[UncleBob]

never rely on a misfire code to be stored when there really is a misfire.

Some computers are very sensitive to misfires. Some computers are completely blind to them. This has to do with the parameters the factory programs into them. There are many OBD2 cars that you can literally disconnect 2 spark plugs and drive it and it will not set a misfire code.

You are discribing a misfire, regardless to what the computer says. The old-fashion way to narrow down the cylinder the problem is, is to use a pair of insolated pliers and pull wires one at a time while its running, and find the cylinder that doesn't change the idle quality when you pull it.

The much more accurate way is to find a shop that has an ignition scope. This will at the very least tell you which cylinders(s) are the problem. Depending on how educated the tech is, a lot of times the patern of the ignition will give you a strong hint to what the misfire is caused by also.

It very well could be a simple fix. It might be internal engine problems. I wouldn't recommend blindly replacing coils and other components, since as you have already discovered, that gets rather expensive. Spending $400 on parts to fix a problem that doesn't improve anything, makes the diagnostic fees from a good shop not look so bad