Pinto 1.8 SOHC.

I'm getting a good spark on all 4 plugs but for some reason cylinder number 4 doesn't seem to be Firing any more than about 5% of the time as estimated by the low increase in exhaust temperature.

I'm currently unable to let the engine idle so I can't effectively adjust the timing, though the facts that cylinders 1, 2 and 3 are nice and hot suggets to me that I must be doing something right.

I've done all the usual stuff of swapping HT leads and plugs but the same symptoms remain.

Not sure if this is reelant but at this time I haven't attached my throttle or manual choke cable to the carb so I'm only able to keep the enginie firing by manually operating the throttle / choke. The carb is the orignal that came with the donor which I test drove before buying so I know it can work.

Any suggestions?

check for tight tappets when engine is cold also test for air leaks using wd40 sprayed around inlet manifold to cylinder head joint, engine revs will increase if wd40 is sprayed into area of air leak,also try changing distributor cap. hope this helps , rusty nuts

maybe a compression check?

I've not tried this yet but I've just noticed that the brake servo take off from the inlet manifold is wide open, it also just happens to be on cylinder 4.

I'll blank this off and see how this changes things.

let us know how you get on if possible cos my servo is gone, need to come up with a plan for the vacuum pipe!

I managed to plug the hole in the manifold with a very large bolt that came off the Sierra donor's suspension.

The result is that the engine now runs very smoothly, particularly so when its come off the choke.

Now all I need to do is find out what the thread is on this bolt and go to my local hardware shop.

At first I thought I'd solved the problem with a 10mm compression stop end from the plumbers merchant, however, this is not quite the same thread. I suspect it's going to be something obscure such as 1/2 inch BSP or something.

Anyone know what the thread on the manifold is likely to be?

Russell