Join Date: Aug 2018
Feedback Score: 0 reviews
P0303/P0304 Above 70MPH
Most highways here in Washington are 60mph and I typically do the speed limit or about 65. From time to time though, I've been on a few highways out here that are 70mph. My '98 outback 2.5 5spd will do exactly 70 all day with no issues. However, once I push it closer to 80 for passing etc. for more than 30 seconds approximately, the check engine light comes on with P0303/P0304 codes for misfires on cylinders 3 and 4. I've never felt the car shudder or lose power when this happens. It continues to feel just fine.
The first time this happened, I erased the codes and they didn't come back. Thursday I was on one of these highways and it happened again.
I've only owned the car since the summer. As far as I know the PO had the following work done: New front CV axles, headgaskets, timing belt assembly, water pump, radiator, rear brakes, backup light switch, starter, steering rack, oil pan gasket, valve cover gaskets, spark plugs, and all the exhaust forward of the cats all within the last year. Personally, I've replaced the clutch disc, pressure plate, flywheel, clutch fork, rear main seal, clutch master and slave cylinders, shifter stay bushing and shifter joint.
As you may have seen from my other thread, the car has been bucking under 2,500rpm in first and second gear when the throttle is barely being pressed. I don't know if that could be related at all, just throwing that out there.
Sorry if this is a re-post. I swear I saw another thread about this pertaining to the ~70mph issue in particular when I looked it up before, but I can't find it now. Just looking for some advice or suggestions. I don't really want to just throw money at it.
EDIT: Actually checked the codes just now and it's showing P0301, P0302, P0303, and P0304 this time. So all four of them. Coil pack then?
1998 Subaru Outback