Acemotel

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Hi I have a 98 Impreza turbo, 2 years ago the engine blew up and was replaced with a Legacy lump.
Everything was fine until recently....

From cold the engine starts and idles perfectly, after 5 minutes idling it coughs, pinks a little, smells of fuel and dies.
It will not restart unless left for an hour or so to cool down.

Once re-started if you raise the revs to anything above idle it will run and run no problem, if a little smokey - almost like over fuelling.

Items replaced -
All coil packs
Ignitor
Crank sensor
cam sensor
MAF
ECU
Temp transmitter

Tests (which all appeared to be within tollerances)-
Fuel pressure
Compression
O2 sensor
Wiring to and from ECU

Im wondering wether it might be something to do with the induction side of things -wastegate control solenoid etc etc.
Any advice would be most greatfully received as its getting a little boring now

banny sti

iTrader: (68)

Engine management issue possibly.
Although already replaced.

David_Harden

For me, no question, it's your O2 sensor. I had lots of poor running problems and spent ages (18 months!) looking for problems but to no avail. There were no check codes.

Finally I was advised to replace the O2 sensor, and it ran beautifully. These things tend to have a finite life. I've changed 2 now. Even if you've not got a check code and if you've checked the resistance and it looked okay, like I did, yes, change the O2 sensor!

Only about 65 quid from www.lambdasensor.com

David

Acemotel

Thanks Dave Ive got one winging its way to me now.
Regards.

Acemotel.

Installed O2 sensor and still the same
Any other suggestions?
Cheers

David_Harden

Oh man. I was sure if that. Sorry it didn't fix the problem. I take it you got the right sensor for it? Was yours a 3 wire? One black and two white. Zirconia sensor, 0.1 to 0.9 volts (11984 model on the website). Can't remember the Bosch part number off hand.

So, you've already changed the engine coolant temperature sensor? The one thats on the block near the turbo and intercooler?

David

Acemotel

Hi Dave, ye the sensor was the correct one.
Ive since found the problem
The CAT becomes partially blocked once it warms up, this affects the O2 sensor readings, due to the extreme heat, and of course exhaust gasses start popping back through the inlet.

I think the O2 sensor readings go through the roof thus telling the ECU to pour in too much fuel. So 2 odd problems for the price of one.

What a relief
Many thanks for the help.
Alistair.