Multiple cylinder misfire on 2006 1.4 BBZ engine

[warp_speed]

Looking for some advice. I've got a SEAT Ibiza (56 reg) 1.4 with BBZ engine and its recently came up with the engine management light flashing. Plugged in the VCDS and it came up with multiple cylinder misfire detected with fault codes for cylinder 1, 3 and 4. I've changed the coil pack on cylinder 3 to see if it would help the situation but no change, group 14 and 15 shows multiple counts of misfire across all 3 cylinders. Any other ideas what this could be.

[Sam]

The ignition leads run in the grove of the engine cover which often causes them to deteriorate - Edit: I may be talking crap here, I might be thinking of the Polo 1.4 MPI not the BBZ in the 1.4 16v Ibiza (I have both vehicles!). The next part will work regardless though, it'll hopefully eliminate the leads being an issue.

Making a note of which lead goes where, remove the lead from #2 and swap it with one that you know is misfiring.

See if the misfire moves.

[warp_speed]

The ignition leads run in the grove of the engine cover which often causes them to deteriorate - Edit: I may be talking crap here, I might be thinking of the Polo 1.4 MPI not the BBZ in the 1.4 16v Ibiza (I have both vehicles!). The next part will work regardless though, it'll hopefully eliminate the leads being an issue.

Making a note of which lead goes where, remove the lead from #2 and swap it with one that you know is misfiring.

See if the misfire moves.

It has coil packs, no HT leads. But have checked the wiring to the coil packs and they look ok.

[Sam]

I'm confusing my vehicles, apologies.

You say you changed the coilpack on #3 but not the others. For the sake of £30 it might be worth changing all 4.

When was it last serviced, how old are the plugs and finally what were the exact codes stored?

[zollaf]

i would try some new sparkplugs as well.

[Rob69]

Compression test maybe worth doing if no joy with plugs and packs.

[warp_speed]

Compression test maybe worth doing if no joy with plugs and packs.

Next on my list of things to do, any idea on what the compression value should be?

[zollaf]

a petrol should be around 150 - 180 ish, but what you want are even compressions across all 4. if one or more are 20 psi out, then you have found a potential problem.

[warp_speed]

I'm confusing my vehicles, apologies.

You say you changed the coilpack on #3 but not the others. For the sake of £30 it might be worth changing all 4.

When was it last serviced, how old are the plugs and finally what were the exact codes stored?

Serviced around 5 months ago. Plugs changed around 20k and I used a standard handheld scanner (VCDS laptop not available at the time) and it reported misfire on cylinder 3, hence got a coil pack for it (£43 at TPS). Got home and connecting up VCDS it reported the following fault codes.

P0300 16684
P0303 16687
P0304 16688

I checked out group 14 and 15 of VCDS and it showed multiple misfire counts across cylinders 1, 3 and 4, nothing for 2.

[zollaf]

20k on a set of plugs, change them..