Snapple said:

Hi, I'm a new member so hoping I've got this posting thing right! At my wits end in trying to sort son's car - so far, I think I've established: timing belt has not slipped; HT leads ok; coil pack replaced; cylinder head ok. Could ECU have failed and, if so, what is involved - I sense it's not particularly straight forward matter! I'd really appreciate any advice/guidance on the matter. Thank you. Neil

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Do a compression test wet & dry, see how the cylinder compressions look before jumping to ECU conclusion.

I know these bravos get a lot of problems with injectors. Maybe you should get them tested?

Thanks for responses gents, I'll look into your suggestions - Perhaps it would be worth getting fault codes read?

Tried new plugs, or simple as swapping plugs to see if problems moves with plugs, not sure if injectors are swapable, I seem to think they are, so you could also try after the plug swap try an injector swap to again see if problem moves with parts, just a few simple cheap tries to see if you can narrow down problem, what colour is your oil, black or creamy, loosing any water from cooling system? these are good indicators of head gasket.
Are the plugs wet when you take em out, if they are then it is fueling ok no blocks in fuel line to these two cyinders.
All you really have to look at I supose is
Plugs - Sparking?
Injectors - Working ok?
Cylinder Presure - Head Leak?
You said Cylinder head is ok what gave you that idea? have you had a test done? it is not very often you get two cylinders next to each other not working usually indicates a breach of compresion across the two, I am guessing the leads from the new coil where put back in right order, seems a silly question but easily done, also how did you get to ECU problem or was that an outside guess just in case, has the car thrown any other problems up leading to this problem to indicate ECU, Getting ECU read is a good start, but the plug change is a free alternative as is the injector swap save you some cash 1st.......

Welcome to the forum snappel,
Plugs 3 and 4 use seperate coil windings on that coil pack so its not likely the pack. As Foxy says I would do a compression test, especialy because the missfiring cylinders are next to each other. The compression testers are cheap and the results will give you an idea if its gasket or timing.

When doing the compression test look at the gausge as its pumping up, looking for a double puff.

Cheers

SPD