2001 Galaxy 2.8v6 code P1364

[its-me]

Hi
Could somebody point me in the right direction. From cold start after about 3 miles the MIL light will come on and the fault code is always P1364. Last Monday the light came on after 3 miles I turned the light out and then proceeded to do 195 miles from Kent to Devon, the light never came on again, this included two stops for about 30 minutes each. The light then comes on the next day after cold  start after the obligatory 3 miles.
I have changed all 6 coils with genuine units, and have changed number 4 with another new coil, I have also replaced the coil multi plugs which were soldered and heat shrunk. The problem is always the same it comes on after 3 miles, I turn the light out and it never comes on again on the journey until the next cold start. The vehicle is a 2001 2.8 vr6 auto. Ignoring the light it doesn't seem to misfire or hesitate and returns reasonable fuel consumption.
The reason for changing the coils in the first place was that the plug seals on the cam cover had failed and the plug holes were filling up with engine oil, the previous owner had put silicone sealer round the coils and they were heavily contaminated with oil.
I am assuming it is a wiring fault, but why doesn't the light come on again on the same journey,it just does it from the first start up. Thanks in advance. Raymond

[insanitybeard]

It's a strange one to be sure, I'm assuming you changed the spark plugs as well as the coils? If you swap the coils round does the code still relate to a fault with cylinder 4? Like you say, if it's a wiring fault it's strange it keeps occurring under the same conditions and not randomly. The only other thing other than an ignition system fault that could cause misfire is low cylinder compression or spark plug fouling, but again, you'd expect to detect that misfire and it be more random in nature.

Other than that all I can think of is a problem with the PCM itself (powertrain control module) which is causing the recurring fault code, for this to be the case I'm assuming the PCM controls the ignition coil firing, not a separate ignition module, this will need somebody else to clarify if this is the case.

[Mirez]

95% sure the PCM does control the ignition on these, I would be looking at a wiring fault - it could be that the warming engine makes the insulation flex or something like that, I've had similar problems in the past where it's intermittent caused by thermal expansion.

[its-me]

Hi
I have now checked the fault codes with a Snap-on Solus and have two fault codes which are the P1364 and P1176.Previously I have used a smaller Snap-on code reader. When I went into it further with the diagnostic checks, basically it said there was a short or poor connection between the O2 sensor and No4 coil. Not having access to a wiring diagram, is it possible that the post-cat O2 sensor is causing the P1364 code to appear. I know when it was MOT'd he mentioned the cat was a bit lazy, but it met the emissions criteria. The car has done 144,000 miles so is it possible that the issue might be there ??. I have subsequently tried the fault codes again and the smaller code reader just picks the P1364 and the Solus P1364 and P1176,which also when doing further diagnostics high lights the connection between the post cat sensor and No4 coil.