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2003 v6 3.0L Misfire PO351 PO301 (SOLVED) on Ford Escape

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Viewing 1-5 of 5 comments
I have read extensive posts throughout the internet about problems with misfires on the v6 3.0L DOHC engine. After reading extensive posts and watching numerous videos I decided to tackle the problem myself. Many posts referenced that they were being told by their mechanics/technicians that they needed to replace the COP (Coil on Plug). After removing the plenum twice and resealing it to access the #1 COP (that I was told was the problem) I replaced the crankshaft sensor, #1 COP and all the plugs. I was STILL getting a misfire and code.

I searched for posts where owners had replaced their COP's and were STILL having the issue with the #1 cylinder misfiring. I happened across one post where someone had resolved their issue by checking the wiring at the PCM (brain/computer) on the firewall. I removed the insulating tape and sleeve and began to wiggle each and every wire while the engine was running. Sure enough! The wire that is closest to the edge on the right side of the connector was indeed worn from apparent vibration and flex of the wiring harness. The insulation of the wire was intact, however most of the copper strands of wiring had been broken inside.

I removed the connector by loosening the bolt in the center and removing the four-pronged shield to expose all of the wires. I spread them apart and began to check each one for damage/wear. This was a bit tedious, but paid off in the end. I found the culprit.

This explained why my misfire was intermittent. When the wire was bent back upon itself, the cylinder would fire for a period of time and then stop. I stripped away the insulation of that specific wire. It is in the right hand side of the edge of the connector. It's colored green and white. Apparently because of the proximity to the edge and the constant flexing of the engine and harness, this wire had failed.

I had enough wire exiting the connector to strip the insulation and make a solder repair. I used a handheld solder iron and some heat shrink tubing to repair the broken wire. I then tested the engine before re-taping the wiring harness and bolting it back to the PCM. It idled as smooth as it once did.

After weeks of banging my head, unnecessary parts and even a broken plenum bolt I was ecstatic to resolve this issue. I would suggest checking the PCM connector wiring before you go to all the trouble and expense of pulling the plenum and replacing COP's. Pay close attention to the wires that are at the right edge of the connector. These seem to be most susceptible to stress. Flex them a bit and you will be able to tell if the wire inside is broken. Even if the insulation seems fine.

I hope your repair is as simple as mine could have been.

2003 Ford Escape - 3.0L V6 188,249 mi,
I had the same problem replaced the COP on number one cylinder. The problem was still there. I followed the lead on the Green & White wire coming out of the Computer Connector and found the wire broken. Soldered and heat shrunk the wire back together and it is smooth as a babies bottom again. Not only did it fix the misfire it also corrected the A/C problem I was having due to the computer cutting out the compressor for low power because of the Misfire on number one.

2003 Ford Escape - 3.0L V6 200,000 mi,
Cylinder 1 2 3 misfire changed coil and plug still reads same and missing

2003 Ford Escape - 3.0L V6 134,000 mi,
misfire on no 4 cylinder

2003 Ford Escape - 3.0L V6 148,000 mi,
Run poorly jerking no power, had computer idianosis done