Do a compression test on all cylinders and compare findings. All cylinders should be within 10% of each other.
Some more info would be good. 1. How many miles? 2. How are you reading code? 3. How did the Coil look when you changed plugs( very common problem) From what you said i can assume the next place I would go is the coil.
Sounds like a Cyl 8, misfire.
I found the easiest way to do this is read the codes, if it is reading a misfire on one cylinder, then swap that coil pack with one of the other cylinders coil packs, then you will have to clear the codes and drive it, then see if it throws a new code on a different cylinder.
Probably the number two ignition coil. Also check the spark plug and the wiring to the coil.
It may be your spark plug in that cylinder. It could also be the spark plug wire to that cylinder or the coil pack. Those are the first places to look.
That was a good test if you had a Model T Ford. Using kerosene washes all the oil away from the piston, piston rings and cylinder walls. Not a good idea during start up. These days we use a compression gauge. Take a compression reading of all cylinders with spark plugs out, coil(s) and fuel injectors disconnected. If the first compression reading on a cylinder comes up low, squirt some motor oil into the cylinder and take a second reading. If the reading doesn't change much you have bad valves. If the reading goes up substantially you have worn/cracked rings. What you want to see is all the cylinders having a reading within 15% of the highest and lowest readings.
Probably not check coolant sensor and injectors how is EGR working The computer and wiring are both possible causes.
Water in a glass graduated cylinder adheres to the sides of the cylinder, forming a meniscus which is an upward curve. When reading volume in a cylinder, look at the meniscus at eye level. Read the volume at the bottom of the curve.
Now reading is a conversation of give and take.
It is your fuel injectors. My car had a lot if miles. About120.567 miles this man at auto zone told me to use that. But never asked how many miles I had in my car. Needless to say. My mechanic had to change my fuel tank dropped my gas tank which was shooting rust into my fuel injectors. They had to be changed. Good. Do your reading and DO NOT put it if your car has a lot if miles cause then next fuel injectors will be in danger. Hope this helps
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The reading on the graduated scale is taken before and after the metal is lowered into the cylinder . The second reading is subtracted from the first. This gives the volume of the metal in cubic centimetres.