How do you change spark plugs on a 2005 Mazda 3?
June, 2009 - I just changed the plugs on my daughter's 2005 Mazda 3, so I will give my experience. The engine should not be hot - may be warm or cold. Start by disconnecting the negative terminal from the battery. Now remove the black plastic cover from the top of the engine. It snaps into place, so just pull straight up. The four cylindrical gizmos are the coils which mount directly above the four spark plugs. There are no ordinary plug wires per se. Remove the four bolts (studs) that are securing the coils, and pull the connections straight up off the sparkplugs. Remove the plugs with a deep socket, or sparkplug socket. You may have to grasp the plugs with a needle nose pliers to get them out after loosening them. Replace with NGK ITR5F13 sparkplugs. (I would have the auto parts store verify the plugs you need for your particular vehicle.) My experience was as follows: Advance Auto Parts sold my daughter some Bosch Platinum four-prong plugs #4459. I installed these in the car. Two days later the check engine light came on. Advance Auto Parts then sold her some Bosch Iridium plugs. Given my previous experience, I tried to find NGK plugs. Neither Advance Auto Parts, nor Autozone had them, so I bought and installed Autolite XP-104 Iridium single-prong plugs. They seem to be working just fine, although the service manager at Mazda told my daughter that they will "burn out pre-maturely" and to use NGK instead. When installing the new plugs be sure to put some anti-seize grease on the threads. I read that this is an aluminum head on this engine, so you had better be careful. You DO NOT want to strip the threads. Tighten the plugs to the specified torque (I do not know that figure). The Autolite plugs said to hand tighten and then go 1/16 turn beyond that. Err on the side of too loose.