Misfiring VT Help please

[Anth0ny1oo1]

hi everybody,

I have a 97 vt commodore v6 and it has recently dropped a cylinder. When it is idling, it has a slight miss, then in gear it its quite shakey.
When I am stopped at lights there is sometimes a knock, but not always. (only in gear but at a stop)
When I cruise between 1800-2200rpm it shutters badly and i need to keep it in 3rd gear and keep the revs up close to 3000 to keep it from shuttering.

I have changed the leads and plugs, didn't fix it. Changed the leads again to the Blue heavy duty leads... Didn't fix it, Checked the plugs again found cyl no6 very very black so I replaced it and put the gaps to 1.2mm.

I changed coil pack, all the vacuum hoses, cleaned the throttle body, airflow metre, fuel pump and filter cleaned the tank aswell and it is still misfiring and running badly.

When I take the plug off the 6th Cyl it has spark but the car does not react compared to when I take off the 5th or 4th.

Any help on what could be wrong would be awesome and a solution would be even better

Thanks
Anthony

 

[Anth0ny1oo1]

I also took out the thermostat as it was seized and took the rocker cover off to see whether there was anything irregular and nothing seemed out of the ordinary.
No oil in water etc and no problems with the tranny.

 

[Mick1988]

So the car doesn't react when you take the lead off the 6th plug? Try swapping the injectors between cylinders 5 and 6 and see if your fault moves to cylinder 5.

 

[Anth0ny1oo1]

Thanks for the reply Mick,

I haven't had time yet to swap th einjectors, but if it helps, the sparkplug comes out wet.

This morning I took off the radiator cap and the water was foaming out the top cold. It was like when you shake a lemonade bottle and get the fizziness
Cheers

 

[Tree cutter]

Time to get a compression test done. It could be a burnt valve or broken rings if you are getting spark to that cylinder and your plug gets wet from fuel but doesnt fire. It could be a crook injector too that is just dumping fuel in instead of spraying a mist of fuel.