge is reading the signal from the O2 sensor correct at least.

OcTag3n

iTrader: (4)

Problem solved.

The new O2 sensor had failed after only a week. After fitting a genuine Subaru sensor, the gauge is now reading as sweet as a nut. I paid £30 for a cheap universal 3 wire sensor, the Subaru sensor cost £138!!!

Moral of the story..... you pay for what you get I guess