Ford Repair: 2000 Crown Vic P.I. 4.6 liter engine miss fire, bosch platinum, brake torquing

Question
Hey Shaun, I would hate to have to take this vehicle in to get a diagnostic from the FORD garage. $60 !! I switched the coil packs around. When I did ... one of the ones I am assuming is bad, fired only a little bit. In the position it WAS in ... it wouldn't fire at all ?  Is it possible it was getting a bit of connection in the cylinder I switched it with ? The service manager at the FORD garage was a bit tight lipped. I understand they are there to make money. But geez, I am trying to help out a friend who don't have alot of money. I want to think it is the coil packs ... BUT, I did NOT replace with MOTOCRAFT ... I used BOSCH PLATINUMS. Tomorrow I plan to take out the plugs and look at them ... not real expensive to replace them with MOTOCRAFT ... so I will do that too. Is there any other advice you can give me ? The service guy also told me that from what I told him and have described to you that it didn't necessarily mean it was bad coil packs. I thank you so very much ... my friend does too ... she don't have alot of money ... we are trying to get out of this as cheap as possible !  KUDOS DUDE ! This site ROCKS !

Answer
Hey Tim,
     I'm glad you were able to use some of that info. Now let me get this straight, you switched a known good coil from a cyl. that is firing all the time and the cyl. you put it on misfired? If that is the case, look at the connection for the coil primary, especially if it is on cyl. 4 (pass. rear). The cylinders that are misfiring under load (driving and brake-torquing) are the ones that you attack first by singling out bad parts one at a time. If the compression is good on that cylinder, then it is most likely a cracked plug  or a closed plug gap, with a bad injector or the control circuits for the coil or injector being the least likely. The Motorcraft #SP-432 is the ONLY plug I have had any luck using in that engine. Bosch platinum doesn't promote good idle quality because of the insulator design(good for Benz vehicles though), which is part of what it sounds like what you are fighting in part. Repair the "dead" one(cyl. which never fires AT ALL) first and then install those B.P.'s in the garbage can and the idle should get better. Also check for vacuum leaks, clean the throttle body bore out, and replace the PCV valve for idle quality. The boots that connect the coil to the plug can deteriorate and allow the spark energy to travel down the plug to the shell of the plug, so check for carbon tracking down the side of the old plugs and the new ones you put in. Those boots come with a new coil and can be replaced separately which I always do when replacing plugs on a Vic/Marquis/T.C. with more than 60k miles no matter what. If that boot fails, it ruins that coil immediately, which could have been the start of your problems to begin with. I really hope you guys can get this thing running better!