1999 Ford Expedition spark plug question

Hi! Could you help us a little by trying to describe the problem? ( I realise that your information will be 2nd hand, but anything will be better than nothing).

Simon H

I think there's some missing going on and the mechanic thinks spark isn't getting to the combustion chamber. He said there is a "coil or some manner of electrical resistance" piece in the plug wire (they call it 'gume tubing') that needs replacment. I say bolluks; he should check the plug and plug wire because there may be any number of issues there, namely a faulty plug and/or wire . However, as we're dealing with foreign techs, I am taking nothing for granted.

Thanks.

What is the mileage?

I too doubt that this would be the problem unless they were messed with. I would tend to say TUNE-UP or compressi>I think there's some missing going on and the mechanic thinks spark isn't

The ignition wire may be the culprit then. I'll go to a parts store to see if I can get a hold of one.

Thanks for your help.

"FerruzAXP" wrote in message news:UOS2f.14196$Tn5.7603@trnddc08...

Expedition 5.4L engines all use "Coil On Plug" (COP) ignition. There is an individual coil for each plug. The coils are powered by the PCM to fire the plugs at the correct time. First generation 5.4L Expeditions (97-02 models) are notorious for having one or more of these coil packs fail sometime in the first 100,000 miles. Ford issued a TSB on this subject because a large percentage of the coils returned for diagnosis were not actually defective. However, the Ford recommended coil diagnostic procedure is so long and complicated, just replacing the coil is cheaper. If you have a misfire, the PCM error code will identify the failing cylinder. The mechanics could just replace this coil pack. It is also possible that only the spark plug has failed. Or it is possible that the connection between the coil pack and the spark plug has failed. Although the coil pack sits above the spark plug, there is still a "wire" connecting them. This is generally referred to as the spark plug boot. It can be replaced separately. It is really just a short spark plug wire. Whenever I have my plugs replaced, I ask that all the plug boots be replaced as well. They are relatively cheap. However, if there is a failure, I would not just replace the boot. In order to avoid going back to replace another part later, if I had one cylinder misfiring, I'd replace the plug, plug boot, and coil on that cylinder. If the truck has high mileage (more than 60,000 miles), I recommend that you replace all the plugs and plug boots (but not the coil packs -except for the bad cylinder). On Expeditions with 5.4L engines, it is usually one of the rear coils that fails (#3, #4, #7, #8). They are difficult to access. I believe they fail because of poor air flow, leading to the coil overheating, or degradation of the plug boot. It is often claimed that a leaking heater hose over the #4 cylinder can lead to coil failure. Ford uses quick connect fitting on the heater hoses at the firewall and sometimes they leak slightly, particularly if they have been disconnected for some reason (like changing the spark plugs). Your mechanic you be sure these hoses are properly attached. Many mechanics replace the Ford quick connect fittings with a traditional clamp. BE VERY SURE THAT WHOEVER REPLACES THE SPARK PLUGS, TORQUES THEM PROPERLY!!!!. This is very important. If the plug are over-torqued you can damage the heads. If the plug are under-torqued they may back out and damage the heads.

See:

Ed White

I guess the idea of "Coil On Plug" ignition is to eliminate the long run of plug wire with high voltage on it- instead they run low voltage, high current thru the long wire, and step it up to the high voltage, low current right at the spark plugs.

-Paul