Vacuum leak, defective spark plugs or wires. Vacuum leak would be the #1 suspect.
If an alternator is going bad it can cause a rough idle in a 1993 Subaru Legacy. Cold temperatures in the winter can also cause a rough idle in the Subaru Legacy.
Rough idle lacks power
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The power brake vacuum booster is probably failing.
head gasket is gone
Bucks- lack of power- rough idle
why does my vr commodore idle rough when at complete stop
Why does my 2001 kia sportage idle rough?
rough idle smell gas
There are many things that can cause a rough idle on this car. The computer could be going out, the engine may not have enough oil, and the engine may not be getting enough fuel or electricity.
Could be the TPS, it will cause it to idle high and low and make the car become sluggish, but a vehicle will run without one, but it will run very rough.
injectors are a common problem