Popping From Exhaust At Hot Idle

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Hi all,

First posting here to ask for some help.

My wife's Ford KA has begun a little annoying issue. It's a 1.3i 2000, MK1.

Only 58,000 miles on it.

Last couple of months it began popping from the exhuast intermittently at hot idle. Sounds like unburnt fuel coming out.

I have just put a new coil in and HT leads. Plugs were changed about 3 months ago. Just pulled them today. As clean as a whistle, no soot or oil whatsover. Gap was only about 0.75mm though. Could a small gap be causin an issue? 1-1.1mm I heard they should be set at.

I checked the valve clearances and they were very tight. I'm thinking
the worst that someone has overtightened these and burnt an exhaust
valve.

I have adjusted them to 0.5mm/0.2mm as indicated but still popping.

Any tips about adjusting them correctly?

I have cleaned out the ICV also. Maybe I should clean out the main body also that attaches the ICV to the throttle body.

No loss of power, drives fine when pulling away. Just noticeable at idle.

Hope someone can tune in and offer some advice. It has its MOT next
month! Don't want any nasty surprises as I've just been busy with all
the paintwork and its going to need new tyres.

What I did notice on the old HT leads about 2-3 inches from the coil was a bit of black soot on them.

Where would this have come from as at the back you have the inlet
manifold? The exhaust manifold is at the front. This confused me
somewhat.

Many thanks

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Don't want to speak too soon but I may have improved it.

I gapped all plugs to 1.0mm. I did notice one plugs electrode a tad shorter than the others. Might get that replaced.

I checked all clearances again. Adjusted 2 inlet valves a fraction wider.

Started her up and let it warm up until the engine was relatively hot.

No popping!! Now I need to give it a good run to get it hotter
another day. I flapped a bit of paper on the tail pipe and was not
sucked in.

I attached a bit of paper on a stick and waved it about around areas
of the exhaust. Not sure if I found a very small leak at the end of the
flex cat converter bit or may have just been the wind blowing about on the driveway.

It was idling better, slower and smoother, than yesterday after regapping the plugs. I
thought these NGK were meant to come gapped to 1mm from factory. They
were less than 0.75mm!

Lets just hope it was just the gapping.

Keep you updated.