What can you tell from spark plug colour?

[PugwasHDJ80]

Just changed the plugs and coil packs on a Toyota landcruiser V8. Suspect the plugs are 20 years old and at least one cylinder was missing.

Can anyone identify the missing cylinder, or share any other tips from the photos of these plugs. Plug one is bottom left, plug 4 is top left, 5 is bottom right and 8 is top right.

[julianm]

Champion used to do a wallchart of plug colours & diagnosis - I see there is an updated version which might help you a bit: https://www.championautoparts.com/Parts-Matter/aut...

[rigga]

Second one up on the left (so cylinder 2?)

But with modern fuels its not like the old days reading plug deposits, spent many a time plug chopping a 2 stroke, still have one, but really needs a gas Sniffer on a dyno to really confirm mixture.

[GreenV8S]

Exhaust header temperatures can show cylinders which are dead or have a severe misfire - and that's probably more informative than looking at the plugs.

[E-bmw]

6 looks slightly less well "worn/used/heated" but none are 1,000,000 miles from where they should be.

[steveo3002]

2nd from bottom both sides look a little off...one is white the other slightly on the black side

nothing to worry about

[996TT02]

They all look within range for "OK". Guess the occasional misfire is not going to show up on deposits. Only permanently missing on that cylinder would.

[IAmTheWalrus]

Spark plugs are so cheap, I just replace them.

[Boosted LS1]

plug 5, bottom right has some wetness around it but not enough to diagnose as a cause of misfire. They've all been working. I'd change the plugs and certainly replace the leads as those could be shorting all over the place. Check them out in a dark garage with the engine running. Every spark you see is one that didn't make it to the plug.

[PaulKemp]

To check plug colour properly you should run it on the road or dyno under load and immediately switch off ignition at test speed stop engine and pull the plug.
The colour will change if you cruise home, idle car and then pull the plug

[steveo3002]

not sure you can a great deal from them anyway ..i have a banger that uses at least a litre of oil per 1000miles yet the plugs look text book great

[Polly Grigora]

Can see that 1 and 4 are red and the others are white or close to white

Being a gambler, money would be on there's something different happening inside cylinders 1 and 4 that shouldn't be

[Dogwatch]

As said, none look too bad. If you have changed plugs and coil packs is the misfire sill there? Probably not.

[littleredrooster]

PaulKemp said:

To check plug colour properly you should run it on the road or dyno under load and immediately switch off ignition at test speed stop engine and pull the plug.
The colour will change if you cruise home, idle car and then pull the plug

Exactly this ^ ^ The plug colour only tells you what was happening in the last 10 seconds of the engine running. Many happy years of doing plug chops on temperamental TRs/TDs/TZs!