I have a 2001 civic ex w/ a 1.7 SOHC vtech it started about 2 months ago and keeps misfiring only on cylinder 4.
did a full tune up and coils, replaced all fuel injectors(refurbished), timing belt component was replaced 1 year ago. Checked for oil in radiator and oil for coolant.(None). Little hesitation and stumble when idle, run and drive fine when car running on the road. Its always the #4 cyl. That I have a problem.
when engine running, ill pull out coil on cyl#4 engine runs same but on others coils it stumble.
notice the #4 plug is full of carbon maybe will help on your advice. Car was always maitained and all records are kept. Should I consider a pro mechanic or its time to replace?