Volvo AWD S40-V40 Forum

After selling my 1996 960 doing 24mpg i now have this 1998 V40 T4 1855 200bhp...i really really like it especially the computer telling me on the motorway 38mpg at 90mph....i bought this scanner as the idle was low with a miss now and again and faily rough....the code came up Po340 camshaft position sensor signal missing i erased it about 3 times over a time of 4 hrs and it has gone.. hooray!...but at the same time i have the service light on and the Lamda light on...after 2mins the service light goes out but i cannot erase it myself with the odometer trip lever....i put in the new o2 sensor for code Po141 front sensor....erased the light ..OK..but after 30 secs it is back again and the idle is still missing and rough......Any ideas from here?.....it has new Volvo plugs just put in and new air filter the throttle and iac unit cleaned....