benji100

does anyone know if there is anyway i can tell if my afr meter is working correctly? i've got a 94 wrx running the apexi fc etc with the acvr aswell, in 2 situations now it has not worked after the engine has been started, its a lamda link meter and when u turn on the ignition it initailizes but doesn't do anything after that, then after about 5-10 minutes it will start working but doesn't seem to reading right, as when on full boost it usually hits 11-12 on the meter but now is leaner, about 13-14. i've also had a problem with det, but its not all the time, somebody said it could be a faulty oxygen sensor as this could cause det etc, another sign is sometimes when the car is started it smells of fuel occasionally, does this sound right, please any experts out there got any ideas????? any advice would be good.

silent running

Don't know the specifics of your meter, but if it's taking a signal from your lambda sensor and it's not right, then either your lambda sensor's knackered or your meters is, or the wiring between them is - simple as that. The fact that the meter works under some situations, particularly after 5 or 10 minutes, suggests to me that the lambda sensor is at fault. Lambda output can 'drift' a little as it warms up but it's seconds rather than minutes. IMHO

benji100

thanks very much, is lamda sensor the same as oxygen sensor?

Mo

Benji, get it checked by someone with a wideband, the leaning out would almost certainly cause the det however the narrow band sensor is far from accurate away from stoich.

benji100

many thanks, whats the difference in narrow and wide band?

KenS55STI

narrowband measures afr around 14.7 (stoich) which is the ideal ratio for total combustion of petrol. It is not accurate very far from that ratio.

wideband measures roughly between 8 and 22 so is much more accurate.

lambda links usually work off the signal of the factory narrowband sensor. If the sensor is faulty then the mixture 'normally' goes rich (ie less than 14.7) and it's ok except fuel economy takes a dive and idling gets a bit rough, may explain the petrol smell. If the sensor is knackered it shouldn't really affect the afr on boost. If your car is going lean on boost then it may be the maf sensor.

You need to have a diagnostic check done on the car to see if these sensors are ok or not. Checking the AFR with a wideband will tell you what the actual afr is but not the cause.

Jay m A

iTrader: (2)

You won't see anything on a heathly lambda(oxygen) sensor during the first few minutes since it needs that time to get up to operating temp.

Although the OE sensor isn't great at measuring accurately the AFR on boost, its good as a reference point. If its starting to read leaner than before it may be an indication that something is amiss, although not neccesarily the lambda sensor itself. Note that if the car is detting on boost it isn't due to a faulty lambda sensor, since the ECU is in open loop and doesn't set AFR via the sensor - it does it by referencing a lookup table (the map!)

benji100

thanx guys, the afr meter is a digital lambda link that can be switched between narrow band or wide band, (not sure which!) it runs off the standard lambda and another screened lambda that sits just behind the turbo, it never used to take any time to register after starting, its very intermitant fault, best get it to zen.