2002 Subaru Outback idle shake/misfire

THE SECOND YOU LET OFF THE BREAK WILE IN DRIVE THERE IS NO MORE SHAKING EVEN DURING WARM UP WHEN THE SHAKING IS MUCH MORE NOTICABLE

Could be a problem with brake vacuum hose/check valve and brake booster leaking

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

A misfire in a specific cylinder should lead you to check the spark plug, fuel injector and compression.

I don't think it has one but the 3.0L does.

Use the cleaner and spray it while engine is warming up, when the idle smoothes out that's where the leak is.

You can use WD-40 and spray in between the intake manifold and the cylinder head. Also disconnect the brake vacuum hose from the intake manifold-plug it and see what happens to the misfiring.

Leaky vacuum hoses Replace them. If the end of a hose is loose or cracked, cutting it off and sticking it back on may temporarily eliminate the leak. But if the hose is rotten or age hardened, it needs to be replaced. Shortening hoses may also create additional problems. The hose may chaff or rub against other components, or pull loose as a result of engine motion and vibration. Use the correct type of replacement hose (PVC hose or vacuum hose capable of withstanding fuel vapors and vacuum without collapsing). Also, be sure the replacement hose is the same diameter and length as the original.

Carburetor or throttle body base gasket vacuum leaks Try tightening down the carburetor or throttle body mounting bolts. If that doesn't stop the leak, replace the gasket under the carburetor or throttle body. If there is a heat insulator or adapter plate under the unit, it may also have to be replaced depending on its condition. While the carburetor or throttle body is off, use a straightedge to check the base for flatness (and the manifold, too). Warped surfaces can prevent a tight seal, so if you find any it calls for resurfacing or component replacement.

Carburetor or throttle body throttle shaft vacuum leaks Wear here can only be repaired by resleeving the throttle shaft, which for all practical purposes means replacing the carburetor or throttle body with a new or remanufactured unit.

Intake manifold gasket vacuum leaks Try retorquing the intake manifold bolts, working from the center out in the recommended tightening sequence. If that fails, the intake manifold will have to be removed and the intake gaskets replaced.

Sometimes the mating surface of the intake manifold or the heads will not be flat (check both with a straightedge). If warped, the intake manifold and/or heads will have to be resurfaced on a milling machine. Another problem to watch out for here are heads that have been milled or resurfaced to raise compression. To maintain proper alignment between the manifold and heads, metal also needs to be machined off the bottom of the manifold where it mates with the block, otherwise it will sit to high and the ports and bolt holes won't align.
EGR valve leaks If the valve isn't closing all the way due to carbon deposits on the stem or valve seat, cleaning may be all that is needed to cure the problem. Otherwise, the engine will need a new EGR valve.

Leaky power brake booster Replace it. But first make sure it is the booster and not just the hose or check valve that is leaking.

Hook up a vacuum gauge

INTAKE SYSTEM LEAK: with engine running at idle or fast idle speeds needle reads between 3 and 5. Check induction manifold gaskets.

1and 1/2 is excessive replace the mounts and valve adjustment after 500 miles should be done and head/s be retorqued