leetuck

Hi Guys,

I took my car to my local Subaru dealer and they did a 60k mile service on it. Everything was running fine for about 2 weeks then all of a sudden the "engine warning" light popped on for about 30 seconds, then went off. Anyway i left it and the next day the same happened again twice. it comes on for a max of 30 seconds then goes off. I took it to subaru and they said that the light was due to the engine detecting knock. I always put Tesco 99RON fuel in and never change the fuel I use. The guy at the garage said that it could be a faulty sensor and would change it if the engine kept detectin knock.

Anyway, I reset the ecu and everything was ok for a few days then the light comes back on. It usually comes on when im rumbling along at about 2000 revs. The engine can be warm or cold, it doesnt matter. The light just seems to come on randomly.

Do you guys think that it could be a faulty sensor? All i know is that before it went in for a service knock was never detected and i'd had the car for a good 10,000 miles.

One of the joins on my exhaust was leaking the other week (keep catching it on my driveway) and i thought that this may be attributing towards the knock but after getting the exhause refitted and resetting the ecu, the knock is still there!

Oh yeh, I have a MY00 Impreza turbo 2000 (approx 62,000 miles)
Thanks for any help.

Lee

Jolly Green Monster

iTrader: (4)

do you get any flutuation on idle speed.. does it run normal on idle after ecu reset? thinking possible maf failure as common on 99/00..

it would be ideal to establish if it is REAL knock or not.. get it listened to by a speciallist rather than a dealer etc..

rumbling long at 2000rpm in 5th and applying enough throttle to be accelerating slightly?

Simon

rbaz

iTrader: (1)

I think the cel comes on because it gets a bad signal from the sensor not because it detects knock.
If it detects knock the timing is adjusted accordingly.
I would replace the sensor I had one go on mine.

Jolly Green Monster

iTrader: (4)

if it detects lots of knock it can also record a knock sensor fault..

yes it should use less of the ignition advance map but if it is still detting due to the advance map not allowing enough timing to be removed due to it being lean due for example because of a faulty fuel pump or maf sensor it could record a knock sensor fault code yet the sensor is fine.

Simon

leetuck

hi guys,

Thanks for the replies.

The car idles fine before and after i do an ecu reset.

The times i've noticed the light come on mostly is when im at a constant speed in either 3rd or 4th at about 2000 rpm.

I did and ecu reset yesterday morning,drove the car for 10 mins and all seems fine. Left the car standing for half an hour then drove again and the check engine light came on then went off. Not been on since though.

I think I will replace the knock sensor first and see if that helps. Failing that I will go see a specialist.

Many thanks for the replies.

leetuck

Hi guys,

Booked the car in at local dealer for Friday. Said it would be £106+VAT fitted so going to go down that route first..

Thanks

tjmatt

iTrader: (1)

Please let us know the result. My car has been doing this for months, but only ever at very low engine load. I tried a bosch sensor and it didn't like that at all, so back to the old one and still randomly coming on. Still haven't found out whether its running slightly lean or whether the sensor is duff. It certainly doens't ping audibly and Romraider has recorded it changing the timing as a result of sensor activity so it does obviously work.

The only other things is wether some of the exhaust rattles at a certain rpm causing higher vibration etc. I've heard thats a possibility too.

leetuck

Hi Guys,

tjmatt - my prob is like yours. Alway happens under low engine load!

I didnt actually take my car in this morning... I reset the ecu about 3 days ago and the CEL hasnt been on since. I think before the midsection of the exhuast might have been leaking slightly and when i get the car off my drive the exhaust sometimes catches path (my car isnt even lowered either).

I wonder if thats causing the problem... going to wait a few days to see if anything happens.

tjmatt

iTrader: (1)

Light come on in the last few days?

Mine hasn't for a couple of days. Judging by a few misfires at idle mine might be running a little lean at low load.

leetuck

Hiya,
Sorry for the late reply.

No not had the light on at all since the last ECU reset. I made sure that all the bolts on my exhaust were tight and ive been careful when pulling the car off the drive (its easy to catch the exhaust) and everythings been ok so far.

Andy Stevens

Read the fault codes first before replacing sensors on a hunch.

tjmatt

iTrader: (1)

I have read the codes, its always a code 22 knock sensor. I guess ya probably haven't seen my other posts.

Anyway car was worse today held back under load an lit the light so I'm thinking its actually the MAF at fault causing a lean condition. Another reason for suspecting that is the idle has been a little rough and I saw it drop to 600rpm after dipping the clutch.

Its rather annoying its so inconsistent.