I have a '96 outback with the 2.2L and 5-speed.
It started misfiring under load and finally threw the P0302 CODE. It happened right by the parts store so I just cleared the code and it didn't come back right away. Still misfiring under load but not bad. I looked under the hood after dark and there was no arcing or sparking of the plug wires even while misting water around the coil.
After a couple of days the code came back. It was finally the weekend so I had time to pull the plugs. They all looked like the text book picture of what a perfectly firing plug should look like but were hugely over gapped, probably near .060". I regapped them and put them back in to see what would happen.
That made a big difference. It was running way better. It still felt like I could make it misfire or stumble or whatever by intentionally lugging it in too high a gear, so on the way home from work yesterday I bought new NGK's and went home to change them.
Of course since I was in a hurry the first thing that happened was that the plug wire pulled out of one of the spark plug terminals. I didn't have time to go buy new plug wires so I repaired it the best I could with a screwdriver and needle nose pliers. I'm going to order up a new set of NGK wires this morning.
NOW to my main point. It wasn't until after I had a couple of the plugs in that I noticed I had purchased BKR5E11 plugs. The plugs that came out were BKR6E11. I just put them in, put everything back together and took it for a quick run on the highway. It ran AWESOME. No sign of misfire or stumbing under load.
So this morning I am doing some research and I get conflicting information on whether the 5 or 6 is the right plug to use. It looks like it probably should have been the 6. Interesting that if I go to the NGK website and punch in the 2.2L for the '96 outback it tells me to use the 6, but if I punch in the 2.5L it tells me to use the 5. I also found this part number decoder which I thought was pretty cool:
So I am thinking that I probably should have went with the 6, especially since the 6's that I took out looked like the text book picture of what a plug should after around 100K miles. Do the experts agree that I should be using the 6's?
Is running with the hotter 5 plug really that big of a deal? Do the experts think I should eat the $10 bucks and buy a new set of 6's to go with the new plug wires? Or should I not worry about it and just go with the 5's?
Thanks to all who bothered to read this far. I have a tendency to write novels. And I did do a search first.