99 wrx hesitates/surges when cold
 

Hi guys,

I've had my rex now for about a year and ice noticed is getting progressively worse to drive when cold. The CEL (knock sensor code) comes on upon startup and stays on until the car is about a quarter up the temp guage. The light also comes on intermittently when at operating temp.

When it's cold and accelerating, it surges back and forth gently. The afm, plugs, leads, air filter are all about 12 months old.

Any ideas? I thought maybe injectors or even the afm is playing up again?

If knock sensor CEL is coming up would it not be the knock sensor?

I didn't think so because the knock sensor fault came up when the afm shat itself.

There's a cheap "genuine jecs" knock sensor on ebay, maybe I'll grab that and try it out

Any other thoughts people?

O2 sensor
AFM

Cheers, will give them a try. ��