How To: Ford Crown Victoria Tune Up / Check Engine Light (Coil Boots and Spark Plugs)
My first experience with buying a Police Interceptor. In that post, I mentioned a Check Engine light and a nasty misfire, but I glossed over the actual repair procedure. Well, I recently got another P71, and it too had its Check Engine light (also referred to as a CEL or MIL) illuminated. Due to popular demand, I’m going to explain how I fixed it- and how you can fix yours, too.
This procedure applies to the most common cause of rough running / check engine light on Crown Vics: misfires caused by bad coil boots. In extreme cases, the light will actually flash, meaning that you will damage your catalytic converters if you continue to drive. Another symptom includes P0300 codes (misfires) like P0301, P0302, P0303, and so on.*Even if your check engine light isn’t on, this is the procedure to follow when your Crown Vic needs a “tune up,” something that should be done when your car runs rough, or every 70,000 – 100,000 miles.*
Newer Ford vehicles (all Crown Vics from 1998-on, F-150 trucks, Explorers, etc) don’t have spark plug wires. This can throw some people for a loop when they go into the auto parts store and ask for wires, only to find out there aren’t any!Instead of using a single coil with a distributor and wires, each cylinder has its own coil. There’s no distributor, either. It’s called Coil on Plug, or COP. The system can seem challenging at first because it’s not what most people are used to. But in reality, it’s actually easier to repair- once you learn how it works.If you have a check engine light on, start by retrieving the codes so that you know what the computer is telling you needs work. If your light isn’t on (i.e. you’re just ready for a tune-up), you can skip this section.
You’ll need a code reader for this. Code readers are increasingly affordable- or you can borrow one from a gearhead friend. I prefer Innova code readers, but any brand will do the job. Amazon.com has great prices on readers. You can check out mine here. For the price, I like it. It gives freeze frame data like speed, temperature, and RPMs when the code was thrown, and it explains the code on-screen so you don’t have to Google each code that pops up. It also has the capability to run Ford KOEO and KOER tests, which I’ll touch on in another post.
The connector should be located right here- to the right of the steering wheel, very close to where your knee would be when driving. Some police departments move this when they install all their electronic gizmos, but it won’t be far from this location. I believe civilian Vics have their port here, too.Plug your code reader in, following the directions that came with it.Waiting for the code(s) to appear…. Mine didn’t have any codes because I had already cleared them. Any P030X code is commonly caused by bad coils and/or coil boots. The last number (which I signified with X) in the code is the cylinder number that is misfiring- for example, a misfire on cylinder number 8 would be P0308, cylinder number 7 would be P0307, etc.
Ford V8 cylinder numbering chart (obviously made by a professional graphic designer, right?)
Example: P0306 would be a misfire on cylinder six, which is the second from the front on the driver’s side.
Now that we’ve figured out where the problem is, let’s figure out what’s causing the problem- and fix it, of course!
There are basically three things that can cause a misfire code on a COP system.
A bad coil boot (pictured above), allowing the spark to arc out, resulting in a misfire.
A bad coil pack that delivers weak or no spark, resulting in a misfire.
Extremely worn plugs.
An issue with the cylinder itself- low compression from a burnt valve, worn ring, etc. This is the worst case scenario and it’s also the least likely- but it does happen.
To determine which one of the three problems you’re having, you’ll need to take some stuff apart. Don’t worry, it’s not that hard. If you’re mentally disturbed like me, you think it’s fun.
Step One. Remove the air intake tube.
Simply unplug the two hoses on the back and unscrew the two clamps, then set the tube aside.
Step Two. Unplug all of the coil packs from their wiring harnesses.
If you’re in a big hurry (a.k.a. stranded by the side of the freeway), you can just check the one coil pack that is misfiring. But to do this job right, you should check the entire system. Be gentle with the connectors; they can get brittle over time. Just squeeze and pull to disconnect.
While doing this, take a look at the top of the head in between the valve covers and the intake manifold. Do you see antifreeze? Intake manifold failure is quite common on Crown Vics, and it will cause a misfire on multiple cylinders. To correct this, you’ll need to replace the intake manifold. It’s not impossible, but it is a full day’s work— not something I’ll cover here.
Step Three: Unbolt and remove all of the coils.
Most Crown Vics will use 8mm bolts here, but many that have replacement intake manifolds will use Phillips screws or a different size bolt. Note: Coils aren’t cylinder specific, so there’s no need to mark them or put them back where they came from. They are all identical.
Most of the coils will come out with the boot and spring attached. Sometimes, the boots remain stuck in the plug well. No big deal, just pull them out with pliers.Don’t even think about loosening those spark plugs before you clean the wells! If you don’t do this, all the dirt and crap inside the plug wells will go right into your cylinders- not a good idea. An air compressor makes this easy, but your wife/mom/aunt/grandma’s vacuum will work, too.
Step Four. Remove the spark plugs.
Again, if you see coolant down in there, you probably need an intake manifold. It’s not the end of the world, I promise. If there isn’t coolant, continue on. To remove the plugs, use a 5/8″ deep socket and an extension on your ratchet. As you remove the plugs, watch for oddities like plugs that are blacker than the rest, or whiter/cleaner than the rest. This can be indicative of a problem with the cylinder. Otherwise, just toss them.
Step Five. Gap the new spark plugs with a gap tool.
Improperly gapped spark plugs won’t work well. Ford spec is .052-.056. This will be on the emissions sticker near your radiator, too.
Step Six. Hand tighten – yes, hand tighten – the spark plugs.
Once they’re hand tightened, tighten them to 14 lb/ft of torque. Don’t overtighten or undertighten spark plugs, especially on a Ford 4.6- they are well-known for throwing spark plugs out of the head, causing a very expensive problem. There’s no excuse not to have a basic click torque wrench with today’s modern cars.
Step Seven. Pull the old boots and springs off the coils.
If desired, spray some electrical cleaner on the coil contact (shown above). Firmly seat the new springs in the coils and put some dielectric grease on them to prevent corrosion. Slide the rubber boots over the springs.Reassemble it all. Reverse of removal, of course. Do not overtighten the bolts on the coils- it is easy to strip the threads in the intake manifold. Reinstall the intake tube, and start up the car!
Drive around and see how it runs! If you get another check engine code, you probably have at least one bad coil. Here’s an easy way to determine which coil(s) are bad.Let’s say you have code P0305 (misfire on cylinder 5). After checking the connections on cylinder 5’s COP, just swap #5 with #3, or #2… or any other cylinder that’s not throwing a code. Erase your misfire code, then restart the car. If the misfire code moves to the cylinder that you moved the COP to, you have a bad coil. If not, you have an issue with the engine itself. Quick note regarding coil packs: Surprisingly, Amazon.com is one of the cheapest sources for replacement ignition coils, provided you can wait for shipping (3-4 days) you can get a whole set of 8 for under $90, which is just ridiculous. If you’re in a bind and can’t wait, you can still save some money by using the Advance Auto Parts links at the top of this article.
If the light stays off, congratulations! Your car probably runs a million times better. You’ll get better gas mileage and loads more power, and you saved a ton of money in the process. Assuming that you used Platinum spark plugs (Ford recommends them), you should be good to go for the next 100,000 miles! Did you find this guide useful? Comment here!