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The idle speed is controlled by the engine computer through the idle air control valve , there are no provisions for adjusting idle . If idle is to high or you just think it's high , you need to test ,don't guess . Watch this video that shows what happens when you adjust thing's that you should not . Ford IAC valve test how to adjust minimum idle speed How to do it correctly !
If its a simple rough idle consider a few things given you have a Subaru. Your basic spark plugs and even coils at this point with mileage. Goods foundation for well taken care of high mileage cars. The engine has proven its self, just keep taking care of it.
Another thing to check if you do this and its still acting up is Subaru has issues with coolant getting corrosive and "eating" away at the head gaskets. If this is an issue you will have noticed a bit of coolant being lost. Check the spark plugs for coolant contamination Via google images or something. They get very clean because in a sense an internal leak does a kind of steam cleaning in a very distinct way.
Next would be check for an external leak which should not cause rough idle, but low coolant and over heating is easy with your engine design. Air pockets are too easy to get on your design. Do what is needed to keep coolant sealed and air pocket free.
Rough idle should also check vacuum hoses for cracks with high mileage. Rubber cracks and gets weak over this amount of time exposed to high heat of an engine. It just happens, its a rubber product. Silicone hoses are the best if you can get a hold of them. Pricey, but well worth it if you plan on keeping this or any car you plan on keeping to go this long.
Anything else would need more testing that would require different tools and diagnostic evidence to go further.
If you have a high idle and lunging...that usually happens when there is a leak on the intake manifold side allowing more air to get in, then the computer senses the increase in air and adds more fuel. There in turn has to be one more failure in the system to allow the idle to run away, may be a tps sensor (throttle position sensor) or something down the line.
First check for a loose hose or a vacuum leak. If you do not find a leak most likely the throttle position sensor is stuck and causing the truck to idle high. The throttle position sensor sticks, and if this happens you will need to replace it.
ok firstible who recharge the system? you or an autorepair? or are you a mechanic? if you say the pressures are ok, what are the pressures at? and sound to me like the system is overcharge, please answer my questions so we can comunicate better, are you just a car onwer, or are you a mechanic because i see on you ranking than you have it high, that way we will comunicate better,