I pulled all of my plugs to read them and all of them looked the same except cylinders 7 and 8. They were notably cleaner than the others. See pics attached.

Compression on all cylinders was within spec. No unexplained coolant loss so I don't suspect a head gasket.

My question is: Are the rear cylinders leaner than the rest due to them being closest to the throttle body or are all of the cylinders balanced?

I'm trying to diagnose an intermittent stumble under part throttle acceleration. Since I see two "lean" plugs I'm wondering if I have an issue with the two rear injectors.

 

Here's another angle on the example of what the plugs from cylinders 1,2,3,4,5, and 6 looked like.

 

Sinister, No not all cylinders burn the same, I can say this from my ford mustang days. I owned a super charged mustang and during the build I was told to get balanced and flowed fuel injectors, I think it was Marren motorsport that was suggested. When I did receive them they were numbered as to which cylinder to place them in, due to the fact that some would burn leaner. I am new to the Jag motors, but I am sure they have cylinders that burn either rich or lean. Not by much though, nothing to worry about. Only if you are trying to build a race motor. Paul

 

Hi Paul,

Yep, I'm familiar with balanced and flowed injectors. Having spent many hours writing fuel and ignition maps for 3.0 liter V6 2 cycle engines that produced a minimum of 350 hp I've used lots of them.

Since I'm used to reading 2 cycle plugs, I'm real sensitive to subtle differences. (a lean cylinder is a recipe for a melt down)

In this case the difference was very apparent that the to rear plugs were the lean ones.

I'm wondering if that is typical for this particular engine.

Regards, Ken

 

Hello Everyone,
would you recommend the spark plug installation torque and if anti-seize on threads should be installed?

Thank you

<<<Mathew>>>