Hello all

Im having running problems with my 1989 2wd sapphire Cosworth

When I tried to start it the other day she sounded like it was only firing on 2 cylinders. A quick check and nothing obvious . So I took all the spark plugs out and gave them a clean and still no joy, I then decided to check in the following order.
And trying to start the car in between each check with no difference.

Changed all spark plugs one by one

Changed the ht leads one by one.

Changed dizzy cap and rotor arm

Checked for spark on each plug

Checked the coil

Checked the timing

Checked petrol was going in to the cylinders

Checked for all connections on the battery

Checked the crank sensor and cleaned it and all 4 trigger points.

Checked compression ( 8.5 bar) so all good

Generally checked all wire to sensors ect.

By-passed the alarm / immobiliser.


Now im no expert mechanic but to my thinking with all these parts either checked or replaced, I have no idea what else it could be as on the Saturday it ran like a dreams and from Monday its dead with no in-between stage of running like a bag of sh**.
The one thing I think it could be is the spark amplifier but not sure how to test it on a cos.
Can someone tell me how to check it with a meter or give me anything else to check as its too cold to be fighiting with it for hours over the weekend.

All help would be greatly received

Its on a stage 3 spec if that makes any difference which I cant see.

Thanks in advanced peeps