M62TU Dreaded cyl 7 misfire

[bcredliner]

Originally Posted by upallnight

I would verify that you have spark at the plug and an injector pulse at the injector and go from there.

Since the missing is limited to cylinder 7 troubleshooting should focused on potential causes that could only result in one cylinder malfunctioning.

I also agree a leak down test should eliminate internal causes if the plug and injector current are good.

Welcome!

[Efiftythree]

So I have fixed the problem. Turned out to be the usual culprits, all at once.
Having replaced the CCV (which was completely 'chooched', as Ave would say),
I then double checked the electrics. I'd already replaced the injector but hadn't confirmed I had injector pulse. Multimeter confirmed I had both steady injector pulse and power to the coil.
When I first replaced the leaky valve covers, I purchased a new coil as I was pretty confident the old one on cyl 7 may have fouled due to the oil in the spark plug well. When I first swapped it out, it made no difference.
This time, with the new CCV unit, it worked. Misfire gone. Car runs smooth again.

So in conclusion, the valve cover gaskets began to weep at the same time as the CCV deteriorated, the pool of oil stuffed the coil (and probably the plug) and until I'd fixed the vacuum leak, the misfire would not disappear.

What a bastard to get that CCV out too. I'm amazed I didn't drop those little torx bolts down the back of the engine...

Thanks for your suggestions. Appreciate the help.

[upallnight]

If you had mentioned that when you replaced the spark plug with a new spark plug that the spark plug hole was filled with oil, someone would have pointed out to you that the oil in the spark plug tube is a known source for an engine to misfire.

[Efiftythree]

Originally Posted by upallnight

If you had mentioned that when you replaced the spark plug with a new spark plug that the spark plug hole was filled with oil, someone would have pointed out to you that the oil in the spark plug tube is a known source for an engine to misfire.

I'm well aware of this. Perhaps I should clarify the steps I took.
When the misfire became apparent, I went ahead and ordered a new coil as I was fairly confident this would be the issue but was too busy at the time to look at it.

When I finally had the spare time to change the coil, I removed the covers only to find oil in the plug wells. It was then I realised the valve cover gaskets were leaking
So I replaced them, along with 8 new spark plugs, having sucked the oil out and cleaned the wells, of course. I also installed the replacement coil.
After a full day's labour, the misfire still persisted on cyl 7.
Now I'm sure you can appreciate my frustration as logically it should have fixed the problem.

So the issue turned out to be the above, along with the CCV. For some bizarre reason, the new coil wouldn't fire (despite having power to it) until I replaced the CCV.
Or perhaps it was more likely the fuel shut off to the injector.. Who knows..

Glad the X5 is out of the way. I now have to sort out the intermittent jake brake on my Signature Cummins. Out comes the multimeter again...Yay..

[bcredliner]

The reason for intermittent problems is to expand our ability to calmly handle frustration. Side benefit of DIY.

[Efiftythree]

Originally Posted by bcredliner

The reason for intermittent problems is to expand our ability to calmly handle frustration. Side benefit of DIY.

Indeed. One of the joys of being a farmer. Always something in the workshop to fix.

[Purplecty]

I am experiencing the exact same issue here. Swapped in a spare used Bremi coil (can't confirm it was good so may try another one) spark plugs were stated to be replace by the PO but I will check those as well. Cylinder 7 is still misfiring randomly but no check engine light. I am watching the cylinder smoothness values through INPA. I ordered a new Kayser CCV and a Febi OSV and will probably do an intake reseal at the same time of the replacement...

https://www.dropbox.com/s/fs3w4xfh0u...53330.mp4?dl=0

[wpoll]

Do you have to clear error codes once the DME shuts down a cylinder due to misfire?

[andrewwynn]

yes. The engine will be in limp home mode until reset. You don't need to even shut off the car if you have a wifi dobgle in the obd port.


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[Purplecty]

I have not gotten an engine light or a stored misfire code sonce clearing but I can feel it...