Hi Henrik..with the firing on three cylinders issue i replaced all leads rotor dizzy plugs..did not help..the faulty cylinder would be dead on initial start up and then after a minute or so (sometimes longer) would cut in and out until it fired up as normal and would be fine for the rest of the day only to re appear the following morning..The symptons felt electrical in behaviour.The exhaust manifold on non firing cylinder was cooler towards the other outlets.After many hours of pulling plugs and rechecking i was stumped.Then i started looking towards the carb as a possible .I was very reluctant to take it apart without being sure it was the issue.In the end i put a fuel treatment in the tank and ran the car whilst using carb cleaner into the venturi..(yours is injection?).This vastly improved my issue and although not perfect fires on all four now even through this cold snap.I know the carb needs rebuilding in time..its a long shot but would rule out the fuel system.Perhaps the inlet manifold gasket?.I hope you get it sorted hj.

Hi,

Thanks for that.

I over-hauled the fuel system and fitted new valve-springs and valve stem seals 18 months ago, but I will go over things this weekend. It feel ignition-y rather than fuel. I had a thermo-gun on the exhaust runners previously, but will do it again this weekend. The one my timing showed as dead was cold.

Inlet manifold gasket... I think that would be a constant problem, not that kind of specific surging. But I will get my vacuum gauge on the manifold this weekend and see if it is steady.

I have checked compression every couple of years for twenty years, never dropped. I may do it again this weekend, if my fingers haven't frozen off.

Henrik

Good afternoon,

I really dug into checking everything today, and won't bore you with details, but it looks like it's a bad spark plug. It's not broken, just erratic, is that really possible?

I have some almost new Volvo spark plugs lying around, but they don't fit the HT leads as the top cap can't be removed. I will either buy a spare plug or grind the top of the Volvo plug to get it to fit.

Regards,
Henrik

A duff/fake ,new, NGK plug drove me nuts for twelve months.

Spent half an hour filing down the mushroom end on my almost-new genuine Volvo spark plug I had lying in the garage (don't know why there has to be two different kind of HT leads), and it purrs like a kitten now.

Thanks
Henrik

Good morning,

I think I have narrowed this problem down to being a leaking cold-start injector.

Does anyone know where I can get a new one? All my usual dealers say they are discontinued.

Regards,
Henrik Morsing

After many months of investigations, this turned out to be #2 injector leaking.

The upside to this story is that replacing injectors, grinding the valves and draining 50ml of oil out of the timing advance canister has gained more than 20% in fuel economy! (Probably mostly because of the new injectors).

Also removed the flame-trap, which I wrongly remembered doing in 2005, which means the engine and transmissions are no longer drenched in oil.

I reached over 300 miles before the fuel gauge hit red on my first full tank since fixing all this.

Regards,
Henrik Morsing