Cylinder #5 missing

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Feb 23, 2004 | 09:52 AM

bookem123

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Cylinder #5 missing

My 2000 F-150 starting running rough one day. I have a Next Generation Star Tester so I pulled the code. P0355, #5 COP malfunction. Replaced the coil. A few days later, same thing. Replaced the plug and the coil this time. A few weeks later, as of now, same problem. I noticed that the latest COP I replaced was a bit loose. Can this cause a failure? What is the torque spec for the COP mounting bolt? I've read horror stories about overtorquing and breaking these. What can be causing this repeated #5 COP failure???

Feb 23, 2004 | 01:10 PM

ranger88a

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Have you replaced the plug? Torque spec is about 12in.lbs.

Feb 23, 2004 | 01:38 PM

bookem123

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Well, I did not replace the plug when I first got the P0355 and replaced the first COP. But when I got the DTC again, I did replace the plug and the COP. (Even though the plug I removed did not look bad at all.) Now that I've gotten the P0355 again, I am really starting to wonder if something else is going on. Could the Engine Control Module have a bad output section? A coworker suggested that perhaps a bad capacitor on the ECM circuit board could be causing the coil to short out.

Feb 23, 2004 | 07:48 PM

ranger88a

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No, the pcm wouldn't cause the cop to short out. All the pcm really does is close the ground circuit for the coil to work. Check the wires to the coil closely and see if they are pulled back or not making good contact.

Feb 23, 2004 | 11:24 PM

speckk

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I had a similar problem tracing down what was blowing my Coils, it turns out that the Wiring was rubbing on the Accumulator bottle causing a short when the condensation would build up.

I wrapped the Wires and Strapped a Piece of Heater house around it. Fixed it

Feb 25, 2004 | 11:38 AM

bookem123

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Thanks for the info. I've replaced the coil and plug, again. This time I put dielectric grease in the connector, and I sprayed the outside of the connector with silicone based water repelling lube. So far she's running normal. Does anyone know if I can get the PCM coil driver circuit? My buddy here at work still thinks that a bad capacitor in that driver circuit could cause the signal to the coil to be a spike rather than a smoother signal, causing stress on the coil and eventually burning off the insulation between the primary and secondary within the coil. The failure mode for his scenario is the same as that for a wet or worn shorting condition, so unless I have the circuit, I cannot prove him wrong!!