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Old 09-29-2008, 01:50 PM   #1
brian3676
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Member#: 167849
Join Date: Dec 2007
Location: Portland,OR
Vehicle:
2000 Impreza 2.5rs
Blue

Default 1996 legacy rough idle, tried everything I can find

Well my GF has a 1996 subaru lagacy 2.2L auto, 178K miles.
Drives perfect and idles very smooth in park and nutural. However when in drive and we come to a stop light or sign it gets very very rough and sometimes (once a day maybe) starts to shake violently like it has a temporary mis fire as if the wires were put on backwords or something. when this happenes the engine light starts to flash then we accelerate and it stops flashing. All maitnence is done on it, plugs, filters, tans flush and all that good stuff, tested the wires and they were fine (ohm reader) I heard low compression could cause this? yes the engine light is on and we scaned it and it told us the CATS are bad but i was told the o2 sensors are really the problem so i replaced both front and rear o2's. engine light still on but just says cats are still bad. Any advice? thanks brian!
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Old 09-29-2008, 02:37 PM   #2
fubart
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PCV replaced?
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Old 09-29-2008, 02:42 PM   #3
brian3676
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yeah basically everything under $50 that would be part of matience is new as of 2 monts or so, i have tried replacing everything besides the cam, crank, maf, knock and coolent temp sensor cuz there $ and i want some advice befor i spend $200 haha
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Old 09-29-2008, 05:05 PM   #4
oldhat
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Try cleaning out and relubing your Idle Air Control Valve (IAC). I think the '96 Leggy has the old style one that tends to get fouled with deposits over time. Search around for "iac cleaning" North Ursalia's posts on this forum and also on scoobynet.com.
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Old 09-29-2008, 06:12 PM   #5
fenderman07
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I would pull the Ypipe down and look up at the valve guides in the heads.
These have a nasty habit of dropping the exhaust guides over time and holding the valves open. They should all stick out the same amount. It usually starts out just this way. Or you could try some GM combustion chamber cleaner. This might clean up some carbon on the valve stems temporarily and solve your problem. If the CEL flashing and the misfire lasts long enough you should be able to pull injector plugs off one at a time while idling and see which cylinder is causing the problem.
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Old 09-30-2008, 04:14 PM   #6
John*G
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95 coupe
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I would check for vacuum leaks (free). I don't know if you can check wires with a ohm meter as you are really looking for shorts in the insulation not continuity, so you might want to replace them.
John
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Old 09-30-2008, 04:57 PM   #7
yarrgh
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if your CEL says the cats are bad....well, 178K miles. maybe they ARE bad.
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