Replacing the spark plugs used to be a chore that occurred every few oil changes at best. It used to be one of the easiest repairs for the do-it-yourself handyman. Spark plugs are, by nature, on the outside of the engine. In a standard rear-wheel drive car or truck, they face sideways and up and are easily identified by the wires leading from their top back to the distributor cap. All you needed was a spark plug wrench, some new spark plugs and some quality time to spend with your car.
Many modern cars break all of these assumptions. It has become much harder to repair most spark plugs; especially in front wheel drive cars but in return spark plugs have been made to last much longer — longer in many cases than people will own their cars. Front wheel drive cars turn their engines sideways (which points some of the spark plugs to the rear). Newer cars have far less space available under the hood (which means everything harder to get at).
Today’s discussion is about the Ford Taurus. Our particular sample is my 2002 SEL, but I’m led to believe that this engine is packed in similar ways into a number of front wheel drive Ford and Mercury cars including the Sable. My partner has a 2001 SE that has coil-on-plug. In his case, there is a procedure using universal joints and extensions that will allow you to remove the spark plugs without going though this rather lengthy procedure. You have coil-on-plugs if your spark plugs are topped by a round cylinder that is screwed to the top of the engine. My engine has the screw holes for COP, but it definitely has a coil-pack and that coil-pack is in the way of the universal joints and extensions plans (which my partner and I executed successfully on his car, BTW). The picture here shows the front three sparkplugs at the bottom — with no coil-on-plug.
Assuming you have the same Taurus or Sable, here’s how I got it done…
The first three plugs (numbers 4, 5 and 6) are easy. They’re right in front of you. If you can’t find them in your engine, it’s a foregone conclusion that the rest of this is too complicated. Change them. I was cautioned that the engine should be cool or cold (to prevent stripping of the threads (really bad)) and that I should replace with OEM parts. The OEM spark plugs were only $8 at the dealer, so it’s not too painful.
Now the back three will take us the rest of the time — a few hours for the first try. We need to remove the plenum or upper intake manifold to get at them. There’s a few tricks to this. One trick that I didn’t learn until the second or third time that I removed this plenum was to remove the EGR (Exhaust Gas Recirculation) valve before doing anything else. The exhaust gas is hot which requires that the hose is rigid. This rigid hose and valve makes it extremely hard to remove and replace the plenum. You’ll note in the picture here that it has two nuts and two bolts. It also has two gaskets and they were badly worn in my case. You should make sure you have new gaskets on hand for this part at the very least. If you’re having trouble locating this picture in your engine, the EGR is situated between the throttle body (the thing that moves when you press the accelerator) and the plenum.
Now, before removing the plenum bolts, there are two connectors on the passenger side (one wire and a double pipe hose) that you should remove. On the driver’s side, I remove the air filter housing because it’s easy and I disconnect the forward facing PCV hose (a rigid hose that connects to the forward valve cover). There is also a large and a small hose that comes straight down from the throttle body. The small hose is easy to remove (pull down, but you’ll be doing this by feel). The large hose does a 90 degree turn and immediately plugs into a rigid section that, in turn, plugs into another hose that sits in the valley of the engine. It is massively easier to disconnect the small rigid hose (as either end) than the large end that connects to the throttle body. Disconnect this.
One of the videos I found on the web went as far as disconnecting the throttle cable and removing the throttle body from the plenum (he removed the plenum to the bench). This seemed like a lot of work to me. I just removed the 8 bolts holding the plenum down and raised it up — supported by a handy bit of 2‑by‑4. Note in this image the 4 (out of 6) orange gaskets. This is a bitch of a design. They fall out easily. Keep careful track of them. Do not let one fall in the engine. I had also bought new gaskets for this, but the first new set I got didn’t fit well at all (which made them fall out more). A second set fit better, but it may have been better to leave the originals in there. In my case, I was also facing a vacuum leak, so they needed to be changed.
Once the plenum is up, you’ll be able to access the three rear spark plugs. That part is fairly easy. Remember to be careful threading your sparkplugs in (by hand at first) because a cross threaded spark plug means an expensive repair. Again, my source material said that a cool engine is less likely to cross thread.
Putting things back together is largely the reverse of what you just did. I applied some light grease to the gaskets to keep them in the upper plenum as I replaced it. If you didn’t remove the EGR, you’ll need to bring down the plenum forward of where it goes, get the EGR inserted and then shift it back. This is when the gaskets break loose and go down the lower intake tubes. Not fun. If you did remove the EGR, it is easier, but not foolproof. I found this easiest with a helper using a shop light to watch the gaskets when I lowered the plenum and then inserted the first few bolts while I held down the plenum. Note that these bolts are spec’d to 10 ft-lbs — quite light. I managed to break one at one point in my odyssey. You might want to avoid that.
Put all the hoses back on where you found them. Remember the two on the passenger side. Replace the EGR and be careful with its gaskets. If you start the car and everything runs horribly rough, chances are you forgot a hose or misplaced a gasket.