I have a 52 plate Vectra 2.2 LS (Z22SE engine).
Recently, whilst accelerating (particularly from standstill), the vehicle has been surging. If I dip the clutch, apply more throttle and feed it back in very slowly, it's fine but then occurs again a couple of seconds later. It seems to happen between 1500 and 1800 RPM but has occurred at higher engine speeds from time to time.
The car has not been hammered and I am no boy racer.
It's done 94k, there are no engine management lights (I've also plugged in the diagnostics kit with nothing listed) and I have checked the following:
Plugs - All clean with the correct gap (although the vehicle now has single electrode plugs where it used to have multi-electrode - Halfords say they don't make them anymore and that the single-electrode are the correct replacement and EuroCarParts say the HLR8STEX multi-electrode plugs are the wrong ones for my engine??). I suspect the clean plugs also rule out any problems with the coil pack.
Throttle body cleaned - This was coked up quite badly and whilst there was some performance improvement after cleaning (to 'like-new' standard!), the main problem still exists.
EGR valve cleaned - This wasn't as badly coked up and seems to be functioning freely.
I am now at a loss as to what it might be and would appreciate any thoughts from the forum!
Many Thanks
Mark