Thanks for the responses so far. Sorry, I should have pointed out that it is carburetted, not fuel injected. Some extra points I should also make, the misfiring just came out of the blue - drove up a hill OK and down the other side, up the next hill and I thought I had suddenly encountered a very strong headwind the car struggled so much. Don't know if this has any bearing on the diagnosis.
Skip, never heard any popping from the intake, but engine temps start heading north after extended work, but I put that down to the fact that the engine is misfiring and having to work harder. I haven't seen Seafoam carby cleaner here in Oz, but now that I know about it, I will see if I can source it from somewhere. I will also be checking the timing (hopefully this weekend).
NorthWet - I agree with you and I am going to be replacing pretty much everything in the ignition first. Just clicked over the 400,000km mark, so components may be a little worn. I am waiting for a set of leads to be delivered, along with a new rotor button. I am also thining I will replace the ignition coil - I have been told that an ignition coil either works or it doesn't , no in between, but I suppose it can't hurt (and the workshop manual also suggests this as a possible remedy). What do you think?
85Sub4WD - I will also do as you suggest. I did find the vacuum advance line was disconnected, but I think I did that when I was changing the plugs. I will however check what I can.
I really appreciate the responses so far. I'll keep you up to date on the outcomes.
