93 legacy wagon

When my car is cold it runs great,but after it gets warm up it act like it wants to shut off or runs at a low rpm's (500 -750) . when driving on the road at 50 -60 mph it runs good but when you slow down it spits and sputters and the engine light will come on every week or two for about 1 miniute then go back off ? I have check the for a code and the engine light would even come on for a code .thanks It has 145,000 miles on it Could it be a 02 sensor ?

I have a 90 eg22 in my vanagon and it acts like that-- I suspect fuel--and it developed the electrical dying thing at speed too, so i am replacing the igniter with a boneyard one and some of the other sensors too--its a stupid emotional cycle when you test drive for a problem,--you get to the onramp thinking its gone and flutter--it isnt. persistence and a read of the codes will tell.