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.

Credit Where Credit is Due

2010 Acura MDX

It might seem at times as if I'm unduly harsh on the automakers, constantly pointing out their shortcomings, oversights, and failures. Perhaps, though I'm equally happy to call attention to positive attributes when they present themselves.

To that end, allow me to introduce the 2010 Acura MDX seen above. Built on Honda's large utility platform (shared by the Acura ZDX, Honda Pilot, Honda Ridgeline, and Honda Odyssey minivan), this particular "YD2" version was produced for the 2007 to 2013 model years, and I'd expect the earlier and current versions to be similar.

It's not that these are perfect - another customer of mine had a 2008 model that needed all 4 of its fancy magneto-rheological shocks/struts replaced (leaking/failed) - a costly enough proposition on its own that it got traded in, rather than tackle that and some other upcoming maintenance/repairs.

What deserves mention in the MDX is ease of service of the driveline's fluids.

Fluid changes are a regular maintenance item, regardless of whether your vehicle's literature suggests that the transmission is "sealed for life" and the intervals for the differential and transfer case are either not provided at all or in the 100,000+ km range. Look closer at the severe service schedule for a more realistic view.

In some vehicles, fluid changes are a major pain. Yes, domestic automakers, I'm looking at you. Dropping a fluid-filled pan counts as a major pain - it's extremely rare for there to be a drain bolt, let alone one that's not completely seized in place and/or equipped with a fastener whose head is made of a material only marginally more robust than sun-softened butter. It's a fantastic opportunity to bask in the joy of spreading used transmission fluid all over the floor and - often as not - yourself while trying to balance a shallow, fluid-filled pan as you undo the last one or two fasteners and lower it into the drain bucket.

2001 Chevrolet Impala (3.8) engine bay from below - a typical domestic setup. That silver pan holds about 4 litres of fluid - think you can undo and lower that without spilling it?

In every Honda product I've ever seen (not counting the US-only Passport, which was a rebadged Isuzu Rodeo; I worked on one once), automatic transmission fluid is drained by undoing a single drain bolt.

The MDX's automatic transmission fluid drain bolt...
In most recent Hondas, the head of this bolt even incorporates a 3/8" square drive that any standard ratchet or extension fits into. Visually different from the other fasteners, there's no mistaking its purpose. action.

If there's criticism to be leveled here, it's that some fluid ends up on the crossmember that runs below the transmission. I can live with that. However there's no way to change the filter (an internal screen), which isn't ideal, nor is the fact that only about 3-3.5 litres of the approximately 10 litres of fluid this thing holds get changed this way. Short of disconnecting a cooler line and using a fluid exchange machine, you won't get all of the fluid out of any conventional automatic during a service, so it will have to suffice.

Where Honda cements its victory here is in how the fluid gets replenished. Others require you to refill through the dipstick - a sometimes tedious process that's only better than the alternative of no dipstick. In older Hyundai/Kia automatics, you've got to add the fluid s-l-o-w-l-y or it burps back out the dipstick. Honda's solution in this application?

Acura MDX automatic transmission fill bolt.

How about a nice big top-mounted bolt marked "ATF"? A long funnel fits in beautifully, and with a large hole, it'll take fluid as fast as you can pour it in. Access could be slightly easier, but in the grand scheme of things, this is heaven. I will concede that the actual dipstick, which is mounted low down on the front, could be a bit easier to reach.

That's not where the thoughtfulness ends, though. There's still a transfer unit (splits power from the transmission and sends it rearward) and a rear differential, which on the MDX, also contains the clutches that control rear torque bias and SH-AWD power application.

Acura MDX Power Transfer Unit - see the drain and fill plugs?

These power take-off units normally don't contain very much fluid, so what fluid is there leads a harsh life. In the 1st-generation Nissan Murano, they're also known to leak, followed shortly by failure. Unfortunately, Nissan has chosen to make it terribly awkward to check, let alone fill, the transfer unit. They could stand to learn from Honda in this instance. Honda's drain and fill are both nice and obvious and accessible. The required fluid type (hypoid gear oil) is even cast into the housing next to the fill bolt. Nice!

How about the rear differential?

Acura MDX rear differential. More of the same. See the wiring for the clutch pack actuators?

Just what you'd expect, if you were working your way back from doing the other two services. A clearly marked fill bolt ("ATF"), and an obvious drain bolt. Access is trickier here because the rear crossmember and spare tire are right behind the diff, and the floor above makes the use of a funnel impossible, but there is a nice window cut into the crossmember immediately behind the fill plug, so a suction gun or the pressurized fill device of your choosing can get a clean, straight shot into the hole to refill it.

I have to ask myself, how much does it add in cost to cast lettering into the housings, or punch an extra opening into the rear crossmember to facilitate servicing? Probably nothing, or close to nothing. As for designing these components and those around them to make them accessible, how much extra would that cost? As a consumer, the time it takes to do these maintenance procedures does cost you. Would you pay an extra $100 or even an extra $500 up front if you knew that down the road you'd get that and more back in reduced labour? At least when it comes to these items, Honda apparently thinks you would. Good on 'em. Credit where credit is due.