Bad OEM Spark Plugs (Ford)

[Mister Tee]

The 'splorer is pushing 100K and it had been starting hard in the cold weather recently.  Hard starting can be due to a lot of things, but it was due for new plugs.  I always had good luck with Iridium plugs, so I went to Auto Zone to get some.

Turns out they didn't have any Iridiums.  In fact, nobody appears to make Iridiums for that vehicle (which I learned after a trip to another auto supply place.)  I settled on some NGK platinum plugs.  The OEM plugs are copper.

But I got to thinking - copper plugs that are intended to last 100K?  My experience has always been that that there is no degredation in performance within the manufacturer's specified plug replacement interval.  So I pulled out the old plugs and put in the new ones.  Sure enough, the old plugs were pretty chewed up and were fouled on the tips, even though the bottom of the plug bodies was a white ash color indicating an otherwise normal lean running condition for that type of engine.  Basically the plugs were marginal from wear, and started to foul on cold starts from short trips.  New plugs solved the problem.

I was also dismayed that Ford would put a CDI style ignition with high tension wires on a new motor in this day and age.  The modular V8's since mid 90's have had modern coil over plug ignitions, why not this one.

[BlkBird]

Assuming your Exploder is relatively new ( Less than 15 yrs ) it would have Platinum or Iridium plugs as OE specified.  Most likely Platinum which has a life expectancy of about 60 thousand miles but will often last in excess of 100k.  Considering your comments about them I would guess they are Platinum.  The older copper core plugs are typically only good for 30 thousand miles.  As far as the coils, the central coil with wires is cheaper to maintain than the individual coils so as far as I am concerned I would count my blessings.  The newer systems that use individual coils for each cylinder are not cheap to replace when they go bad and now you have 6 or 8 of them instead of one.  Yes the wires do wear out but they typically last for around 100k and they aren't that expensive.  One recommendation, if you haven't done it recently I would highly recommend removing the throttle body and cleaning with throttle cleaner and a proper nylon brush, this more than anything will help a ton of driveability concerns, especially at your mileage.  If you have a MAF sensor I would also recommend cleaning that.  Glad you were able to identify and fix your hard start.

Dave

[Mister Tee]

It is less than five years old, and it in fact has OEM copper plugs specified.  The plugs I pulled out were, indeed copper.  Bosch and NGK both make platinum versions of the plug, and nobody I am aware of makes an iridium plug for it.  Maybe Denso might, I didn't have a cross reference for them.

I have always found COP (stick coil) ignition systems cheaper to maintain, simply because the stick coils have always lasted the life of the vehicle in every vehicle I've owned and there isn't anything else to go bad except the plugs themselves.  I'm sure I'll be replacing the high tension plug wiring before the next plug change, but who knows.

Thanks for the heads up on the MAF sensor, I'll probably give that a go next weekend.

[BlkBird]

In a properly maintained vehicle you are right that the coil-over ignition will typically last longer than the single coil design.  I typically see the high mileage vehicles that were not properly maintained and subsequently need multiple coils on the coil-over vehicles which cost more than a the single coil with wires.  Honestly most coils if the vehicle is maintained should last to around 200k or thereabouts.  Don't forget the throttle body, it has a much greater impact on your idle than the MAF will after cleaning.  It can be cleaned while on the vehicle but will be more effective if done off the vehicle.

Dave

[Leo]

Let me see if I have this straight, and I am not picking on anyone.   The Factory stuff lasted 100,000 miles with no worries.  Now it needs some maintenance, and the owner is unhappy with the design, parts specified and maintenence techniques?   Looking under the hood , (like 100,000 miles ago)  all that equipment was there.  It performed acceptably all that time.  I personally would be delighted.  Screw in a set of whatever plugs the book says it needs, and drive it.   It is a good vehicle!    I had a Pontiac in the family that needed an ignitor coil or two a year from the time it was two years old until it was traded at 6 years old.  It never got to 100,000 miles.


If it makes you feel better, my 97 Grand Marquis is still wearing the factory wires and the two factory coils at 125,000 miles.  It still gets 19 mpg around town and 25 plus on the highways while being smooth, quiet and comfortable. 

[T Cro ®]

..... I typically see the high mileage vehicles that were not properly maintained and subsequently need multiple coils on the coil-over vehicle.....

I'm curious what lack of maintenance would cause a COP to fail? 

[Outback_Jon]

If it makes you feel better, my 97 Grand Marquis is still wearing the factory wires and the two factory coils at 125,000 miles.  It still gets 19 mpg around town and 25 plus on the highways while being smooth, quiet and comfortable.

My 96 Sunfire went 247k (totaled in an accident) on the OEM wires and coils.  (Two coils, four wires, four plugs - seems like a familiar design...)  And it was only on it's second set of plugs.  I was just about to replace the plugs when the accident happened.  Car was still getting 32mpg.

[VirginiaJim]

Well, that's it then, isn't it?  Keeping plugs in beyond their stated life can cause accidents.  I'm changing mine today.

[Outback_Jon]

Well, that's it then, isn't it?  Keeping plugs in beyond their stated life can cause accidents.  I'm changing mine today.

I finally got around to changing the OEM plugs at around 140k, when the car was getting difficult to start in really cold temperatures.  I could literally measure the gaps with a ruler at that point.  0.125" is getting a bit large...

[jworth]

I just changed the plugs on my mother-in-law's '05 Mercury Monterey which is a van if you don't know.  Now that's a job that's overly complicated let me tell you.  You have to lie on the ground and reach up behind the motor to reach one of them, and that's not the greatest of the difficulties.  I digress.

That vehicle had factory coper plugs with a single coil.   It's got about 150k miles on it. The symptoms were stuttering under load and throwing a misfire (on #1 cylinder only) code. The coil tested good.  Upon inspection, the plugs were out of spec.  Gap measured .075 rather than the spec of .054".  Also, there was funny little metallic deposit right where the spark would probably hit the little tongue thing.  Anyway, trip to Wal-Mart at 10 pm on NY's Day scored me some plugs.  I was surprised that there were no fewer than 4 different plugs that they kept in stock to fit including an iridium plug if so desired.  I went with Bosch platinum.  All's well now plus I scored some brownie points

[Mister Tee]

Let me see if I have this straight, and I am not picking on anyone.   The Factory stuff lasted 100,000 miles with no worries.  Now it needs some maintenance, and the owner is unhappy with the design, parts specified and maintenence techniques?   Looking under the hood , (like 100,000 miles ago)  all that equipment was there.  It performed acceptably all that time.  I personally would be delighted.  Screw in a set of whatever plugs the book says it needs, and drive it.   It is a good vehicle!    I had a Pontiac in the family that needed an ignitor coil or two a year from the time it was two years old until it was traded at 6 years old.  It never got to 100,000 miles.


If it makes you feel better, my 97 Grand Marquis is still wearing the factory wires and the two factory coils at 125,000 miles.  It still gets 19 mpg around town and 25 plus on the highways while being smooth, quiet and comfortable.

Well, that isn't exactly true - the plugs didn't QUITE make it to 100,000, as there were some worries.  Don't get me wrong, I'm not completely unhappy with the design, it just contains features I consider antiquated given its age.  Otherwise it is quite functional, and overall it has been pretty reliable with only minor issues so far.

I have owned an older Toyota Corolla, which did have all the modern features I expect in an engine including OEM Iridium plugs, COP ignition, etc... and it was completely reliable for the 210,000 miles I drove it.  Plugs lasted the specified 120,000 miles with no issues, and it could take a thrashing.  I redlined it at every opportunity, shifted without the clutch, and just generally ragged it out but it held up like a champ (still had the original clutch at 210,000 miles even.)  I kind of use that as a benchmark.  I wouldn't be surprised if it's still in service pushing 400K or more.

[Strawboss]

Vehicles in Ohio rarely last more than 100,000 miles, not because of the motors but because of rust. Consider yourself quite lucky.

[BlkBird]

I'm curious what lack of maintenance would cause a COP to fail? 

When the gap gets larger than designed the coil has to "jump the gap" which causes higher amperage numbers than it was designed to deliver long term.  This will eventually cause the coil to overheat and fail.

[Cholla]

Some COP systems should not use platinun plugs because of the higher resistance.

[BlkBird]

Some COP systems should not use platinun plugs because of the higher resistance.

Very true... I only recommend OEM specified plugs unless you are building your own engine and need to a "hotter" plug.

[T Cro ®]

When the gap gets larger than designed the coil has to "jump the gap" which causes higher amperage numbers than it was designed to deliver long term.  This will eventually cause the coil to overheat and fail.

Makes sense....