When cold, for the first five minutes of a journey and at idle - So basicaly when cold my MY94 WRX runs very eracticaly.

Would this be the idle sensor. If so what is the best way to clean it.

If feels more like the ECU trying to find its feet and buggering about with the amount of fuel it feeds to the engine.

Would it be anything to do with the coil packs?

I am not a real techy person. But any advice on what it could be would be appreciated

Best wishes
Steve

 

Sounds a bit more like either oxygen sensor or maf to me, as these can play up either hot or cold

 

mine my99/00 when cold drops to 400rpm before bouncing back up at lights/rbouts.as soon as warm no prob.
be carefull i broke idle sensor trying to move it in and out and bang went 364.00.no fault codes present either.
what exactly does urs do

 

Didn't think the ECU uses the signal from the oxygen sensor at cold because it doesn't work until heated up. That's why it's got a heating element in it, after a few minutes it will be working but if the problem is immediate from startup I'd suspect something else.

Just IMO.