Fault code P301

[Ben123]

Hello,

I've deleted this fault code on my Forester 2001 non turbo, but after a few short journeys it keeps returning.

'Apparantly' this means misfire on number one cylinder.

It doesn't  seem to misfire, seems to run fine. Though i put in new spark plugs and swapped over the newish HT leads... the code still returns. I pulled off the spark plug cap with the engine running and yes it misfired, so normally it seems to run fine, though i have to admit that it doesn't quite have the same power that it used to, which I suppose is normal for a petrol motor with 160,000 miles.

I'm wondering if other owners have had the same code with the same lack of noticeable misfire?

What is the most likely cause? And am i best to just ignor it?

Is there any problem with constantly driving with the check engine light  illuminated?

Thanks for any helpful replies.

Ben 

[Mr B]

Do a compression check old school with gauge or quick test via relative comp test with a scope, possibly low compression (low contribution from cylinder 1) .

 

[Ben123]

Thanks, good idea.. will do. 

Ben

[Ben123]

Hi, I just returned from the local mechanic who told me that because it seems to be running fine, that a compression test probably wont give a definitive result and therefore is probably a waste of time and money.

He guesses that it is probably an fault with the sensor or an electrical gremlin.

 

In conclusion i'm thinking to ignor it, and just delete the code each time before i go for an MOT. But I would like assurance from someone out there that when the code is active and the engine warning light is illuminated, that the computor settings for engine management are normal.. In other words I want to be sure that the engine isn't running richer than normal or with less power than normal just because the light is illuminated.

 

Finally, how many miles can i expect to get from this engine before it starts to wear out? It already has 160,000 miles and consumes a bit of oil..  and the clutch is on its way out...  Yes i'm trying to avoid spending much money on a car that probably doesn't have much life left in it...

Thanks 

Ben

[Mr B]

It takes less than 10 minutes do a relative compression check and useful as gives idea on engine health in general as well as some direction on your issue.

It indeed likely CPS sensor, coil or wiring related but without some test data on basics you just guessing and have no direction in trouble shooting it .

I see these NA engines at over 200K without much drama, relative comp test give you some useful data to it's condition and life and if shows lower comp on cylinder 1 may show reason for the code .

 

[Ben123]

Good point, thanks, I'll arrange a comp test...