Would Check Engine light be flashing or solid if the ignition coil was the cause

Hello, the problem here is that if you can't confirm it's the cylinder 1 coil that is at fault, then why replace it? I'd want more information as to what diagnostic process was followed. If it's a "guess" based off of a trouble code, then I'd prefer more diagnostic information before replacing the coil. Sure, you could have cylinder 1 coil causing a misfire -- which indeed would cause your check engine light to flash -- but you could also have a faulty spark plug. You could have a fuel injector issue. You could have a valve train issue. You could have a base engine issue on cylinder 1. It's all a "best guesstimate" until you have actual data proving the coil is bad. For example, they could swap coil #1 with coil #4 and see if the next time it malfunctions, a code for cylinder 4 sets instead this time. In any case, -- to answer your questions: 1) Check engine light could very well be flashing with a misfire, but in some cases could be solid -- regardless of it being a coil or not. 2) Replacing all 4 spark plugs is a good practice when replacing any coils. Plugs should be replaced uniformly at the same time. Agreed with driving the vehicle until a failure again occurs; what if the light doesn't come on again for another 5,000 miles? I'd wait, it won't hurt in the short term. But do not continue to drive a vehicle that has an active misfire. That will cause further issues. Hope this helps. Good luck. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops