Re: 1998 ford crown vic tune up
There are tune ups and there are TUNE UPS. You should not have to replace any coils for a good tune up, unless of course, one of them is faulty and causing a miss or check eng code.
A fresh set of plugs (use anti-seize and a torque wrench!) and a coil kit (new boots, springs and resistors, use dielectric grease) and a fresh air cleaner are about all that's required. It's also a good time to remove the throttle body and carefully clean the crud that tends to build up inside, but do so carefully. I use a soft shop towel and WD40, nothing abrasive. It's also a good time, since you're under the hood and greasy anyway, to check the PVC and EGR and cooling systems.
I replace all belts, hoses and coolant every four-five years. Don't forget the heater hoses. I have four Panthers, my '92 has over 400,000 miles of reliable service with just routine maintenance, a few small parts and a trans rebuild, and that's with my kids driving the car!
I usually see at least a 1 MPG increase with fresh plugs.