QuestionSo far, no CEL, no codes. I did
pull the wires off the coi and tower number 4 looked a
bit different than the rest. Also pulled all plugs,
inspected and regapped. No visible problems. I am
running the stock NGK plugs and they have 10-15,000
miles on them. They looked like the engine had been
running quite lean although I've noticed in the past
that Subaru's engine management likes to keep things
quite lean. The problem seems most evident at an idle
and during acceleration from a stop - the engine wants
to sputter and misfire making it hard to start driving
on a hill. The problem probably doesn't go away at
higher RPM's but is not noticible.
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The text above is a follow-up to ...
-----Question-----
I have a 1999 Outback with the DOHC 2.5 engine and manual transmission. Periodically, my engine hesitates or misses while idling. The hesitating continues as I accelerate and then goes away. I checked the plugs, filters and all of the usual suspects and found nothing. Any ideas or suggestions as to what's causing this.
-----Answer-----
Check engine light on? Any codes? Have you pulled the plug wires off at the ignition coil? We have seen corrosion at the coil towers where the wires attach. How many miles on the car now? Even though the plugs may look good, if they have been on for over 60,000 miles I would replace them with new NGK plugs. Are they NGK plugs now? If not, I would put new NGK plugs in. Worse cold? Hot? When it goes away, what has to happen for it to come back?
I know, lots of questions and not many answers. Sorry. But, if you can get back to me, we might be able to figure this one out.
AnswerSounds like you might have a bad coil. The problem you describe is often fixed with the substitution of known good parts. Our techs would probably switch the coil with a known good used coil. If that fixes it, then you are done. If it doesn't, some time of engine decarbon might be recommended to remedy the possibility of carboned valves sticking. Also, the heads might be pulled to see if you have a valve guide that has started to move. According to Subaru, if you have that problem, you can drop the exhaust and see it, but we have never had that luck. And finally, the new Subaru Select Monitor III or SDS may help find this problem, but only a Subaru dealer will have it. Subaru techs have fought this type of problem for a long time since misfire data is not cylinder specific on the Select Monitor II. And, it may not be available from your older on board computer.
Sorry, I don't think I am going to be much more help to you. Try a coil. Try a Subaru dealer. Considering how car savy you sound, I really hate to not give you better advice.
Good luck, and if you come up with more, I will run by our techs on Monday.
Z
