CEL on and rough running
 

Totally out of the blue today, my 2003 blob WRX started running rough, like a misfire, and the CEL started to flash. The light then went away but it still ran rough. This happen twice, and now the light is on permanently. I've run a code reader thru it and it's come back with P0303 and P0302 which is a misfire on cylinder and 3 and also P0340 which is something like crank position sensor fault.

Has anyone else had something similar? Are these problems related at all or is it likely that the cylinder 3 coil pack is fubar and having a hissy fit with the other codes?

I've had a search but found nothing quite like this.

Any help will be very much appreciated :)

p0303 is mis fire cylinder 3, p0302 is misfire cylinder 2. P0340 is camshaft position sensor

all these faults at once, I would put money on a the neutral position switch as it can throw up these fault codes, though I'm not sure that would cause the rough running?

Is that a big (expensive) fix? If it is misfiring, that would be the roughness wouldn't it?

its about £40 for the switch and I believe its quite simple to fit.

The reason I say I'm not sure it would cause the rough running is because I can't remember if it caused actually misfires or just misfire error codes. Worth searching P030 without the final number as the last number refers to the cylinder or search neutral position switch

Ok I will do, thank you very much.

Have you heard also about cylinder 3 coil pack giving up due to the heat from the turbo next to it?

Could I be really that unlucky and have both these items go at the same time?

I know this thread is nearly 4 years old, but it's more of an update for search purposes.

Turns out the reason for the CEL and rough running was that the cambelt had slipped 4 teeth, due to the cambelt tensioner giving up.

I took it to Triton in Bournemouth for a routine cambelt change at 100k and they found the problem then.

Apparently, the belt can slip up to about 7 teeth before any damage occurs. Turns out I was pretty damn lucky.

If it isn't already common knowledge, the tensioner should be replaced at around 100k miles. Mine seemed to give up exactly then :roll:

Hope this helps someone in the future!!

Thanks for the tip. My wagon is on 94,000 so I'll go and check the history!

I realise this problem is now solved, but also thought it might be worth posting what I found when I recently had a P0303 code (on its own).

To check whether the coilpack could be the problem, I swapped the coilpacks between cylinders 1 and 3, and cleared the code. When the code came back, it was still misfire in cylinder 3, so the coilpack wasn't the problem.

I then put some new spark plugs in, and it was all good. Checking the coilpacks first was worth it so I didn't replace them too!

Old vs new plug (big gap on the old one!)https://cimg2.ibsrv.net/gimg/www.sco...bb240f5b1a.jpg

Late last week my Forester EJ20 N/A suffered the CEL illuminating, the vehicle running rough and in 40 miles (to get home) used loads of fuel.

I have had the cam belt and idlers replaced at the main agent about 2000 miles ago and it was booked in again as a ''belt'' was squealing on start up.

Having read Davalar's update I wonder if the main agent has not tensioned up the cam belt correctly!

I also hope I have not damaged the engine!!

Richie

Good luck.