marcevs72

iTrader: (5)

got a puzzling problem with my 93 wrx,every now and then the cel lights flashes and goes out.when i check code it brings up 22 which is knock sensor.car has had new knock sensor a week ago and car running sweet so cant work out why its coming on every now and again.
car has cat back system,pipercross induction kit,walbro pump and just replaced the mines ecu with a standard z4 one.car has just had full service and also changed the ecu coolant temp sensor.
any ideas guys????

ukimpreza

iTrader: (9)

did you do a ecu reset when new knock sensor was fitted?

marcevs72

iTrader: (5)

yep the battery was of for hours as was doing loads on the car.

Glowplug

iTrader: (8)

Was the new KS OE or lesser quality? The cheaper items have been known to be a bit hit and miss! Much like the cheap Lambdas.

Also the KS needs torquing down to the correct lbs for it to operate correctly within its parameters. Over tighten it and you could crack it, under tighten and it will effect the sensitivity.
Another cause can be iffy wiring some where in the KS loom.

I would still do a 'proper' reset procedure. If you are not resetting the ECU after the flash and check, then it will remain stored, therefor it will reshow 22 every time you check it. It only takes 5 minutes and also allows the ECU to 'self check' the system.

marcevs72

iTrader: (5)

the knock sensor was from subaru and have worked out that the only time the cel light flashes on is when i stop and the revs drop to 700-750 which is what the car is ticking over at.could the low tickover be the cause???how do you rasie tickover on the car as well????

Glowplug

iTrader: (8)

Turning the top of the idle control valve adjusts the idle speed, and yes you are right in thinking yours is low. About 900rpm is right.

Bare in mind the ICV may not be the issue here. Also consider for example the MAF and/or the Lambda.

The best thing to do is a proper ECU reset and see what happens from there. Watching carefully for the final 'all clear' or 'error' code.

marcevs72

iTrader: (5)

have just set up icv so ticking over at 900rpm.doing reset later and hopefully things might be ok if not will go down the lambda/maf route.

Glowplug

iTrader: (8)

Is it holding strong/steady at 900rpm?

Yeah get that stored code cleared. The lambda and the MAF are testable if they are still suspect afterwards.

marcevs72

iTrader: (5)

its staying spot on at 900rpm.i have a techtom fitted as well so a lot more accurate than the dash.its had white dials fitted as well so dash not that accurate

marcevs72

iTrader: (5)

well looks like its the lambda that is playing up.when car running ok the voltage showing on the techtom for the o2 sensor is 0.26-0.30 v but when cel light comes on it is showing 0.01-0.08 v which is not right.what you all think???

Glowplug

iTrader: (8)

Depends on what your doing. At tick over it should flick between 0.1 ans 0.8. on boost it should show rich, 0.7+.

marcevs72

iTrader: (5)

at tickover its 0.00 to 0.08 and when driving goes up to 0.40-0.50.just cleaned the connector for lambda as one of the contacts was rotten and seems to go better now and showing 0.6-1.0 on boost.going to pop down to alan jefferies on monday and have a natter

Glowplug

iTrader: (8)

Good move.