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[johnnyutah]

If anybody can offer any suggestions to the following problem I'd be grateful as I'm stumped at the moment.

 

The wife's mini is a 1990 998cc.

It was running fine up until the other day when it started on what sounded like two cylinders and was backfiring away merrily!

 

So far I've rechecked the valve clearances and they were fine.  I've changed the plugs, points and condenser to ones I know worked (the ones I took out at the last service in May).  The HT leads are only a couple of years old, but I've swapped them for the old ones. 

 

I've serviced the carb, fuel is coming through OK.

 

I've done a compression test.  All four cylinders were reading 180.

 

I've changed the distributor cap and rotor arm.

 

For a very brief 15 minute period yesterday I did eventually get it running like a dream.  I'd just finished fine tuning the timing with the timing light and was just adjusting the idle speed then it cut out.

 

It then struggled to start, but the engine was very hot so I let it cool down and went for a brew.

When I came back to try and start it again I'm back to square one.  It will start now, but it's terribly lumpy and only seems to be running on two cylinders.  It doesn't seem to make any difference when you pull the HT lead of 2 & 3 cylinders.

 

I've held a spare plug against the block and connected each HT lead in turn and they all give a strong spark.

 

I really don't know what to do next.

 

Any ideas?

[Alex_B]

I had this issue, my problem turned out to be one of the wires from the electronic igniton module grounding out on the dizzy shaft, it had worn through and the engine only occasionally was running on all 4 and when it was it was running beautifully. 

so checking the ignition system and check for any shorts, checking points and condenser if you dont have electronic igniton.