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Hi,

I have an issue with my car intermittently misfiring whilst driving. I plugged a computer in and it said an issue with the coil in cylinder 3. Changed the coil - the symptoms exactly the same. Several weeks later, I swapped out the genuine VW spark plug in cylinder 3 (that had been in 6 months) for an old one (factory fitted one) and symptoms did not happen for 4 weeks. After 4 weeks of no misfiring, purchased a new VW spark plug and put this in cylinder 3 and symptoms started immediately again (intermittently) …

Seems quite bizzare. Anyone seen anything like this before?

Thanks in advance.

did you use the correct plugs? gaps ok? clean the spark plug hole? use proper grease below the coil? what does the misfiring plug look like?

Could be injector too.

Thanks for replying. It was definitely the correct spark plug from VW. The gap looks fine. The spark plug I took out (if it was failing) looked pristine. Am I supposed to use grease in the coil connector?

Also what do you mean about the spark plug hole? The one in the engine block? Thanks in advance

Richard54321a wrote: Thu Oct 05, 2023 8:57 pm Thanks for replying. It was definitely the correct spark plug from VW. The gap looks fine. The spark plug I took out (if it was failing) looked pristine. Am I supposed to use grease in the coil connector?

I don't think that VW Group ever recommended applying silicone paste to the end of the coils on that engine, the main purpose of the silicone paste, I think, is to minimise the possibility of the "contact tube" which is a replaceable item on some of the newer/later coils, gripped/seizing to the insulator and so ending up separating from the coil and being left stuck to the plug down the deep hole in the cylinder head - and so creating a problem for some people.

What engine is this?

It’s a POLO S 60, petrol, 2012, 3 cylinder, 1198cc

If you swap around coils and/or plugs, does the problem move along with that?

Good idea. I guess if it follows the coil or the plug it points to either the coil or the plug … if it doesn’t what else could it be?

Thanks in advance

If not that maybe an injector - or the normal wear in the valve guide, so you might need to swop injectors.

Edit:- or another option, it is a wiring fault that you make or break while changing plugs over?

Thanks for your reply. Maybe it could be a wiring fault - but with the old plug in it works fine - no fault.

The computer error code is P0353.

I can only speak from the 4-cylinder 1.2 16V, but I guess should be similar in a way.
The wiring around coil 4 connector is quite a tight fit on my car. It rubs up against the valve cover and PCV tube. Over time that could possibly become brittle and cause electrical issues.
It could just be that when you swap the plug you're actually wiggling wiring into place again.

I actually have a link somewhere to someone with a 1.4TSI Jetta that rerouted that cylinder's wiring when doing some heat shielding in order to prevent any wear on those wires.

But do the coil swap trick to see if the misfire moves to another cylinder. That will indicate it is coil. If it remains in the same cylinder then it's wiring, injector or some other mechanical fault.

Thanks for all of your help! Makes a lot of sense! Going to try some of those things thanks! Then I’ll repost to say if it worked or not! Thanks again.

Ps: also if it was an injector you wouldn’t think it would have resolved with the old spark plug. Thanks

Richard54321a wrote: Sat Oct 07, 2023 8:32 am snip --- snip
Ps: also if it was an injector you wouldn’t think it would have resolved with the old spark plug. Thanks

Correct, but - never discount anything, try the easy things first(obviously).

Good Luck!