2000 Ford Focus ZX3 - Rough idle and no power - P0300 P0301 P0303 P0351 P0352

Abstract

My 2000 Ford Focus ZX3 has numerous DTCs. Clearly from the listed DTCs, this poor car was having some ignition problems. Although common for this make/model of car, the root cause of this issue was unexpected, from my point of view. The unexpected nature of the root cause of the issue caused me to make several mistakes.

Description

My Marine son was taking his little sister to teach her how to drive at the local high school. It was beginning to slightly rain so moisture was in the air. Right when my daughter took over the wheel, the car bucked, stuttered, and died. My son tried to restart it, but he was unsuccessful.

He called me to inform me of the car issue. I was very surprised, since up to that point, the Focus was very reliable and solid.

Waiting for the rain to stop, the next day I packed up my diagnostic gear and headed to the high school parking lot. I first tried to start it in hopes that I could drive it home to make it easier to work on. It started, but there was definitely a huge miss occurring. The car had no power and idled horribly. So, I then pulled the DTCs. Here's what I retrieved:

I figured that the misfire was caused by the ignition coil issue.

This car leveraged a coil pack with two coils in it that work in a waste spark configuration. In this configuration, spark plugs that are 180° apart are fired together. Since only one of them at a time will be on the power stroke, there are no problems.

Reviewing the wiring diagram for the coil revealed that it had three wires going to it:

I hooked up my two channel scope meter to ground and back probed pins 1 and 3 of the ignition coil. In KOER mode, I noticed that the PCM was definitely signaling the coil since it was bringing down the signal pins to charge up the primary coil and then releasing it to cause the primary coil to induce a current across the secondary windings that resulted in two spark plug arcs, causing the spark to ignite the Air/Fuel mixture in the appropriate cylinder beginning the power stroke.

I noticed that one cylinder seemed to be firing, but the other cylinder was not (the red circle highlights the cylinder not firing). So, I assumed the plug or plug wire was having an issue. As a result of this, I pulled the plug and plug wire and noticed no issues. I then decided to pull the coil, and the bottom of the coil had a big hole in it. I ordered new coil and installed it a day later.

After installing the new ignition coil, the car started right up, and I drove it home. But as I drove it home, I took a left turn, and the car stumbled for a second. I thought to myself that maybe now I have a transmission problem. I parked the car, and for some reason, I decided to start it again. It wouldn't start, and the Check Engine Light was illuminated. Great; Although, I didn't have enough time to fully diagnose the issue, I did pull the DTCs. To my amazement, I pulled: P0351 - Ignition Coil A Primary/Secondary Circuit Malfunction. What? I just fixed this issue. Dang it. Something is taking out my ignition coil. The probability of installing a bad Ignition Coil was low in my opinion.

That night I watched several    YouTube   FordTechMakuloco videos on the topic of ignitions. I decided to ask him what he thought my issue was. And you know what, he actually took the time to respond. That was so helpful of him. He said that this make/model of car had a propensity for the wire loom from the PCM to the coil to short to ground on the EGR pipe.

So, I knew I had to find a short in the Ignition Coil wire loom. I went through the shop manual to identify where all the connectors and wiring looms were in regards to the ignition coil.

The next day I opened the hood and performed a detailed visual inspection of the coil area. I did not want to touch anything in hopes that the issue was still occurring.    YouTube   ScannerDanner advises to look for wire looms that are exposed to movement and/or heat. So, with that knowledge, I knew the issue would NOT be wiring running along the firewall, since they never move. I knew it had to be something in the engine bay.

I found the issue. The wire loom containing the wires that controlled the ignition coil where firmly resting against the EGR tube. I pealed away the plastic covering, which was worn threw in one place, and found a wire completely exposed that was clearly touching the EGR tube. This wire was the control wire that matched the DTC error.

I took apart the wiring loom and inspected all wires to ensure they had uncorrupted insulation. Fortunately, only one wire was damaged. So, I cut out the bad section of wire out and soldered in a new section in. I used heat shrink tubing on both ends of the newly soldered sections. I then replaced the outside plastic protective wrapper and installed additional heat resistance tape. I used a wire tie to pull the loom away from the EGR tube. This was all done in an effort to prevent wires from touching and rubbing against the EGR tubing.

I installed a new coil, and the car is running like a champ.

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