2017 Audi A3 Which SparkPlug is which


Greetings. Have a 2017 Audi A3 Quattro 2.0l US version. It started throwing a P0303 code. Replaced all four plugs but problem persists. Was going to replace ignition coil next but not sure which one is for the third cylinder. All four are lined up in a row left to right wheel to wheel (as opposed to front to back) how do I know which is number 3?


Is it transverse motor? Or longitudinal layout?

Yeah it does, so I’m fairly sure it’s the coil, but it just confirms the order is either 1234 from facing the front or it’s 4321 from facing the front. Was hoping to avoid moving the outter ones to the inner ones in order to confirm.

The cylinders are numbered from the serpentine belt side back to the transmission. Swap coils between 2 and 3… the middle 2 cylinders. If the misfire sets a P0302 code… you know the coil is bad. If the misfire stays as a P0303, there is a problem with cglinder 3… So time for a compression test.

If the #3 plug was wet with oil, it is not likely to be an ignition problem.

As @Mustangman said. Things get more complicated with V engines, some number them based on which is closer to the ‘front’ (serpentine belt), so alternating between banks, some number them 123 on one bank, then 456 on the other.


Thank you— this was helpful. The simple answer of closest to serp belt is #1 was what I was looking for confirmation on. Obviously I could swap and swap and swap and eventually figure it out but one would think there’s some diagram or ref doc listed somewhere so people don’t have to go through that.
Anyway, after pulling and replacing the coil plug, the problem indeed went away. (Btw the plugs were fine. Normal carbon buildup as expected but no oil or other fluids.)


I agree it would be a good idea for manufacturer to show the plug number order on the emissions-maintenance sticker on the under-side of the hood. I expect they don’t b/c they’re thinking the typical Audi car owner isn’t going to be repairing their own car, will take it to a dealership instead, and that the dealership shop will already know. The car’s shop manual would have that sort of information. You might be able to get short-term access to an electronic version using the Audi website for a small fee. Googling "2017 audi a3 repair manual " might turn up a used paper copy.

I had to figure this out on my Ford truck’s v8 engine one time. Turns out Ford started at the front of the engine and went to the rear, 1-4 on one side, then 5-8 the other. Still leaves the question of which is 1 and which is 5? Right side, or left side? If you think about it, on V8 configurations where there’s only one crankshaft to share with each side of the V, one of the two pretty much has to be more toward the front than the other… On my truck the one most toward the front is number 1.

George, if you look carefully at your truck’s engine you’ll see that one of the cylinder heads is an inch or so farther forward than the other. That’s the offset of the connecting rods on the crankshaft. The passenger side front cylinder is the frontmost on the crank, the driver’s side front rod is right behind it. That’s why on your Ford of that era number one is passenger side front.
Ford numbered the cylinder 1,2,3 and 4 on the same side, then 5 at the driver’s side front, followed of course by 6,7 and 8.

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Ford seems to have the lead cylinder on the passenger side while GM’s lead is on the drivers side. Just because!

Do manufacturers still have the firing order on the intake manifold? My older GM’s did. I haven’t had a GM in over 30 years now.

It’s on my Ford truck’s intake manifold. Haven’ noticed anything like that on the Corolla intake manifold though.