My 89 240 is giving me the 2-3-1 error code and Bently translates this to: "fuel system compensating for rich or lean air/fuel mixture at cruise," The car has 190,000 miles and has been running fine, but lately I noticed a slight lack of power when accelerating. I believe it to be running lean, there is no soot in exhaust pipe and when checking the plugs they look very good. When cleared, the code comes right back, but if the battery is disconnected, it takes about 30 miles to come back. When I purchased the car over a year ago, the following parts were replaced: intank fuel pump, fuel filter, FPR, New/clean flame trap system, air filter, cap, rotor, wires, plugs. I have checked the intake hose for holes and found none, the throttle body is very clean. The car now has a new O2 sensor, due to age, figured a new one could not hurt and I swapped the main fuel pump with a working used one, so I don't think fuel pressure is a problem. Any suggestions on where next to look for a solution to the 2-3-1 problem? Thanks.
Aaron