My car trembles only while idle and check engine light is on with code P0303 cylinder 3 misfired. When RPM is 1500 or more it runs fine.
Here is what I have done:
1. Changed all 6 spark plugs.
2. Checked all wires going to ignition coils.
3. Changed ignition coil on cylinder 3.
4. Checked for sparks on all 6 cylinders when engine is idle. They all look the same.
5. Checked for vacuum leak.
6. Visually inspected intake manifold gasket. It looks ok.
Then I started to disconnect fuel injectors one by one. Disconnecting 1,2,4,5,6 give a much bigger shake. When injector # 3 was disconnected I didn't see much of a difference.
Today I added Dura Lube injector cleaner. It's gonna take me at least a week to use a full tank. If a week later my car still shakes, what can I possible do? How likely it is to have a bad injector at 122k miles. Is it a big job to replace it? Any other suggestions are greatly appreciated.