1.2 tsi petrol with 72k kms

misfiring only under load, when exalerating, particularly in raining, wet conditions.

It skips on firing one cylinder at irregular intervals.

Started about 1000kms ago with rare, single miss and has recently increased. ie the gaps between misfires get shorter, now it's stuttering under load.

 

I'm thinking of looking at:

Distributor brushes (are they visible?)

Distributor leads (can I check them with a cheap multimeter?)

Sparkplugs, obviously, but not keen on swapping out just for kicks.

 

Any pointers are most welcome, thank you,

 

Harro

One of the plug leads is notorious for failing on this engine, no3?

As kenfowler says.  Most likely to be Insulation breakdown of one of the plug leads, allowing arcing to grounded metal.  Firing voltage rises under load (acceleration) which makes breakdown more likely.  You can't test with a normal multi meter.  Newer replacement leads were modified with an extra insulation sleeve to keep them away from heat.  I suggest you get a set of four new silicone insulated leads which withstand high temperatures better.

Spark plugs are due to be changed every 40,000 miles / 64,000 km so check if they have been done.  Worn spark plugs have a bigger gap which will increase the firing voltage and also make breakdown more likely.

Thank you Ken & Austin for taking your time,sharing your knowledge with me.

On 23/01/2020 at 08:03, freundeskreis said:

 

Distributor brushes (are they visible?)

Distributor leads (can I check them with a cheap multimeter?)

 

 

If it's the EA111 8v tsi 1.2 (oil filter above alternator) ,which I think it is, then as already mentioned above ignition/plug lead 3 can fail and also the wasted spark coil pack is a know fail item (This is possibly what you think is the distributor, it's actually a twin coil pack with each one connected to two cylinders via iginition leads).

 

The coil pack is cheap and a very easy to fit.

 

Edited 27 January, 20206 yr by bigjohn

Something to look out for on ours... do we know if there was a manufacturing date that they fixed this issue from? Ours is a very late '63 plate EA111 1.2

My 2013 Yeti 1.2 had No.3 plug lead failure which seemed to cause arcing at the connection with the ignition coil pack on top of the engine.  Need to take photos of position of leads before removing them. Quite simple job but ensure leads routed AWAY from the hot metat shields around plugs. I've got more photos if you need them.