What do you mean by ' loose motormount'? is an attachment bolt missing? How did you determine it is loose?

Mounts usually fail by leaking damping fluid until they are too compressed to function properly (but not 'loose') - or a bolt comes out and can be replaced.

If a U.S. model, the 4-cyl is a 2.3.

Check the plug make/model, because if Bosch Platinums, they are incorrect.

Idle issues can be researched here, and in this older model, have many possible causes.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7