Code p0351, Ignition Coil

Hey folks,

I've got a few issues with my 99 escort 2.0L, but this seems to be the most pressing at the moment. A few days ago, my car ran rough and lost significant power while driving home(and continues to run this way, undrivable really). I couldn't go above 50mph. I pulled the p0351 code which states, "Ignition Coil A Primary/Secondary Circuit". I can't really spend alot of money on parts that don't *really* need replaced, so am hoping to track the problem down better.First, could spark-plugs and wires cause this(seems that would cause a missfire code instead perhaps?). I did just replace the spark-plugs(didn't help), but not wires. Should I try this?

I'm testing the coil pack according to the instructions given by the repair manual, which start out as:1. Turn the ignition key OFF .
2. Unplug the vehicle harness connector from the coil pack.
3. Measure the power supply to the coil by using a high impedance Digital Volt Ohm Meter (DVOM). Measure the voltage
between IGN Start/Run terminal at the harness connector and ground.
4. The voltage reading should be 10 volts.
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.
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Am I to understand this as saying there should be 10 volts at the coil pack when the car is off? If so, I'm not getting it. I get nothing with it off. If I turn the car to 'on' and measure, the voltage seems unstable(my tester will bounce around alot, never settling on a number), though it seems to briefly stop around battery voltage(12.5v). Either way, I'm not getting 10v. Is this a problem? I don't see how power could be the issue since the car does run, just badly. I also can't find any blown fuses or bad wiring which the book said to look for, though I may not be looking in the right spots if this is wrong. The rest of the checks on the coil pack are fine according to the instructions. Any ideas? Also, I understand that the coil pack has two coils in it, since I'm repeatedly getting p0351, does this indicate that it is that single first coil within that coil pack(well, that associated circuit), or that coil pack as a whole?

Any help you can give would be greatly appreciated, Thanks :)

I would think you would get a steady voltage reading when you are checking the input voltage. Could be a bad ignition switch.

Yes I believe there are two coils in the pack (the same way the 2nd gen. Escorts are set-up), but if either one or both of them are bad (or going bad), the only cure is a new coil pack. I got a spare coil pack for my 92 the last time I went into a junkyard. At home I swapped it in place, and it worked - so I know I have a spare I consider to be good. I think it cost me $5, not sure since I bought several other things.

I also thing the voltage should be steady, but not having a 2nd gen. Escort I cant be sure.

Welcome to AF!

The ignition coil pack contains two separate coils. Each coil fires two sparkplugs at the same time, one on the compression stroke and one on the exhaust stroke. So, if one coil is bad you will get fire on only 2 cylinders. I believe (don't know for sure) that one coil fires cylinder 1 and 3, and the other coil fires cylinders 2 and 4. Pull ignition wires out of the coil pack while the engine is running to determine if it is only running on 2 cylinders. If this is the case, then the coil is bad and should be replaced. Don't pull the wires at the plugs, you will get shocked. The ignition switch is supposed to be on to check the voltage at the connectors. If you have more than 75,000 miles on the ignition wires you should go ahead and replace them. oem Autolites are good.

Thanks for the replies, was quite helpful.

I started poking around all the wires again and found a wire loose under the dash leading to the steering column. There were two thicker black wires in a connector, with a thin wire connected off one of the thicker wires. That thin wire was loose, and popped off when I brushed over it. No idea if that was the cause or not(not sure what the wires were to even), but I'm measuring steady voltage now, around 12v.

I started the car(almost didn't start), and tried pulling the ignition wires on that first coil. The car didn't seem to run any different with those two pulled, so I replaced the coil pack. I've ran the car about 15 miles today, and so far the problem hasn't shown again; I think that fixed it.

Thanks again! :)

Well, after about 150 miles since replacing that coil, the problem came back. Was driving down the highway and suddenly had very little power. As I turned off the highway, the car died. Wasn't too far from home so I drove it back, it was running as bad as before. According to the code reader, I have the same code, too.

Could the wire on the steering column be loose again?

Nope, it's still connected.

The center wire in the coil connector supplies battery voltage to the coil and comes from the ignition switch, that's probably not your problem. The two outer wires in the connector supply pulsed ground from the PCM. The coil is split internally with one side firing cylinders 1 and 4, and the other half fires 2 and 3. Carefully tug on each of the outer wires close to the coil connector. The stranded wire inside the insulation is probably just hanging on by a thread. The harness is actually too short and gets stretched when you accellerate. Post your findings.

Thanks. Sure enough, that wire was damaged(it is still attached tho). I guess I didn't look well enough at it the first time. Not sure I have time to fix it today, but I'll post back once I see if that solves the problem.

On a side note: I realized I left the keys in and ignition to on all night, so my battery is completely dead; it's charging now, hehe.

You might have to go to Radio Shack to get the tiny female spade connectors, (eliminate the factory coil connector). Solder each of the new terminals on with a pigtail long enough to allow for engine movement. Then slide a piece of heat shrink tubing over each wire so it doesn't short out. Be careful not to mix up where each of the wires go on the coil ;)