Jump to content
Ultimate Subaru Message Board

Recommended Posts

My wife's 96 Outback threw code P0304 (Cylinder #4 Misfire) last night after sitting at the airport for 2 days. The light went off by itself today. I ran the code when I got home this afternoon. It has also been throwing code P0420 (Catalyst below efficiency) about once every 4 weeks also after sitting for extended periods.

 

Is this anything to be overly concerned about?

 

Thanks,

 

John

Link to comment
Share on other sites

The cylinder misfire code could be as simple as moisture in the gas - if it reoccurs, more diagnosis is required. The catalyst below eff. code could be the oxy sensor after the cat converter (there is 2 on your car - 1 b4 the cat and 1 after). How many miles on the car and have the oxy sensor(s) ever been replaced?

Link to comment
Share on other sites

Ignore the converter code for now. First you need to determine the misfire code. I would suspect plug wires or a failing valve/guide. It is easiest and cheapest to simply replace #4 plug wire. If you have access to a leak-down tester you should check #4 cylinder.

 

As far as the converter is concerned it is common for failure. Yet you have more pressing concerns with the mis-fire.

Link to comment
Share on other sites

Ordered some new wires and plugs. So far the code has not re-emerged. I put in a bottle of fuel system cleaner as well. I'll swap out and see what happens. Car seems strong, so it may have been an anomoly.

 

Thanks for all the input.

 

John

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...