2012 Holden Barina running rough.

F16D4 engine 1.6l engine. Came in to our workshop on a tow truck it was so bad.
I got fault code P0301 "cylinder 1 misfire detected".
I pulled out the spark plugs - cylinder 2 was 2 inches deep in oil - though that never seems to cause a misfire?
I cleaned out the oil, swapped the plugs around, and reassembled it and started it up again.
I couldn't bench test the coil because it has 7 pins and we don't have a pinout for the tester for 7 pins.
The engine ran smooth for a few minutes, then started getting rough.
From what I've learned here I went to fuel trims. There are a few other pictures below, one showing long term fuel trims
of -13% but this is the one that shows when the engine is running rough. The oscillations in the centre of the image are when it
is running smoothly, either side you can see the rough pattern where the fuel trims are trying to get the O2 sensor to respond.
The question is whether the O2 sensor is sticking (would it be more 'permanent'?) or something is actually causing a rich condition.

One of the guys just mentioned to me that we had one of these engines before and they are prone to carbon buildup on the valves
which causes the rough running. I think I need to connect my new vacuum gauge!

I tried connecting my vacuum gauge but it wasn't easy so I scoped map sensor which should show the same as
a vacuum gauge I would think?
The first half of the picture is with the engine running well, then the second half it starts running rough and the map sensor
reading goes all over the place which I would imagine suggests a sticking valve(??)

Hey Paul! I'm unfamiliar with this engine, so I'm struggling a bit to come up with suggestions. :blush: The valve cover and coil pack looks similar to some of the Suzuki/GM engines we see in the States? I'll have to ask Wikipedia.

That first picture you posted is throwing me off. :silly: Ignition and fuel misfires will drive the O2 lean, so neither of those account for the O2 sticking rich at times. If you wanted to prove or disprove an O2 problem, you could try disconnecting it and force Open Loop. If the rough running goes away, you can figure you have some kind of fuel control problem.

Though, TBH, I think the issue you're seeing is caused by something else. The MAP sensor is good, but it likely won't be quite as sensitive as your vacuum gauge. If you can find a way to rig the gauge in, that'd be the way to go.

Any misfire counters? If you can watch which cylinder counts up when the roughness happens, you'll at least have a direction to go in. If you really suspect some kind of mechanical issue, you can try doing a running compression test on the suspect cylinder.

Thanks Tyler I use the name "Paul6004" to log in at work - Paul is the owner I'm at home now - apparently this engine has a lot of trouble with carbon build up and usually throws a P0300 for random misfire - most people replace the coil first.
This particular one though specifies cylinder 1. I don't have a coil-probe thingy to scope the coils (they are all joined together so not sure how effective it would be) so I scoped the voltage to the coil pack and the voltage drop when each switched was equal. I ordered another coil pack which I got at 1/3 the price online and fitted it today and it didn't work at all so I ended up fitting the old one again to drive it back out of the workshop. I'm busy ordering another new coil pack

Tyler wrote: you can try doing a running compression test on the suspect cylinder.

I had never heard of that before - interesting. It will be difficult with this coil pack though

With regard to this image - the map sensor shows a drop in vacuum for a while THEN the O2 sensor goes rich for a while.
Could that perhaps be the ECU responding to the misfire when those O2 sensor voltages drop below the line during the misfire?

Desmond6004 wrote: I'm busy ordering another new coil pack

You can still test the spark output of the existing coil, if you want! Just remove it from the head, plug it in and point the boots upward. Unplug the injectors, then have someone crank the engine while you check each coil tower with a test light. If there's a dead or weak tower, you'll know it fairly quickly. Because you've got a P0301, you can compare the spark out of that tower to the others.

It will be difficult with this coil pack though

Yeah I hate this coil design. If possible, you can remove the coil boot for #1 and sneak the compression hose in past the coil.

Tyler wrote: You can still test the spark output of the existing coil, if you want! Just remove it from the head, plug it in and point the boots upward..

It generally only starts misfiring after it's warmed up a bit so could involve quite a bit of cranking to get the fault.

Another coil fixed the problem.