Just changed the spark plugs on my 1.2 TSI because it was having a mild cough at low RPM and thought maybe it would help. 

 

However after swapping, the idle is now much rougher. When I rev up to 2k and hold it there, it goes smoother but when it falls back to idle, after 10-20 second it goes very rough again. Any ideas what might be causing this? Haven't dared to take it for a spin yet.

 

I've also attached a picture of the plugs that came out, don't seem to be in bad order. 

 

Edit: just undone all the plugs again and it seems to be number 3 as it was oily coming out. The old number 3 was oily as well. Should I consider changing the coil pack? How come after changing the plugs it has gone worse? 

Edited 17 July, 20196 yr by Renks

Did the Spark Plugs come from a trusted supplier?

Were all 4 checked for the correct gap before going in, and what was / is that gap?

 

No damage to the Ignition Coils?

 

Pipework / breathers / air intake sealed OK?

11 minutes ago, Roottootemoot said:

Did the Spark Plugs come from a trusted supplier?

Were all 4 checked for the correct gap before going in, and what was / is that gap?

 

No damage to the Ignition Coils?

 

Pipework / breathers / air intake sealed OK?

Plugs are NGK from Opie Oils suggested by another user on this forum so I would assume that would be trusted. However I do not own the gauges to check the gap.

 

There doesn't seem to be any damage visually to the ignition coils. Pipework seems fine, and I would assume if it was a leak of sorts then misfire would be constant, but its intermittent. 

 

I fiddled with the wire for third cylinder coming from ignition pack to coil (twisting the connections on both ends) and after having checked all the plugs again, seems that misfire has almost gone, but a singular one every now and then. Also seems that it was number 3 before changing the plugs and after, that is misfiring as it is the only oily one.

Do a search on the lead 3 upgrade, or maybe @xman will be along and help,

i cant search right now.  plenty threads on it but i only know about 1.2TSI's what i have read on here.

1 minute ago, Roottootemoot said:

Do a search on the lead 3 upgrade, or maybe @xman will be along and help,

 i cant search right now.  plenty threads on it but i only know about 1.2TSI's what i have read on here.

 

I will do some search, thank you very much for your input!

Update on what's happened:

 

After I got it running decently smoothly on idle again, I took it around for a spin, and then realised that as I'm trying to accelerate, it misfires bad. Sure enough it was cylinder 3 again, but I noticed that the ceramic has distinct burn cracks in it. So I swapped it out for an older plug from cylinder 2 and same essentially.

Swap it out again, idle is essentially misfire free but as I get to higher gears it starts to misfire when I try to accelerate (especially with 4th and 5th gear, low RPM, slight uphill and try to accelerate). After some driving, seems like it starts to do even with 3rd and 2nd with lower loads. 

 

Going to TPS tomorrow to see if they have ignition wires/coils, as I suspect that to be the cause. Any ideas if I'm right or wrong would be appreciated? 

How did you remove the leads? You need to use a tool (Sealey VS5293) to pull the metal boots off, if you pulled by the leads, its probable you will have broken the lead.

 

If your car has the old plain leads without the corrugated trunking then its very likely that No.3 is duff anyway and has been for a long time. You can check with a  multimeter that the lead has gone open circuit.

Recommended to change the set. About £43 for an OE set 

NGK-44316-44316-Ignition-Cable-Set

 

 

If after changing leads its still misfiring then the damaged leads, further disturbed have probably taken down the coilpak. The early ones were prone to fail when no.3 lead went. Fortunately the coil pack is quite cheap and easy to change. Available from around £25 iirc at many outlets.

I used the tool you mention to pull from the metal sleeve, I did not pull from the leads themselves. 

 

The leads I have, have the same metal sleeving around the connector to the plug so I'm assuming it's not just the plain wire you mention?

 

Thank you for your assurance about the issue and the thoughts I had about it. 

I will start from the leads and if it doesn't fix it then will change the pack as well. Have quite important things coming up very soon and need the car to be up and running asap 😀. 

Update: Swapped the ignition leads and is running smoothly again, many thanks for helping me out @xman and @Roottootemoot in my stressful situation.