Major misfire

[Bigant]

Hi all

Finally got the series 2a back on the road with a full MOT, first trip out the engine starts to misfire pretty badly, mange to get home, I was only down the road and after initial examination I can't find the problems.

I have checked the spark plug gaps, the gap on the points and all is good. I have removed the HT leads from each plug with the engine running and interestingly the misfire only gets worse when one particular lead is removed.

The question is therefore what could cause this misfire issue having had the engine running and ticking over nicely prior to the MOT?

Any help would be much appreciated.

Cheers

Bigant

[secondjeremy]

What's the compression like when you turn it over on the starting handle?

Is the rotor arm sound? Is the distributor cap DRY and clean inside?

Are the plug insulators dry?

Are the points gaps the same for all 4 cam lobes?

What happens when you pull the distributor base plate lead - and the lead from the points to the distributor side contact?

Are the strange insulators for the points on the distributor post in place correctly and not squashed?

Is the inlet manifold - engine and carburettor joints tight?

[Bushpig110]

Check compression on the cylinders, possible head gasket or burnt out valve ?

If the misfire is worse on one cylinder swap the plugs and leads around one at a time to see if the misfire moves if it does you have a faulty lead or plug if it stays the same fault will be in the dissy, or engine.

Change the condenser they give unusual running faults that get worse when it's all hot or been running a while and then perfect again the next morning when it's cold

[NL_Lexxie]

Hi,

I have had the same with my S3 2.5L petrol, it was the coil giving problems when warm.

If you have a spare coil I would test if that solves your problem.