I've got a 20v 4age in my Striker. It was running perfectly over the weekend driving along a main road until i slowed to a roundabout when it started running roughly. It sounds a bit like a Subaru and is running like it at all revs the whole time now.

I thought it was a misfire and have been trying to find the problem accordingly. Initially when I unplugged 3 there was no change and when i unplugged any of the others it stuttered. Now when i unplug 4 there is no change either, but when 1 and 2 are unplugged it still stutters. Does this sound like a misfire problem? Could it be a mapping problem? Is there a diagnostic tool for omex ecus?

I have tried:

some other plugs from an old engine - no change
swapped the leads from 1 and 2 onto 3 and 4 - no change
tried another coil pack - no change
checked the compressions - all as per the engine manual
checked the timing wheel sensor is not loose or moved
running the engine with the air filters off
i opened the fuel tank but there didn't seem to be a vacuum

anyone got any ideas/help this is driving me mad!?

Check the inlet manifold for an air leak either at the gasket or a vac' hose. Thats only thing that springs to mind given you've covered most bases. A rubber hose pushed onto the end of a blow torch with the burner nozzel removed is good for finding a leak. Less messy than WD40 or similar. Just move the pipe around the manifold and you'll hear the revs pick up when you're near a leak.

couple of others that spring to ming

1 has wirring moved ? trigger wheel sensor wire picking up interferance ( is it sheilded )
2 bad earth on ECU.

Injection or carbs? If injection are number 3 and 4 injectors operating?

Thanks for the ideas and help! Going to try them over the weekend.

Its injectors, i switched 3 and 4 early on in the problem solving but i will try switching them with 1 and 2.

The earth on the ecu is something i considered as i've had some trouble with interference from the indicators effecting the speedo and rev counter on the same journey but i wasnt really sure how to test the earths. I tried to wire directly from an earth point to the battery but couldnt tell if it made any difference.

Ok so it was a leak in the inlet manifold gasket. It now runs like normal!

I don't like to say it but... I'm good!

It's easier when you've given a good description and already covered most bases though.