This is the third, but possibly not final installment of our 2002 Taurus repair adventure. Here our goal is to get at the gaskets between the lower intake manifold and the cylinder heads. Poor running at idle often indicates vacuum leaks and these gaskets are the last culprits we can point to. They’re also the most difficult of the intake gaskets to reach. Our internet research tells us that the lower intake manifold gaskets are a common problem on the Duratech engine made by Ford.
One note: if you’re going to remove the injectors, it’s best to shut off the gas supply and the easiest way to do that is to unplug the rollover switch which is near the trunk light on the passenger side wall of the trunk. It’s also worth noting that releaving the pressure of the fuel system is easiest done by running the engine — so you’ll want to have done this before completing even the first step. However, if your fuel rail or injectors are already leaking, shutting off the fuel supply is sufficient as the pressure will run out. The fuel system is under about 40 PSI pressure and gasoline is nasty stuff. Nota Bene!
Air for the engine comes in through the filter (a square box right of the engine … just outside of this picture). The MAF sensor is in the round tube leading to the throttle body (where the light is pointed, roughly, in the picture). Then the air is distributed forward by the six ducts that are roughly in the middle of the picture. We took this whole assembly off in the upper intake plenum and spark plug post. This post assumes you’ve removed the upper intake plenum as described in that post.
For some reason, Ford decided to split the upper and lower intake. It may be a nod to the difficulty of placing the intake back on the engine or it may be simply required by the manner in which the injectors and fuel rail are fastened to the lower intake. In the picture you can see the two halves of the lower intake in place. The injectors and the fuel rail have been removed from this picture. The gaskets we’re after are on the bottom of these two plastic bits.
Removing the fuel rail is 8 bolts — 4 short and 4 long. The long bolts go through the lower intake into the cylinder head and the short bolts go into a captured nut on the inner side of the lower intake. The next step is a little scary the first time: you pull up on the right end (the left end of the fuel rail attaches to the gas supply) of the fuel rail hard enough to either pull it from the injectors or pull the injectors out with it, or a little bit of both. In the picture, we’ve covered the lower intake manifold with two rags to prevent little pieces from falling into the engine. This is particularly important for parts like the O‑rings on both ends of the injectors. The amount of force required to remove the fuel rail is surprisingly large until you struggle to put it back in — it’s one of those design choices that make you want to force car design engineers to work on their own products. Once you have removed the 8 bolts, there is nothing else holding that rail but friction.
At this point, only two bolts (each) are holding the lower intake in place. Removal and replacement is easy. As before, we used a little grease to stick the gaskets into their channel as the gaskets have a propensity to fall out when we’re trying to put the intake back in place. It is always very important to make sure you don’t drop anything (like the gaskets) down the intake.
It’s worth spending a little time talking about the fuel rail. I had replaced it 3 times before we stumbled upon the method we’ll talk about to replace the fuel rail and each time the rail leaked around the injectors. At one point, I thought that we had damaged the fuel rail and called around to find the cost of a new one. Truth was, nobody stocked or could even order it. The Ford dealer said it was considered a “vintage” part and would need to be ordered from that division. Since nobody in the aftermarket makes the part, I have to assume that failure is very uncommon. If you encounter a leak, pull it off and try again — it’s not the fuel rail. It may, however, be a bad injector — but there’s only a few places they can leak from. In one installation, we did destroy some O‑rings. It’s a good idea to have a new set of O‑rings ready for this job.
Obviously, if you have a bad injector (you’re doing this repair due to a code that indicates a bad injector in a certain cylinder), you would replace it now. If you suspect a bad injector, rotating them to different positions it possible. Our set of injectors do have different codes on them, but since we have 3 of one code, 2 of another and one of a third code, I doubt there is any specific placement for them.
The problem we’re going to have replacing the fuel rail is that half the injectors slope forward and half of them slope aft. They cross each other before reaching the “hats” that they seat into on the fuel rail. From some research and a video online, I had been prepare to “work” the rail on from the fuel line end (left) to the right end. I never actually got this technically to work. The procedure is to install the injectors (note that they’re keyed to ensure proper orientation) and then work on the rail one injector at a time.
After three failures of this method, we talked about inserting the injectors into the rail and then pushing them into the intake. On engines with 4 cylinders, several sites and videos advised this was easier. It’s not possible with this engine as the injectors cross. In the end, we settled on a compromise that worked well. We inserted the injectors into the intake only partially — such that the key was level with the top of the intake socket. We then were able to use the increased play in the loose injectors to work the rail onto them. With all injectors inserted into the rail, we then pushed, wiggled and worked the whole result until the injectors were properly seated into the intake holes. Again here, watch the injector key tabs — they need to line up with the lower intake holes properly.
Another thing to watch for is the O‑rings. We found they would sometimes bulge below the “hats” of the fuel rail. We used a slot screwdriver to coax the O‑rings up under the “hats” as we were working the whole thing down. On one failed installation, not doing this resulted in some of the O‑rings being cut down on one side by the metail of the “hat.”
Since we had several failed attempts we identified an earlier way to know if we had done things right by the injectors. Rather than finding a leak after everything was reinstalled on the engine, we again deployed the rags (to catch leaking gasoline) and reconnected the rollover switch in the trunk. Then we switched the ignition to on (do not try to start the engine here). This will pressurize the fuel rail and show any major leaks immediately. If you discover a leak, disconnect the rollover switch again, wait for the pressure to dissipate out your leak, remove the fuel rail and start again.
Lastly, you’re going to replace all the parts of the upper intake plenum in the manner described in the other article. If the engine runs rough at idle, you still have a leak somewhere — a hose you forgot or a gasket that fell out. I’m pretty sure I could do this repair easily the next time, but I had to take several runs at each of these problems before I got it completely correct.