cylinder misfire

[yxd0018]

I had twice cylinder 5 misfire. After researching in the forum, I replaced all ignition coils of E36 98'. Within a week, I get cylinder 6 misfire. Is that new coil 6 bad? What should I do? Thanks.

[Eric93se]

Sadly on your to-do list is a compression test.

You could run a couple bottles of injector cleaner. Get Royal purple brand.

[zellamay]

So it probably had nothing to do with coils, but here's what I'd do next because it's easy and free: switch coils among cylinders. If the misfire follows the coil, then the coil is bad.

[yxd0018]

I switched coil 6 to 3, then 2 days ago I get coil 5 misfire. Any idea?

[spyderg0d]

If you got all new coils, its probably not one of those... Did you put in new spark plugs?
Does the car eat coolant or any other codes besides the cylinder misfire?
Have you checked the crank and cam sensors?

[yxd0018]

I've replaced all spark plugs (BKR6EQUP NGK 3199) in Dec 2018. I replaced radiator, all intake manifold gaskets and leaking coolant hose behind manifold, Camshaft Position Sensor (VDO 12141703221), water pump in 2019 before misfire happened. I have not checked crank sensor. What should I look for?
Sometimes misfire error came up alone, sometimes it came with error code 1421 which was popping before from time to time even in summer. 2nd air pump is working and there is no leak in the hose. So I don't know what's going on.

Regarding coil, it's the original and the car is 200k now. Should i replace them anyway for insurance or I need to put my old coils back? Heard they should be replaced 150k+ onwards.

[yxd0018]

any idea?

[XnWarden]

What do the tips of the plugs look like

Sent from my SM-G975U using Tapatalk

[yxd0018]

What do the tips of the plugs look like

Sent from my SM-G975U using Tapatalk

When I replaced the plugs or now?
When I replaced them, it's not bad, not dark, not worn out.