Volvo S60 engine surge while idling in drive after multiple component replacements on Volvo S60

Some Volvo S60 owners report experiencing engine surging while idling in drive, which may be attributed to several factors. These include potential vacuum leaks that can lead to rough idling and surging, as well as faulty or worn-out spark plugs that contribute to similar symptoms. Additionally, owners note that increased load on the engine, such as when driving uphill or using the air conditioning, can exacerbate the surging issue. Problems within the ignition system or lean conditions in the fuel system may also play a role, particularly under load. Furthermore, inconsistent boost levels, even without a 'service engine soon' light, can indicate issues with the valve system. For those still facing engine surging after component replacements, it is advisable to consult a certified mechanic for a thorough inspection and diagnosis.