Thursday, May 1, 2014

Learning Something New

2006 Ford Escape 3.0L

This was something I'd never seen before. The 2006 Ford Escape V6 seen above belonged to a new customer, and it had made it to our shop under its own power, but just barely, running on at most 4 of its 6 cylinders. Truthfully, I'm amazed it did make it, because it took several attempts to reverse it up a slight incline to get it out of its parking spot and bring it in.

Like virtually all modern gasoline powered vehicles, this particular model uses individual coils for each cylinder, located immediately above the spark plugs, a design known as "coil on plug" (COP). Ford's COP systems seem to be more failure prone than most, though everyone has these things fail from time to time.

So the coil failures were nothing new. This truck had codes for the control circuits on two of the affected coils, which of course would be on the rear bank of cylinders, necessitating removal of the upper intake manifold or plenum.

Upper intake manifold removal is necessary to access the rear 3 coils and plugs.

The process is actually not as bad as it looks. I'd be happy if they were all this easy. Of course, I'd be happier if I didn't have to remove it at all, but hey, I'll take what I can get; Ford making something easy is a rarity.

That can't be good!

As you can see from the heavily-fouled condition of the spark plugs (above), this had been going on for quite a while. Seeing this, we readied the customer for the possibility that he had actually injured the motor, or at the very least, the rear catalytic converter, by continuing to drive it with the dead coils.

Here's where it gets interesting: as part of the diagnostics, prior to removing the upper intake, I'd already checked to see if our two dead coils were being triggered by the PCM (powertrain control module) - you can see it in the second picture; it's the box in the firewall with the three square plastic connectors on it. It wasn't firing them, though that could have been because the circuits or coils themselves were bad, so the PCM was protecting itself. Substituting a noid light (a circuit tester) eliminates that, and it revealed that the PCM simply wasn't triggering them, so the computer itself was bad.

While it's easy to replace - two bolts, three plugs! - a PCM for this vehicle is around $1000, and it then has to be programmed, which is another roughly $150. Ford has a bulletin that states that it will not warranty the new PCM unless all six coils are replaced. Apparently the coils kill the PCM - I've never heard of that happening before. Normally the internal circuitry in a PCM is robust enough that it will tolerate all kinds of punishment. A quick Google search suggested that this is not all that unusual in these vehicles. Who knew?

As it turns out, there's a firm in Toronto that will repair the PCM for a few hundred dollars, replacing the burnt-out coil drivers on the circuit board. This also negates the need for programming, since the computer is already programmed, and that part of it is OK. You just have to ship it out and wait a week or so for it to come back. In this case, time saves money.


Six new plugs and six new coils, ready to go... (Note Ford's unusual cylinder numbering system)

This repair worked out. Six plugs, six coils, and a repaired PCM later, this Escape ran fine, and it appears - in the sort term at least - that both the engine and the catalytic survived their ordeal.

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