CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Problem with # 1 coil

I have a 2006 Ford Focus, the # 1 coil has been replaced 2 times in the last week and a half. It doesn’t appear to be the coil that is the problem but so far nobody has been able to fix the problem. Any suggestions. The car is still with the mechanic.

Are the inputs to the coil within spec.? is there anything driving the coil to constantaly be at max output?

If your mechanic pulled the codes and PO301 is what came up:

From the factory shop manual for my 02 Sonata

PO301 Misfire detected in cylinder 1

Possible causes:

vacuum leak in air intake system = lean misfire.

Fauly ignition coil, plug wire or spark plug malfunction.

Low compression

Faulty fuel injector or fuel injector circuit malfunction.

Your mechanic should be working from a flow chart such as this. Is he?

As far as I’m concerned a coil should never be replaced without replacing the spark plugs.
Coil failures are often caused by subtle, and sometimes not so subtle, misfires of the spark plug.
I’m fully aware of those hokey factory recommendations about allowing spark plugs to remain in place until oblivion or a 100k miles+; not that there’s much difference in the two.

That’s also assuming there is no mechanical fault with the engine, etc. but I’m going on the assumption an '06 with average mileage is fault free.

" It doesn’t appear to be the coil that is the problem but so far nobody has been able to fix the problem."

So what exactly IS the problem?? You neglected to tell us that…If it’s misfire, have you changed the plugs??

This is what I got when I went looking for “ignition coil” at Auto Zone: an ignition coil adapter, “one required for each pair of coils”. http://findarticles.com/p/articles/mi_qa3828/is_200608/ai_n17187409/.
If a spark plug misfires, the ignition coil builds up a charge, the charge must dissipate somewhere. The only “somewhere” is through the body of the ignition coil, itself. Enough of these internal-to-anywhere-to-ground discharges will ruin the ignition coil.
The ignition system needs a thorough test and inspection.

Back in the old days, we would “put it on the 'scope” and WATCH the primary and secondary voltages for all the cylinders displayed on the screen. Any abnormalities stuck out like a sore thumb. Have those skills and techniques been lost??

I agree back in the old days a compression test and “scoping the engine” were done if the slightest bit of trouble was encountered when looking for the cause of a sympton.

I haven’t seen a working scope in many years but many of the higher end scanners have scope capabilities. Perhaps we are dealing with a lack of equipment or skills.

When a OP says “the car is with the mechanic” he could mean it is at the house next door and the guy that lives there works for JL. You just don’t know what people mean when they say the car is with a mechanic or seen by a mechanic,unfortunately people withold these type of details.