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Rough idling in 99 Forester
Posted 16 June 2003 - 03:26 PM
There are really three symptoms here that may or may not be related:
1. When the car starts, the RPMs stay high for a while before calming down, rising and falling btw ~1100 and 1600 for at least a couple of minutes before descending below 1000. If I step on the gas, they quickly settle down to ~1000, pause there for 5 or 10 sec, and then drop to typical idle range.
2. Idle speed seems a bit low: tach reads ~600 (though I understand this may be lower than the actual RPMs).
3. Idling has a smooth "background," but is punctuated every 2-3 seconds by rougher vibrations, enough to rock the car slightly. What I see under the hood: the engine is jerking about a horizontal axis running from its front to its rear.
Context: I recently had a bad front crankshaft oil seal replaced at the dealer here in Oakland. While they were in there, I had the oil pump resealed and the cam belts and timing belt replaced. I don't remember noticing the rough idle before the timing belt job, but I hadn't owned the car for long at that point (weeks), and I can't be sure the idle problem cropped up then. Can't remember if the idle speed was different beforehand, either. The revving on startup DID occur before I had this work done on the car.
In an attempt to improve the idle, I replaced the fuel filter, PCV valve, and spark plugs & wires (latter three were all original by the looks of it). The revving on startup has improved a bit, but the idle is the same.
I have driven other Subarus with boxers, and the idle was not this rough. Are there other things I should check/replace, like the O2 sensor? Should I suspect a sloppy timing belt job? Any help would be appreciated.
Posted 16 June 2003 - 04:27 PM
Next I'd look at the IAC valve, and possibly a failing O2 sensor.
Posted 16 June 2003 - 05:40 PM
Posted 17 June 2003 - 06:50 AM
When I park after coming back from a trip, the car idles at around 600-650.
I really thing this is quite normal but I could be wrong.
Posted 17 June 2003 - 08:48 AM
If you have no codes for a clue as to the location, you may be able to track the problem down by removing the injector wiring, one cylinder at a time, to see if that will give you a clue as to which cylinder is having the problem. I think you have sequential injection so you can do this. You could also remove one plugwire at a time to help find it.
Hopefully it is carbon buildup, like Josh said, and using a fuel cleaner may help eliminate the problem.
Posted 17 June 2003 - 01:51 PM
BTW, is there a site, or a thread somewhere on this board, that has a list of error codes & procedures for accessing the ECU, retrieving codes & clearing?
Will report back.
*** [time passes] ***
After having the injectors cleaned with one of those 3M setups, the background idle was smoother, and acceleration had improved, but the "hiccups" in the idle that shake the car were still there. The revving at startup has now calmed down to a normal warmup routine.
I also removed and cleaned the IAC valve, which was a little gunky but not too bad. No noticeable difference after doing this. Maybe I'm being too picky, and this is just how the engine is going to idle.
Glen, is there no way that disconnecting plug or injector wires one at a time could damage the engine?
Posted 18 June 2003 - 03:08 PM
But pulling one spark wire kills 2 cyls at a time due to how it's wired. You'd almost want a "dummy plug", grounded to the car, to move that wire to in order to let th other cyl fire.
Posted 24 June 2003 - 09:44 AM
Posted 24 June 2003 - 06:04 PM
Posted 26 June 2003 - 03:55 AM
Posted 27 June 2003 - 01:31 PM
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