1997 Legacy intermittent misfire - safe to drive long-distance?

[jeffseymour]

*Edit: For posterity, my verdict is no, not safe to drive long distance. Car died 5 miles into the return trip. RIP. Wish I'd gotten the engine fixed or replaced before I burned my catalytic converter up.

 

Hi all,

 

I've been lurking on this forum for years, getting advice on various little issues with my car, so first off: thanks.

 

I've got a 1997 Subaru Legacy L, 2.2L, manual transmission. Car has 219k miles, and it has a rebuilt engine with (I think) around 110k on it that was dropped into the car about 40-50k miles ago. My numbers here are fuzzy because I bought the car after the rebuilt engine was put in.

 

For the most part, it runs like a charm, but a couple of years ago it started throwing intermittent P0302 misfire codes. Every once in awhile (usually climbing a hill, but not always), the CEL will flash, and the engine will lose some power. Usually downshifting and revving the engine high causes the CEL to stop blinking and the power to return, but not always. When this happens, the car will sometimes run real, real rough (shaking like someone's outside pushing on it) and flash the CEL at idle, but then run fine at higher RPMs. It always fixes itself eventually, clears the CEL on its own after I drive it far enough, and then runs without problems for a while.

 

Based on this thread and the advice of a mechanic, I think it's probably a burned exhaust valve. But fixing one of those is a little outside my expertise (not to mention tool set), and it's a pretty expensive repair for something that might not fix the problem, so I've resolved to just drive it until it either dies or the problem becomes more pronounced. It is getting more frequent---it was probably six months between the first time it threw the CEL and the second, but now it's more like a once a month kind of deal.

 

I'm not worried about it driving around town, but I've got two cross-country trips planned for the summer, and I don't want to get stranded in the middle of nowhere at the mercy of some mechanic who's got no reason not to rip me off. It's my only car, so I can't just take another. So I'm wondering---is this a problem that's likely to keep getting worse slowly over time, or is it the kind of thing where one of these days it's just going to die on me?

 

Thanks.

Edited June 9, 2014 by jeffseymour

[Fairtax4me]

Not that its unheard of but I wouldn't put money on a burned valve until youve checked everything else that makes the thing fire.

 

Two major points to consider.

1. How long ago did it last get plugs and wires? This is the number one reason for an intermittent misfire. Standard copper plugs will be worn out in 50k miles. If it hasn't had plugs in the last 25k, its probably worth it to check them.

 

2. A burned valve will first show up at idle, and they are NOT intermittent. Once a valve is burned its burned for good. Ot doesn't fix itself or get any better.

 

 

That said, the valve lash on that engine is easily adjustable. It would be worth-while to check it.

[jeffseymour]

Plugs we changed about 5k miles ago, so we know it's not them, and they were clean when we pulled them, so I don't think it's a plug issue. The mechanic tried swapping out wires and distributor coil while trying to diagnose and said the problem persisted even with replacement parts swapped in. I checked resistance on wires too, and they came up fine.

 

Will look into the valve lash. If it's not a burned valve (because it definitely comes and goes---right now it's running fine, no CEL), any other ideas?

[1 Lucky Texan]

can you move the wire, plug and injector to a different cylinder?

 

how about a leakdown test?

[Fairtax4me]

If its always the same cylinder its possibly the fuel injector.

Those are a fairly easy swap but you do need to clear the fuel rails before pulling the injectors out or all the fuel in the rail will dump into the first one you pull.

[Rooster2]

Agreed, a burned valve does not produce an intermittent problem. It would produce a constant reminder that something was wrong. 

 

You may want to consider renting a car for your trips. Shopping car rental agencies on line with discount codes can produce some good low rates. Makes a long trip more fun driving a new car.

[jeffseymour]

Thanks again for the help. I'll look into the fuel injector along with valve lash, possibly this weekend. Anything I should look for in particular when I pull it?

[idosubaru]

swap fuel injectors and see if the misfire moves with the injector.

 

valves are easily adjusted on this engine.  0.010 exhaust and 0.008 intake.

 

the plugs and wires can be suspect, but i think you swapped those around already?

 

these engines ***will*** produce misfires with non-OEM plugs, best to use NGK stock plugs, and with brand new wires.  I've seen Subaru..including that exact same engine in a 1997 Impreza OBS have misfires with brand new plug wires.  They were brand new, no issues, these EJ engines tend to be less forgiving than older Subaru engines in terms of plugs and wires.

 

I'm not saying it is the plugs or wires, but don't disregard that concept too quickly on such an unforgiving engine.

[jeffseymour]

Update here: Didn't have time to pull the fuel injectors before we left (now kicking myself over that). Car ran fine for the first few hundred miles---CEL cleared itself. Then about a hundred miles later, CEL came back on and stayed solid for the rest of the trip until we hit the mountains in upstate NY. Got flashing CEL going up real steep hills when the engine was under a heavy load there, and was able to mitigate the problem by getting a good run on the hills, giving it plenty of extra gas, and revving the engine high (CEL wouldn't flash if I could do all those things).

 

So the car got me out, and now I just have to get home again. We burned a quart of oil coming out (about 750 miles), and the mechanic I took the car to in January mentioned compression was a little low on cylinder 2 back then. So between those things I'm thinking it's probably a compression issue (bad rings, cylinder wall, something like that). Going to try to put together a magic cocktail of additives that will get us home, then look into a replacement engine once we're there.

 

Anybody had a good experience with a particular additive or mixture of them as far as restoring compression on a bad cylinder?

[jeffseymour]

Just to wrap this up: added a can of RESTORE engine restorer to top up the oil. Meanwhile I accidentally left the dome light on, the battery died, and the CEL cleared. Car ran great for short and medium-length test drives (no CEL, no loss of power) after I jumped it, and it looked like it was going to get us home. Loaded it up fully today to start out, and on a long (like 2 miles), steep hill, the CEL started flashing and the car began to lose power. There was no good place to pull over, and by the time we got to the top of the hill and I could get onto the shoulder, things were pretty cooked. Smoke in the engine compartment (and blowing into the cabin). Came from the catalytic converter, which had a big old scorch mark on top. Turned the car off, waited a few minutes, started it up, smoke again. At that point, I figured it wasn't going to make it the next 715 miles home. It's now sitting in a field, waiting to be sold. :-(

 

Maaaaaybe I'll look into repairs, but at this point I doubt it's going to be worth it. Either the cat itself is melted (plus the cylinder problem still needs to be fixed), or the engine spewed so much of something onto the cat that something big must've blown. Maybe both.

 

I'm kicking myself for not fixing this before I left home, because I loved this car. So the question I asked at the beginning is, for me anyway, definitively answered: no, not safe to drive long distance. Hope that saves someone else some pain in the future.

[Fairtax4me]

Pretty good bet the cat melted inside and is now toasted, but those can be "fixed", at least well enough to drive it home, with a hammer and a tire iron. Of course you need some tools to unbolt the cats from the y-pipe so the tire iron can be shoved inside.

 

Misfiring dumps raw fuel into the exhaust. Catalytic converters don't like raw gasoline. It makes them heat up, and keep heating up. Eventually the substrate of the cat will melt and clog the exhaust. If overheating is severe enough the cat can catch fire and set the car on fire.