Update, as it seems that I have been chasing a red herring. I changed both the Lambda sensors, no change. I then changed the crankshaft position sender G28 that works in conjunction with the G40 sender. Still no change. I then changed the MAP sensor, no change. I checked for air leaks and cleaned the TB and EGR valve. The car would start fine on four cylinders and sound ok, but not really super mechanically quiet and after a few minutes, would start to misfire on No.2 with the EML light coming on, before the signal for NO.2 injector would cut out completely. I had presumed it was a signal fault from a sensor telling the ECU to cut No.2, or resistance build up in the engine harness.
Yesterday morning it started as per usual, but the engine was super quiet and smooth with no mechanical noises or misfiring. Again 3 minutes later it started to 'pop' 'pop' 'pop' from the exhaust and the car went onto three.
I had always presumed the roughness and mechanical noise were caused by poor firing or detonation.
I booked the car into my local dealer for a diagnosis yesterday morning. I know the parts guy very well by now, and even though concerned that another local Main dealer had charged 2 hours labour to the previous owner to do a compression test, decided to try my local dealer anyhow.
The workshop manager was not exactly very friendly as I explained what I thought was the problem.
He phoned this morning to say that the car is electrically perfect, but they believe there is a lifter/valve problem on No.2 cylinder.
What I believe has happened is that the lifter is losing its pressure after a few minutes running and the inlet valve is not opening fully, hence the combustion is not complete and the knock sensor or other is picking this up and eventually cutting the injector signal.
I bought an OMD2 wifi sender and use the App REV on my i-phone.
I was picking up high +40% Long Term Fuel Trim, suggesting that the ECU has been trying to compensate for the partial combustion.
I was surprised when the workshop manager said that they did not have to change all the lifters, but only the faulty one.
He was meant to get back to me with a price to do this today.
Can anyone give me an indication please of the number of hours of labour required to change a lifter.
I imagine the procedure is: Cam cover and ancillaries off, cam belt off, cam off revealing the lifters?
I read on another thread about £600 or so for a complete change of all the lifters.
Any guidance most gratefully appreciated.
Cheers, Philippe