1GZ-FE spark plug change - pics included

[Norbie]

I've owned the Century for about 5 years now so this was long overdue: a new set of 12 spark plugs. I've noticed that power and fuel economy have gone south recently so I'm thinking (hoping) this is the cause. We'll see. But first, I need to pull half the engine apart, swap the plugs, and get the engine back together in the correct order. This is no easy feat with an engine bay so crowded with so many parts. It's a bit like working on a stock 2JZ-GTE, but you're dealing with two of them at the same time!

Anyway, yesterday I decided to man up and get cracking. Here's where I started, with my 12 Denso plugs (ordered from the US via eBay) laid out ready. Note I used iridium plugs; factory ones are platinum but they seem to be specific to the 1GZ so they're super hard to find, whereas the otherwise-identical iridium version is used on a billionty different Toyotas and can be bought anywhere. I've successfully used iridium plugs in my 2JZ for years so it should be all good.
(pic)

Airflow meters and associated inlet tubing removed:
(pic) (pic)

Upper plenums and throttle bodies removed:
(pic) (pic) (pic)

At this point I can see just one of the coils I need to remove, the rest are hidden under the plenum:
(pic)

Here's the underside of the throttle/upper plenum assembly. Notice how those runners are substantially narrower than they appear from the outside? It's clear Toyota went to a lot of effort to artificially restrict the power output of this engine.
(pic)

Passenger side plenum removed, exposing the coils and plugs. Note it's a weird hybrid of waste-spark and coil-on-plug; there are three coils sitting on top of the front three plugs, and each one is connected to one of the rear three plugs:
(pic) (pic)

The plenum. Nothing much of interest, except that the runners are quite flat, so their cross-sectional surface area is a lot smaller than it appears at first:
(pic)

The coil and plug wire assembly:
(pic) (pic)

Finally, the plugs - old vs new:
(pic) (pic) (pic)

The plugs have now been replaced and the coils/wires re-installed. The only difficulty I've had so far was fishing the plugs out of the plug tubes which are exceptionally deep on this engine, and my spark plug socket is missing the magic rubber bit which pulls the plug out after you've loosened it. I'm sure anyone who's worked on a 2JZ knows my pain, but it's even worse in this case.

That's it for now, I ran out of time and my legs were getting sore from leaning over that very wide engine bay. Next weekend I'll tackle the drivers side and hopefully get started on re-assembly, which is going to be by far the hardest part. There are so many little bits and pieces I can potentially forget about or re-assemble incorrectly, it will be a minor miracle if I actually get it right. I'll continue taking lots of photos as I pull everything apart so hopefully I'll be OK. Wish me luck!

[lexsmaz]

Looks like a fun Job !! i think i will stick to the 1 + 2 jz ..

Best way to get the spark plugs out once undone is just get a straight spark plug lead off a an old Falcon or the like & push it down over the loose plug & pull out via the plug lead the rubber boot on the lead will hold the plug in & you can also use it for refitting & you can even initially screw the plug in as well ..

Those coil packs from memory look very similar to the 1jzgte vvti coil packs ...

[rob]

hes alive.........

[roadkill]

Hi,

looking good so far. I should be getting my 1gz in the next week or two. Straight onto the engine stand to do this sort of thing to it. Then to find a car to put it into.....

bEn

[Hack]

Looks to me like you have a good case for individual throttle bodies

Hack

[Norbie]

ITB's on a 1GZ would be amazing. Someone with more time and money than me needs to do this, stat.