[colsin]

I have a 1999 subaru legacy outback. I had the check engine light come on codes reading P0303 and P0304.

I have changed the spark plugs and spark plug wires as well as the ignition coil. But the problem has persisted. Any suggestions? The car has lost a lot of power and is rattling while it idles.

 

[eagleeye]

head gaskets done or undone,? (any overheating, or smell of coolant at the exhaust)?

engine grounds,...all nice and clean?

 

[eagleeye]

another thought,

the alternator on these EJ25D and EJ22 cars was recalled a while back.

subaru made many remans for them and only want $75 for one at the dealer. (parts stores can and will give you a less desireable product).

did you put NGK plugs on? what kind of wires / coil? (NGK, or something subaru sold hopefully).

 

[plain OM]

1999 uses a separate igniter to trigger the coil. If I recall correctly, it's mounted on the firewall behind the engine in the engine compartment. Like the coil, it functions on pairs of cylinders, i.e., 1 & 2, and 3 & 4, so the symptoms fit. There's been cases where the igniter would cause misfires at higher rpm. One possibility.

 

[johnnyidaho14]

My son's 99 outback is having similar issues. Originally was seeing misfires in all four cylinders, new spark plug wires installed. Head gasket was previously replaced, as was the alternator due to a fire in alternator. IDK if the alternator is OEM or if it can be replaced with the recalled alternator. As of late my son again was getting codes regarding # 1 & 2 cylinders misfiring, took it to "subaru" service shop in Bozeman, MT who replaced the spark plug wires as they said they were fried due to old spark plugs. When on the highway on two days ago again getting flashing check engine light at higher speeds. At this point don't know whether to get out of vehicle as we're already into it for a bunch of cash with new head gasket as well as other items. Please advise the information regarding spark plugs and igniter if these need to be renewed and if they should be OEM, thanks in advance.