cnc Posted September 12, 2012 Share Posted September 12, 2012 From time to time, it has a really rough idle, but then fixes itself as if by magic. No engine light. Checked intake vacuum and is 21. Watched gauge while wiggling all vacuum lines I could find and nothing changed. Was working fine before I took it into the shop, and immediately afterward, it started doing this. Suspected a cracked vacuum line, but can't find one. Shop was fixing the oil leaks on top of cam carriers and belly pan. Lines had to be removed while working, so maybe something went bad then? Mileage was and is still high 20's. Tried different gas, 2 tanks each. No change. Idle is so rough that other passengers comment on it, like "what's wrong with the engine?", then it fixes itself.http://www.ultimatesubaru.org/forum/images/smilies/popcorn1.gif Ideas? Quote Link to comment Share on other sites More sharing options...
lmdew Posted September 12, 2012 Share Posted September 12, 2012 You can try spraying WD-40 on the lines while the engine is running. If there is a leak, it will pull the fluid in and the idle will change. Does it happen at a specific time or condition? If it just came out of the shop, I'd head back there and have them correct the problem. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 12, 2012 Share Posted September 12, 2012 triple check the PCV and breather hoses for misrouting. something wonky with the evap system or possibly fuel related? weird Quote Link to comment Share on other sites More sharing options...
cnc Posted September 13, 2012 Author Share Posted September 13, 2012 Good questions and tips. The problem gets worse when it gets up to temp. If it's cold, it almost never exhibits this problem. We took it in with lots of fuel in it, and the problem started a few blocks down the road from the shop, with the same gas in it. The only thing that was worked on was resealing the cam carriers and the belly pan. Other things were no doubt removed and put back on, though. Everything looks like it is hooked back where it should be, in general. I started up the car tonight and wiggled every vacuum line I could find and got no change in the smooth idle at all. Runs like a top most of the time, but then goes nuts on the rough idle for a little while (minutes) and then straightens up and flies right again. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 13, 2012 Share Posted September 13, 2012 maybe a crank angle sensor is getting intermittent with temperature? maybe scan for pending codes after an 'event' - intermittent stuff may need to happen twice within a short period to set the CEL, but single occurrences would be stored for a little while as 'pending'. Quote Link to comment Share on other sites More sharing options...
danbennett2u Posted September 13, 2012 Share Posted September 13, 2012 possibly plug wires damaged and arcing intermittently? Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted September 13, 2012 Share Posted September 13, 2012 I agree with others that there is a vacuum leak somewhere. Spraying WD-40, or using a squirt gun filled with water on all vac lines may show you were the trouble is. I would spray along all vac lines, as it may be a line that has a split in it Quote Link to comment Share on other sites More sharing options...
davebugs Posted September 13, 2012 Share Posted September 13, 2012 possibly plug wires damaged and arcing intermittently? If no vacuum leak 2.5's are picky about plug wires. They like OEM best. What can you tell us about the plug wires? Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted September 13, 2012 Share Posted September 13, 2012 I had identical situation in a non-Subaru car; my Wife's "KiaStein" was acting like that, then after searchin' I found a Loose Plug in the wires that connect to one of the two the Ignition Coils... Somehow when the engine got hot, as metals expand, the plug becomes more loose. ... 2.5's are picky about plug wires. They like OEM best ... ...good advice, have you Checked those? Could you stop and pull to one side of the road (to a safe place) when the Engine starts acting, and then open the Hood to check those Wires? ... also you can move the Hoses to see if that corrects the failure. Good Luck! Kind Regards. Quote Link to comment Share on other sites More sharing options...
torxxx Posted September 13, 2012 Share Posted September 13, 2012 If a plugwire is misfiring to the point where its actually idling rough and not just having a EJ25D stutter, you should be able to hear the spark grounding out. Check the coilpack tips as well, they like to turn green if you live anywhere with any moisture. Quote Link to comment Share on other sites More sharing options...
cnc Posted September 13, 2012 Author Share Posted September 13, 2012 Good tips. I was told that if there is any misfires, that will turn on the check engine light. It has never come on. I will try the wd40. Are you sure that still works? I think they changed the propellant, cuz it no longer works in potato launchers. I'll check the wires. They were not changed out at that time. Is the crank angle sensor something that would have been messed with while changing the cam covers or oil pan? Quote Link to comment Share on other sites More sharing options...
davebugs Posted September 14, 2012 Share Posted September 14, 2012 I've experienced an idle miss that didn't turn on the CEL (sometimes not even a code "pending"). For the vacuum leak test I've always used carb cleaner - it's plenty flamable but haven't needed to take that route in a long time. Crank sensor didn't need to be touched for oil pan or cam covers. And the wireing to it shouldn't have been touched either. Did I miss it? What BRAND are the plug wires and how old? Quote Link to comment Share on other sites More sharing options...
cnc Posted September 17, 2012 Author Share Posted September 17, 2012 Hi, I don't know the plug wire brand. Will look it up. More clues: Idle does not kick up when AC is turned on. It should. When engine misses, it's instantaneous, like an electrical problem, not a fuel starvation or over-fueling. Wires were not changed at the shop. Goot-n-tight at the central distributor. Fingers too fat to check at the plugs. Quote Link to comment Share on other sites More sharing options...
jboymechanic Posted September 17, 2012 Share Posted September 17, 2012 I would look into your Air Idle Control valve. Quote Link to comment Share on other sites More sharing options...
cnc Posted September 18, 2012 Author Share Posted September 18, 2012 I've never checked one out. I can look for it in the manual. What will I be looking for, broken hoses, loose wires, bad connector, fuse? What should it be doing normally? Like I mentioned, the fast idle doesn't come on when you turn on the AC. Thanks. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 18, 2012 Share Posted September 18, 2012 Loose spark plug wire. Misfires do not always trigger a CEL right away. Check plug wires first. Any that aren't clicked on all the way can cause problems just like this. Also entirely possible that one was damaged internally during removal. The conductor can break where the clamp is attached and you would never know without taking the boot off. Quote Link to comment Share on other sites More sharing options...
wally Posted September 18, 2012 Share Posted September 18, 2012 any thought that it could be a partially plugged injector? my '95 recently had similar symptoms. car would noticeably rock at idle, sounded rough, but ran as well as always "at speed". just like popcorn. the other day, it started being sluggish under load, at all rpm. i drove it hard for a few miles, with lots of "missing" and lacking power, at about 5,000 rpm. after a few miles, it stopped doing the missing, and power returned. it idles better than it has for a month. i have no idea what really happened, but if it was a single injector, the obstruction could have finally passed. :shrug: oh, and my CEL was flashing fairly regularly for several days leading up to the rough running under load, numerous times during a 100 mile trip. since then, no flashing CEL. Quote Link to comment Share on other sites More sharing options...
jboymechanic Posted September 19, 2012 Share Posted September 19, 2012 The AIC valve controls the amount of air entering the intake manifold when the throttle valve is closed (at idle). Over time, the valve can become clogged and cause rough idle. I would look for another one at a junk yard, or maybe swap one off another car that has no issues and see if the issue remains or if it follows the AIC to the other car. Quote Link to comment Share on other sites More sharing options...
cnc Posted October 3, 2012 Author Share Posted October 3, 2012 Took it back to the shop and it works fine, now. Turned out to be bad wires and bad plugs, according to them. They were decent enough to not charge labor for the installation, but I still don't know how a vehicle can be working fine as it pulls into the shop and start missing as soon as we pull out of the shop and be attributed to wires/plugs that suddenly (??) go bad. It was in for sealing up leaks on the camshaft covers and oil pan. Don't the plugs need to come out to do that? Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted October 3, 2012 Share Posted October 3, 2012 What constitutes a "Bad" plug wire can vary, but as I said before, the part that fails is not always visible to the eye. Internal breaks in the conductor strand or a poor connection between the conductor and the clamp in the boot can cause intermittent issues exactly like what you described in the first post. The plug wires could have also been damaged when removed by the shop. Spark plug wires aren't usually very tough, and it's pretty common for the clamps to come undone when removed, especially on low quality or old wires. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.