My V6 One Tonner has been running rough and having trouble starting for a while now, and the last week or so it has been running horribly rough below 1500rpm and getting 21L/100km.

Yesterday my mechanic replaced the coils and plugs, and found one side were black, and one plug was wet - obviously that coil or plug was dead and not firing. He said that unburnt fuel usually kills the oxygen sensor, which leads to running rich, so he replaced the sensor on that side too.

This morning I found that the roughness is back, from idle to 1500rpm, though not as bad as yesterday. Starting is still iffy - sometimes clean, sometimes jerking and farting before settling down.

My mechanic's lining up a visit to someone who has a diagnostic tool, but that could take a few days to get in.