i own a 1990 240, after a long freeway drive 40 min. or so the car starts to run horribly when at a light or at low speeds. and starts to run rich, black smoke out the tail pipe. but if i drive shorter distances the car is fine and pulls no codes. after a long drive it picks up codes 113, and 232 this is a code for the injectors and oxy sens.
so far i have replaced:
fuel pressure regulator
coolant temp sensor
spark plugs (spitfire)
the AMM and the egr valve were tested and said to be good
i was wondering if the wires or mabey the spark plugs, the 02 sensor was changed not to long ago, mabet 50,000 miles, could the o2 sensor cause these problems, any advice would be great i cant really afford the expensive volvo mechanics and need a car to get around thanks again