Local Tech diagnosis was a misfire on cylinders 6 & 8 (I have new coils and plug). It looks to me that the spark plugs cover is just a pop off cover (red arrow and X on the pic) - I was expecting bolts holding it.

Any tips for doing the job or anything to watch out for?. Looks to be a bit crowed at the rear of the bank.

Thanks - Mac.

 

It's all easy and straightforward and yes they're just plastic covers.

 

If the covers are the same design as on the XK, then they just pull straight off (the cover has two holes on the backside that are pushed down over metal pegs sticking out of the block).

 

Thanks guys - yes it was very straight forward - hardest part was pressing down on the release tabs to pull back the plugs off the coil. On the front and rear cylinders I had to use two universal joints. Plug colours look good - surprised by the amount of oil on the threads.

I can't say if replacing the coils improved the cold idle roughness as the ambient temps are high. I'll probably do the other bank of 4 later. Car is running great.

 

Definitely worth changing those plugs as you have them out anyway. Do you know what mileage they have done? They may well have been inserted with some grease on the threads. I always smear a little anti-seize grease on mine although some people say that the threads should be untreated but I have successfully ignored that advice for over 50 years. 👍

Richard

 

Depends on what plug kind one fits... e.g. NGK (iridiums) for my car already have anti-seize & NGK say not to use more.

 

I've never seen any evidence of any anti-seize compound on any plugs I have ever installed and the includes NGK Iridiums.

Their website says:NGK spark plugs feature trivalent plating. This silver or chrome-colored finish on the threads is designed to provide corrosion resistance against moisture and chemicals. The coating also acts as a release agent during spark plug removal. NGK spark plugs are installed at the factory dry, without lubrication or anti-seize.

Anti-seize can act as a lubricant, altering torque values up to 20 percent, increasing the risk of spark plug thread breakage and/or metal shell stretch. Thread breakage can sometimes involve removing the cylinder head for repair. Metal shell stretch changes the heat rating of the spark plug and can result in serious engine damage caused by pre-ignition. Do not use anti-seize or lubricant on NGK spark plugs. It is completely unnecessary and can be detrimental.

Of course, each of us must take a view as to whether we believe that some or all of that is dramatically over-stated for commercial purposes and act accordingly. 😉

Richard

 

Check your LTFT trims when you cold start, and see how they progress as you warm it up. Lots of old orings and seals in these that harden and shrink over many years. If your LTFTs starts high (say, towards 10, and reduces toward normal (zero) as the engine warms, run a smoke test and see what the vacuum seal status is.

Also, check the ground point off the coils to make sure it hasn't degraded. You can find it in the electrical manual, in the stickys.

Also, ask the mechanic how many misfires occurred. A few a week, while not precisely correct, is not a problem.

 

Thanks for the feedback guys - the car has 95,000 Km/s on it so I would think those are the original plugs (car had 78,000 Kms on it when I bought it) so I'm guessing they would have been installed without some sort of lubricant. I replaced all 4 with Denso Iridium 5303.

 

Looking at the pic seepage has gone past the compression washer. - all four showed similar to varying degrees.

 

Does that black hose going to the supercharger plenum just pull out?

 

Yes, just some wiggling needed (after the hose clamps are loosened up well)

 

Thx but i am talking about the smaller black hose looks lije a pcv hose that is plugged into the bigger air plenum.

 

Ok - just a bit fiddly to compress the two clips and pull out at the same time.My fingers aren't the best especially on that kind of design.

 

This hose here u pinch it

 

Got it thx for your help