My 1993 240sx starts up and runs fine. But if i let it sit for like 10-20 seconds without applying gas then the car's rpms will start to go down to like 500 and studer. I think it could be the o2 sensor because i checked the spark plugs, wires, and i replaced the distributor car and rotor and it still does it. Can anybody help?

 

clean maf and tb also the aiv

 

check vaccum lines (seafoam?)

 

if your O2 has a lot of miles, you might want to replace it anyways before you check the other stuff