ib4 Posted March 10, 2011 Share Posted March 10, 2011 Hello there. I am trying to fix a car for someone, and it's one of those tricky problems: 2001 legacy, 2.5 AT. Symptoms - 1) car misfires at idle, at random, or more frequently so while barely moving at slow speed or in reverse. The misfire is random, more like a single shake once every while, not continuous. Also happens when standing at a stoplight. 2) it also often skips at hard acceleration (at different speeds while driving) - again single shake, then goes up fine, not all the time though. Codes: p0420, p0303 (the 0420 was there for a couple of years now with no issues). So, p0303 - misfire on the 3rd. What I've done so far: Did a "hot soak" by poring some seafoam into the intake. Replaced plugs, checked wires - no visible arching, resistance appears to be normal (3 and 1 lower than 2 and 4). Replaced the coil pack (used part). Checked compression - 195 on both at passenger's side, 180 on both for driver's side. What's next? Fuel injector? Do the symtoms somehow correspond with injector problem? Any suggestions will be extremely helpful. Thank you. Quote Link to comment Share on other sites More sharing options...
bstone Posted March 10, 2011 Share Posted March 10, 2011 Did you replace the plug and wire with Subaru OE parts? If not, go do that. Quote Link to comment Share on other sites More sharing options...
Cougar Posted March 10, 2011 Share Posted March 10, 2011 You could try swapping the fuel injector to see if the trouble moves with it. Changing the knock sensor or the O2 sensor have sometimes helped others with this kind of issue. Quote Link to comment Share on other sites More sharing options...
ib4 Posted March 10, 2011 Author Share Posted March 10, 2011 Thank you. Well, that's a lot of used parts, and since it's not my car... I think I'll start by moving injector around The plugs are OEM, wires were not replaced as I thought I tested them well enough (they are OEM too). Also, forgot to mention, the car had one of the heads replaced 2 years ago (I think the one with higher compression) and for some reason it always seems to perform normal again after I work on it, for a day or so, maybe it's just begging for attention Quote Link to comment Share on other sites More sharing options...
Cougar Posted March 10, 2011 Share Posted March 10, 2011 (edited) Swapping the injector is what I would try also since it doesn't involve buying any extra parts. If you can swap the plug wire also that would be a good thing to do. The compression readings for the driver side are perfect but the passenger side readings are slightly too high. It may be the valve timing is off slightly on that side. Edited March 10, 2011 by Cougar Quote Link to comment Share on other sites More sharing options...
ib4 Posted March 10, 2011 Author Share Posted March 10, 2011 That's what I was thinking. But the car worked just fine after head replacement for a long time now, I don't think it was screwed up than. Just got the call from the car owner, the car is running worse. (just pored a can of seafoam, in the tank this time, yesterday). She wants me to replace the injector tomorrow morning. I suppose will do that, along with maybe moving it around first to confirm the issue. Quote Link to comment Share on other sites More sharing options...
94Loyale Posted March 10, 2011 Share Posted March 10, 2011 First thing to look for on these motors when you have a misfire is checking to see if the rocker covers are leaking oil on the plug wires. When you pulled the wires out, were they covered in oil? Quote Link to comment Share on other sites More sharing options...
ib4 Posted March 11, 2011 Author Share Posted March 11, 2011 No they are not leaking right not (not much to notice wet wires anyway) but they used to heavily before the head work. Does the oil shorts the spark? Funny developments: yesterday I decided to track the problem some more before doing the injector. So I erased the error codes, and they are not coming back. The car jerks, I drove it around but the computer says everything is fine So the P0303 was not even related... some old random fault. Well, the injector version is now obviously false. What I did yesterday is cleaned the ICV - no effect, checked for vacuum leaks (sprayed water everywhere) - no effect, replaced the fuel filter (who knows) - no effect, actually replaced the good tested plug wires - problem went away. I am not optimistic however, the same thing happened when plugs were replaced and when the seafoam was pored into the intake first time. We'll see; if id does not come back in 2-3 days, that's it, otherwise I'll just shoot myself :-\ Quote Link to comment Share on other sites More sharing options...
Cougar Posted March 11, 2011 Share Posted March 11, 2011 Checking the DC resistance of a plugwire isn't going to eliminate the possibility that the wire can be bad. Quote Link to comment Share on other sites More sharing options...
Olnick Posted March 11, 2011 Share Posted March 11, 2011 actually replaced the good tested plug wires - problem went away. Did you replace them with OEM wires? Quote Link to comment Share on other sites More sharing options...
ib4 Posted March 12, 2011 Author Share Posted March 12, 2011 No. But come on, it cannot be that sensitive. It's working fine so far Quote Link to comment Share on other sites More sharing options...
unibrook Posted April 4, 2011 Share Posted April 4, 2011 Did you get this resolved? My guess is you need to replace the front 02 sensor....if it hasn't been done in the last 40k miles. Quote Link to comment Share on other sites More sharing options...
ib4 Posted April 10, 2011 Author Share Posted April 10, 2011 Yes, the problem was resolved with the new wires. Thank you. Quote Link to comment Share on other sites More sharing options...
logic23 Posted April 10, 2011 Share Posted April 10, 2011 You should also replace the front O2 sensor. The 420 code is left over from when the headgasket failed. The O2 sensor gets fouled out and messes up the mixture. If you replace it her gas mileage should improve. I have done a ton of these phase 2 HG jobs and 80% of the time i end up replacing the O2 sensor too. Get a denso or bosch. Both were OEM. Quote Link to comment Share on other sites More sharing options...
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