This post describes changing the spark plugs on a 2.6 engine, which it is very similar to the 3.2. It can also be used as a guide when replacing spark plugs on 2.5/3.0 engines, though in this case there is a fair amount of additional items that need to be removed to gain access to the spark plugs.

More specifically, there are four main differences between the 2.5/3.0 and the 2.6/3.2 with regards to access to the spark plug area.

The first is that because the newer engines have individual coil packs, these are incorporated into the spark plug holder and there is not DIS module or HT leads. Instead, there is a plastic cover on top of the spark plugs (between the rocker covers) that needs to be removed.

The second and third is that with the newer engines being ‘Drive-by-Wire’ and having no mechanical EGR valve, there is basically nothing at all blocking access to the driver-side spark plugs, making it very easy to work on.

The fourth is that on the newer engines the idle speed is ECU-controlled thus no ICV unit, making access easier to the passenger-side spark plugs.

If working on 2.5/3.0, these items will need to be removed to improve access. Also, on the 2.5/3.0 you will need to mark the HT leads to ensure that each is returned to its original location. And last, the plug wells on the 2.5/3.0 are not covered as on the 2.6/3.2 and dirt and oil can therefore accumulate in them – the wells should be cleaned prior to the plugs removal and care must be taken not to allow dirt or foreign objects to fall into the combustion chambers.

Pic 5 – Passenger side – at the front of the engine, remove support bracket screw A. Open clip B and move the coolant hose out of the way (there is another clip in the rear of the engine that needs to be removed as well in order to free up the hose completely). Disconnect plugs C and D. Remove screw E (picture shown with screw already removed) and remove the bracket holding the air-condition pipe. Move the air-condition pipe as far away from the engine as possible - I found that sticking it behind the dipstick did the trick.

Pic 6 – Lift the tab at the base of the oil filler cap and remove the oil filler cap by turning it quarter-turn anti-clockwise. This is a good opportunity to check the condition of the cams and gear – assuming that the bit you can see is representative of the whole system – and mine is clean and shiny.

Pic 7&8 – Remove the brake servo vacuum joint by using two spanners, a 17mm on the bit that is screwed into the plenum and a 19mm on the outer unit. You need to keep the 17mm spanner steady and work only the 19mm, to make sure that you do not loosen the bit the goes into the plenum. Once removed, move the vacuum pipe out of the way.

Pic 15&16 – The infamous rear passenger side spark plug presented no problem whatsoever – it seems that on the new engines access is good, as long as you have the exact right length of extension. The pictures show that both a standard ratchet and a torque wrench can easily fit. However some find that removing the scuttle helps improve access.

Pic 17 – Interestingly, the spark plugs removed from the engine were branded Bosch, not Vauxhall or GM. The replacement ones are also made by Bosch but are GM-branded. Both have the same number stamped on the metal part so the old plugs and the new plugs are identical.

Looking at the old plugs, they did 40k and they seemed fine (the old plug in the picture seems a bit blackish but this is not the case – they did look right). Vauxhall’s specified replacement intervals are 40k for the 2-electrode plugs fitted on the 2.5/3.0 and 80k for the 4-electrode plugs fitted on the 2.6/3.2, but I think they should be replaced at 40k regardless.

Pic 18 – The old plugs removed from the engine clearly had copper grease applied to the threads, and since these were the original factory-fitted ones I followed suit with a thin smear of copper grease. However, some say that the spark plugs should be fitted dry, so make up tour own mind which is best for you. As I said, I chose the old-fashioned method and had the plug threads copper-greased.

Fitting the new plugs – good practice is to use a rubber hose to get the thread started in order not to cross-thread the spark plugs sockets. I didn’t use one – though  I don’t advise doing this – I screwed the spark plugs in by hand with a long extension, using VERY VERY little force, no more than what you can muster between your thumb and forefinger, and backing-up at the slight sign of resistance. With extreme care and a steady hand this can be done, but again this is not the recommend way.

The spark plugs were torqued with a torque wrench to 25NM. I also noticed that the wrench ‘broke’ exactly after 1/4 turn from pressure applying point – which is what it should do.

Pic 19 – refitting is basically just a matter of putting everything back as it was. As for the coil packs cover screws, I have no torque figures for them, and the only indication is that they were quite tight on removal. But the whole thing is made of plastic, and over-tightening the screw may fracture it and allow water in. So I tightened it as hard as I could using only a 3/8” screw-driver handle and a socket (instead of a wrench).

Pic 20 – All done… I started the engine, it ticks-over fine and no Engine Management Light on (meaning that all wires and plugs were in the right places).