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With five plus years and 28,000 miles on my 3.7 Roadster I was concerned about the state of spark plugs, particularly corrosion of threads due to water ingress into the deep tunnels they live in. GDI engines seem to suffered from this, often badly. Whilst checking it seemed good policy to change them to the latest spec. Laser Iridium ones offered by NGK.



Research suggested LTR6DI-8 (96588) are the ones and used with success by Mustang owners in the USA. I bought mine from the Green Spark Plug company. The same ones are also recommended for GDI Plus 4 engines. With individual coil packs replacement is easy following disconnection of trigger after sliding out white catch. A single 8mm head bolt secures the coil pack into plug tunnel. Once bolt is removed a twisting and pulling action will release coil pack assembly, although some resist more than others. A smear of silicon grease on waterproof seals will make the job easier next time although with a life span of 80,000 - 100,000 miles I don't expect to be doing this job again. The taper seat plugs are removed and replaced easily with a smear of copper slip on the threads. Thankfully they all came out as new with no signs of corrosion, possibly helped by the 30° angle of heads. A ⅝" or 16mm plug socket with extension does the job and replacements are torqued to 12ftlb. All very easy until you realise the right hand bank plugs are inaccessible until upper inlet manifold is removed!



See image but the manifold is held in place with seven bolts, a row of four towards centre of V and another three further out from centre. I chose to remove manifold with throttle body attached so first unclipped air box cover then released inlet hose clip to throttle body. The large diameter hose can then be eased off. The throttle body connector has a red tab which needs to be pulled out first and this can then be unpluged. Purge valve hose and electrical connector are also easily removed by squeezing tabs on former and pushing release tab on latter.



The outer part of manifold has just one mechanical support (see bracket bottom centre) underneath involving a horizontal 6mm nut and bolt through lug on underside of manifold. These fixings need to be removed. To the left is a hose also associated with the EVAP system and it's hose clip needs to be loosened. The front and back of manifold have those plug in plastic clips with integral cable clip supporting cabling. They both need to be pulled out. The rear one below the K14 label in first image refused to budge for me though and broke off. It was glued back on after re-assembly.

After the afore mentioned seven bolts are then released with the same 8mm socket noting that they are all captive apart from central long one at top of manifold. The loosened EVAP hose to rear needs to be eased off and there is a very short breather hose towards the front underneath which should just pull off manifold stub. It should then be possible to ease off the whole manifold assembly.

The remaining plugs are then easily accessed as before. Replacement of manifold is the reverse of removal although a new gasket, FEL-PRO MS97214 (available from States in a matter of days) is an option given the importance of an air tight seal. No sealant required though. The seven bolts need to be tightened in the sequence shown and torqued to 10NM.



Note it's suggested a vacuum cleaner in plug tunnels may be a good idea for removing possible debris but beware with inlet manifold removed any cylinder with open inlet valves will attempt to suck any protective rag into engine - don't ask how I know