The symptoms of defective coils depends on the car in question. It could be a misfire, backfiring, burnt gasoline smell, or starting issues when your "Check Engine Light" turns on. This appear on the dashboard as a CEL. Prolonged engine misfire the catalytic converter and can lead to engine detonation. When replacing ignition coils it is best to have them replaced all at once. Keep in mind that if one of the coils goes defective, then the others are probably going to be defective in the near .The number of ignition coils in the car depends on the car engine, model and year. Do not assume all vehicles are the same.fit and work like the factory part. DIRECT REPLACEMENT/ UPGRADE over your stock coils.This makes our product and reliable under extreme conditions while providing High Electrical Resistance, strong Spark from plugs, and being to and Abrasion.Our replacement ignition coils are easy to install with the highest quality copper. Item Type:Ignition Coil Replaces The Following Part Numbers: UF401 IGC0007 610-58649 22448AL61C 22448-AL61C C1439 5C1430 178-8317 6734025 GN10246 Vehicle Compatibility. Fits The Following Vehicles With 3.5L V6 Engine 2003-2008 for FX35 2003-2007 for G35 2006-2008 for M35 2003-2006 for 350Z Colour:Black Material:plastic Package Contents: 1 * Ignition Coil Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.