All of a sudden my TH is missing really really badly., to the extent it will hardly accelarate. Its gas/petrol and is probably a little worse on gas. So that illimunate any fuel issues?

I pulled the front 3 plugs but they seem ok and the back are 3 iridiums about 30ks old. It seems a little worse than just one cyclinder i think.

Any thoughts?

Maybe just take them out and give them a clean! happened to my commodore last the other day and made a massive different, maybe the back ones are old? did you change them yourself? maybe they havent been changed !

Yea back ones are iridium and i changed them all about 30,000 ks ago, will check them though

Its that bad i can hardly accelerate. And on gas its useless.

Id try plugs first maybe while all that craps off clean intake/throttle body

Has it backfired lately?? Do you have an airleak after the maf? As in its sucking sensed air?

How old are the leads? All plugged into the dissy cap ok?

From other cases reported, this sounds to me more like failure of one or more spark plug leads or the ignition coil.

When this happened to mine, turned out to be the coil. Good luck

I'' try the back 3 plugs but seems more than one cylinder breaking down. Might be the coil..

It could be a coil but lets go a bit basic first.

You don't just replace leads. Not unless you're cashed up.
Measure the resistance of the HT leads first.
Generally you're looking at around 6k ohms.
But it may not be the leads.

It could be fuel starvation or bad ign timing.
Have you looked at the colour of the fuel in the inlet side of the fuel filter?
The filter may have blocked up.
A bad connection in the wiring loom or the plug to the dizzy may be the prob.

Verendah

I thought fuel filter as i've encountered this before , but it does it on gas as well. probably worse on gas than petrol. Anything under load and it misses badly

Typical of a weak spark. Could be leads, could be distributor cap central carbon contact, could be rotor arm, could be weak coil.

Why not grab a distributor complete with cap and leads from a wrecker? (look for a car with the intake already off, if you are lucky.)

Yeah will check dissy cap and rotor tonight. hopefully its just that

Dissy cap was stuffed but still has the problem. Took the manifold and plugs look good, might try the resistance of the leads next.

And the winner is COIL, all running fine again!!!

And the winner is COIL, all running fine again!!!

Well done! I have a new coil sitting around for the day one of my 2 Magnas does the same. lol