My 2002 Outback has developed a very strange misfire recently, and while it probably inst a Subaru specific issue (I don't think at least), I wanted to ask y'all for help since y'all haven't done me wrong yet.
The misfire started last week, it wasn't too bad at first, but got progressively worse and worse up to the point where it was feeling down on power, and stuttering to the point where it would almost stall out when moving away from a light. There was and still is no check engine light, it stuttered like crazy moving off from a standstill, it backfired like crazy, and it developed a small tapping noise that sounds like either an injector, something else top end, or even a small exhaust leak when I was moving/accelerating. I started running through the procedures of figuring out what the issue was, and I had narrowed it down to bad gasoline since I had filled up from a station that ran its tanks dry and had their pumps sitting for a few days. I threw a can of Sea Foam into the tank later in the week in the hopes that it would help fix any weirdness in the fuel. It did help, so over this past weekend I refilled from about half a tank and drove 300 miles round trip to my hometown and back to run out the tank and squeeze out any junk in there. While I was in town I pulled the spark plugs on the passenger side as well as the injectors. They were acceptably clean upon visual inspection, so that sealed the deal for me that it was a fuel issue (I didnt get a chance to flow test the injectors since I didn't really have the time/money to see if they were up to snuff however.) I also checked the plug wires and there were no breaks in them, they haven't been shorting on anything, and the contacts looked clean.
When I returned back to town I refilled from very nearly empty, and drove it around town a bit. It was a night and day improvement, it didn't stutter anywhere nearly as bad, (the coupled of times it did stutter it was quickly killed off by adding more gas when moving away from a light), and even the tapping noise had either gone away or had quieted down to the point that I couldn't hear it. So, I thought everything was fine and dandy, I went ahead and poured another can of Sea Foam into the tank to stabilize any bad fuel left in the system, and called it a day.
However this morning when I got in to drive to class, the stutter and tap had returned in force. What was interesting about this round is that it subsided quite a bit once the motor got some heat in it, and the noise was either very quiet or non existent. There still isn't a check engine light either. I'm pretty thoroughly stumped by this. I'm good with a wrench, but I cant diagnose to save my life so any help will be greatly appreciated.
Just a little background on the car to make things easier (hopefully), it has 177k miles on it, it has had head gaskets done in the last 20k miles, O2 sensors replaced in the last 5k miles, and I just put a new catalytic converter on it less than 1K miles ago. It's also had the fuel filter replaced at some point, although I have no idea when. This thing has seen a pretty hard life, so honestly anything on this thing breaking wouldnt surprise me at this point.
Thank you all in advance,
Edited by ayykimber, 25 September 2017 - 10:08 AM.