badj

Hi,

Hoping someone with a bit of experience with these can help - I'm now scraping the bottom of the barrel for ideas.

I have an AJ engine'd Maverick (3.0 V6 24v) and Cylinder #6 isn't firing.

Even with the COP disconnected, it doesn't throw a code, but did have a flashing EML and P0306 (misfire cyl #6) when driven.

When I first checked, I moved the coil pack and the problem followed, so thought "easy, coil pack". When I fitted a new one, the issue stayed on #6, with rotating both the COP and Plug with its neighbour (#5).

If you disconnect the #6 coil pack at idle (which is around 800-900 rpm) it makes no difference at all. The cylinder is doing nowt.

To keep it concise, this is what I have checked and found so far:

New Coil on Plug for that cylinder. New plugs (NGK Platinum) all round, and have also rotated and checked the motorcraft ones that were on it. Read the plug and it's quite dry - nothing that suggests anything other than a dry cylinder with no spark.

I've also checked with the COP in two different methods (ignition lead light attachment and also by arcing the plug outside of the engine). It's definitely sparking.

I stripped off the manifold and tested all the injectors, and they all seem fine - decent spray on them. I've also connected tested the injector manually (a bit bodgey DIY, but effective) whilst the rail is pressurised and it's definitely spraying a nice pattern into the inlet.





So, up to this point, I'm confident there is a spark and the injector is working, with fuel getting to and past it.

I used a long screwdriver and the injector is definitely ticking. I've also used a multimeter on the + pulse feed to the injector, and that is also working.

Again, with the engine idling and the COP both on and off, the plug doesn't seem to look wet. This is with both the old and the new plugs.


Moving to a compression test, cylinder #6 seems to be reading upto the 150psi mark, which is consistent with its neighbours.






I've also had a camera in the cylinder and nothing stands out as being unusual there either.

Crown:




Video scanning head/valves (bit poor quality)


I thought I saw something around 26 seconds in (and after), but I think it's just the light. Screenshot:





Any ideas? I'm completely stumped. It's literally this one cylinder.

mattxr3i

you have done everything i can think of!

Cracked head or valve seat that only makes itself known when hot and under extreme compression.....?

mattxr3i

ah, have you checked the valve is opening. Maybe a tappet has gone or a cam lobe....

badj

So, it turns out it was something moronic - from both the user and the manufacturer's side.

I bought the car like this, and it seemed to be only missing on Cyl #6, as per the photo below:




So I was browsing the USA based forums last night, and also on YouTube, where I noticed the COPs weren't connected in a logical way.

So I swapped round the connectors this morning, so the loom now looks cack handed...




...but it now runs sweet as a nut.

Apparently it's very common, and I've seen countless ones broken for parts or sold as spares online due to having a misfire on one or more front cylinders. Further reading suggests it's common for a garage (or "workshop") to do this without realising.

So the previous owner spent hundreds on it, sold it cheap, and I've spent a small amount (new COPs, plugs, spare injectors etc.) only for it to be something that simple.


Hopefully this might help someone out in future (or present)

mattxr3i

ha, glad it was something simple in the end. Enjoy!

gcfcos

Happy days