S type with 50000 miles 3.0 petrol 

just replaced the auxiliary belt which was easy. Put everything back together and now it’s misfiring at idle and acceleration and now the engine light has come on. 

Ran fine before this, I checked everything and all is back as it should be. All that was removed initially was the air box pipe.

hi

easy way is to get codes read and it will point you in the right direction

but its going to be a pipe off or bad connection, check the maf connector on the air box

4 hours ago, JOE-DOT-COM said:

hi

easy way is to get codes read and it will point you in the right direction

but its going to be a pipe off or bad connection, check the maf connector on the air box

Just bought a code reader, hopefully it’ll throw something up

The code reader was £20 and showed a misfire in cylinder bank 1. 

It transpired that the spark plug was full of water. Changed spark plug and all sorted. It was just a coincidence the fault occurred after the work I did on the belt which was all good (easy job by the way).