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Ford Windstar Breaking Spark Plugs

Q. Hello Vince, This one has the local Ford dealer stumped. We have a 2000 Ford Windstar with about 40,000 miles on a new engine (replaced under warranty due to rod bearing problems) and 104,000 total miles. A few months ago, it started jerking occasionally while going uphill at a steady speed.

Ford Windstar Breaking Spark Plugs

Their first "fix" was new plugs and wires, and a reprogram of the computer. A couple of weeks later, the same thing happened. They discovered, after a road test and hooking up a monitor of some sort, that cylinder 3 was misfiring. The cause was plug number 3 was broken, the porcelain cracked I believe, and so they replaced the plug.

A week later it happened again, and we took it in again, and got a new plug. This cycle repeated about half a dozen times, until the last time it went in a month or so ago. They took the head off, inspected the pistons, cylinders, head, etc., but could find nothing wrong. They resurfaced the head and did some valve work, and re-assembled the whole thing. This lasted until about two weeks ago when the problem returned.

As an aside, this engine knocks severely when using anything but premium gas--we use that exclusively now, and we notice no knocking. I did some research on that and found out that knocking (actually "detonation") can cause broken plugs due to the force of the pressure wave from the secondary explosion.

Can the computer be programmed so that the engine is less sensitive to octane rating and thus less likely to detonate? Could their "reprogramming" be responsible, even in part, for this?

Anyway, we are sick of return visits to the dealer who apparently is grasping at straws--they have no idea what to do. Fortunately we took the car in the first time before the 100k warranty expired, so these repairs are all covered, but I just know they are about to tell us to get lost.

To beat all, after the last "repair," the A/C switches from vent, where the knob is set, to floor, then to defrost, all on its own, whenever we go uphill. Yesterday, the interior lights started flashing all by themselves too.

Are these problems related? Is the van possessed? If we weren't upside-down on the thing, we'd trade it today. Any help would be greatly appreciated!!

Thanks in advance,
Knoxville, TN

A. There were some TSBs issued to address this problem, but since you did not tell me what engine you have, I don't know which, if any, would apply to your vehicle. Have your Ford Dealer look them up and see which apply.

Number: Date: Title:
02-24-3 12/09/2002 Engine Controls - Spark Knock on Acceleration
01-9-7 05/14/2001 Emissions/Computers/Electronics - Driveability Diagnosis
00-25-5 12/11/2000 Engine - Spark Knock During Heavy Acceleration
00T07 09/01/2000 PCM - Incorrect Calibration Strategy

As for the HVAC problem, this is indicative of a vacuum supply problem. The most likely problem is with the Vacuum Reservoir. This Vacuum Reservoir stores vacuum and,along with a check valve, prevents exactly what you describe on acceleration or heavy engine load.

The check valve is between the Vacuum Reservoir and the intake manifold. It is also possible when the engine work was done, a vacuum hose(s) was attached wrong or left hanging. The Vacuum Reservoir may also be cracked or broken or the check valve is bad or installed backwards.

As for the flashing lights, if they are door operated lights, one of the door switches may be bad or a door is out of adjustment.

Ford Windstar Breaking Spark Plugs

Additional Information provided courtesy of ALLDATA

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