Engine Performance problem
2005 Other Honda Models 4 cyl Front Wheel Drive Automatic 142000 miles
The fuel economy deteriorated on my honda jazz. Spark plugs were overdue for service 20,000 km ago. When changing plugs I noticed some of them have rusty discoloation and rubber cap on the coils seem overheated (2 of the 8 plugs). Honda jazz uses 2 plugs per cylinder. It was suprising that the other plug in the same cylinder did not have marks/did not show symptoms of overheating.
Do you think it is defective coil that caused spark plug to deteriorate, or it was defective plug that caused the coild to deteriorate? Are the colis with signs of overheating are likely to be defective / have to be replaced?