2002 Corsa Sxi running lumpy on tickover

[jonnyp55]

hi

my corsa runs lumpy on tick over (hot and cold). Runs better when the revs are increase to 2500 and above. Fault codes are P0300 - random mulfiple misfire, Also showing codes P0301 - P0304, misfire cylinder 1-4.

I've replace the plugs and coil pack but its just the same.

Next Ive been advised it may be the ecu, does any one agree?

Where should I go from here?

thanks

 

[Mursal]

Usually not the actual ECU, more likely a faulty sensor or you are getting
air into the inlet manifold from a leak.

Look for cracked vacuum pipes that may be leaking air.

Fuel tank vent valve may be leaking. It allows fumes from the tank into the
engine under certain conditions. It may be stuck open.

 

[jonnyp55]

Hi

i have noticed an inch long crack in the exhaust (outlet) manifold,

that wouldn't be the problem would it?

ta

 

[jonnyp55]

Further information. I carried out a compression test on the vehicle and found the compression on cylinder 1 to be down.

The car is now in a local garage getting the head taken off. I'm hoping its a valve not seating properly!