The symptoms are a misfire over 4000rpm. The severity of the misfire varies from slight to major. Very occasionally it runs without a misfire - like this morning when I took it out for a 10 minute test run. It ran great and was flying along. I then took it out couple of hours later and it started to misfire. Took it out a couple of hours after that and it would hardly go at all to the point where it couldn't even idle without me blipping the throttle to keep it going.
The issue has been going on for at least a year now and i haven't been able to really drive it because of the issue.
these are things I've done to try and rectify it :
Changed the entire ignition system.
Checked timing
checked the valve clearances
Checked fuel flow and pressure
Cleaned the carbs
Replaced the fuel pump / fuel filter
Swapped the fuel pump relay
Carried out a compression test
I think that's it but there's probably more
Can anyone one give me some hope and explain what could cause a car to go from running great to running terribly like this? The hillclimbing season isn't far away now and I'm beginning to think I'm going to miss another season because of this
![Sad :(](./images/smilies/icon_sad.gif)