Doza

Hi I have a 997 c2s 89000 miles my cel light has started coming on in the morning i.e. Cold engine start
When 1st starting its fine for a minute or so then revs drop and runs rough and cel light comes on then revs pick up runs smooth and cel goes out then drops again in this cycle for about 10 mins until warm then is fine again until cold start code reader says p0300/p0301/p0302/p0303 misfire I have replaced plugs and coil packs oil filter oil etc any ideas please

Devil Boy

I just Google searched P0301-3 and found this. Since you already replaced coils and plugs, personally I'd troubleshoot the AOS next. A failing AOS could be a possible source of vacuum leak and cause misfires. Do you notice any smoke on start up? A bad AOS will allow oil vapor into the air stream and foul your plugs and blow smoke out your exhaust. Did your plugs seem wet when you replaced them?

MAF could be a candidate too but I haven't had a MAF fail on me yet, only the AOS.

•Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
•Incorrect ignition timing
•Vacuum leak(s)
•Low or weak fuel pressure
•Improperly functioning EGR system
•Defective Mass Air Flow Sensor
•Defective Crankshaft and/or Camshaft Sensor
•Defective Throttle Position Sensor
•Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems

Doza

Thanks for reply yes it does puff a bit of smoke on start up , do you know is the aos easy swap what's involved thanks

DC911S

AOS not an easy thing to get at. I think there are threads in here on its removal and replacement.

Devil Boy

Yeah, AOS is a pain in the *** but is a DIY if you're capable.

Doza

Started it tonight no smoke and no cel ticks over at 800 rpm take oil cap of and revs raise put cap back on revs drop close to stall then picks back up ran it for 10 mins no cel looks like I'm going to have to bite the bullet and take it to an Indy