Hi,

I own a 1991 240 with about 215KM. The only ongoing problem relates to air\fuel mixture resulting in a little rough idling. I took it to several mechanics including a Volvo dealer who were successfull at resolving the problem by replacing the parts thought to cause the problem (O2 sensor, RPB sensor, Air control valve, air leak tests, AMM checked fine) but unfortunately the problem keeps resurfacing after about a few weeks.

Although the check engine light was not triggered the ECU detected air\fuel fault codes. Therefore I made an appointment with a different mechanic for this coming Monday Dec. 6. While driving today my check engine light came with a fault code 221 (extremely rich air\fuel mixture). Although I reset the ECU the check engine light immediately comes after starting.

My question is that if I wait for my appointment on Dec. 6 will I do any damage to the catalytic converter or some other component as a result of the air\fuel problem? There is no smoke coming from the exhaust nor do I sense a loss of power under acceleration.

Also is it possible that a faulty coolant temperature sensor could be the cause of the air\fuel problem?

Any advise is greatly appreciated. Thank you