So what's the correct spark plug gap?
 

Solved. My manual system used the maximum gap for used plugs - 1.4. New plugs are 1.1 according to TIS.

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Original Post:

Did my plugs today. Got genuine Toyota replacements from Lexus. I verified they were authentic.

The gap was strange. I always gap my plugs. Reading the ones I took out and the new ones out of the box they were the same but only at 1mm (.038in gap). Further, all the new plugs appeared to be pre-gapped at 1mm. My manual says it should be 1.4mm so I set them at 1.4mm (.055 in). The old plugs were at 70,000 miles and in great shape. Car feels like it has more power but it's probably just my imagination and/or that I had the battery out.

Anyway, I know how to gap iridiums (never press the tips) and set them right on at 1.4mm, but man, I am bothered that the old and new plug gaps matched before I re-gapped the new ones to the manual. I'm just not sure what the right gap is supposed to be. If I hadn't of bothered checking them, I would have put in plugs with the same gap and probably never noticed. Ugh.

The Denso FK20HBR11 come pre-gapped. The factory gap is set to Gap: .043" (1.1mm). In this day and age, I would not mess with a pre gapped plug.

Lou

I've gapped a ton of plugs, but I wouldn't even try to gap these plugs with their super tiny electrodes. Disaster waiting to happen without special (and expensive) tools.

Agreed..

Joe Z
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Yeah, that's all fine and good but what if some yahoo drops one and places it back in the box. You have to check them to be sure. We've read some of the threads here with those terrible smashed electrode pictures and somehow those cars ran. They aren't hard to gap. I used a pair of magnifying glasses and a simple spark plug gapping disc. (Yes, I used a micrometer to get it right). Just don't pry on the tips. They're spark plugs not quantum computers. Anyway, I'll keep everyone posted if my engine develops any weirdness. So far it feels a little more peppy and the same old wonderful Lexus smoothness. I mean at the end of the day is a 0.3 mm (0.006 in) difference- what is that, like, three atoms?! Lol.

Also, I am going to be calling the dealer service to ask one of their techs to look at their manuals for it. Or if someone here has the actual FSM, please let me know what it says.

Here's the recommended spec:

Jeff

Thanks Jeff. Do you know if that is from Lexus or a spark plug manufacturer?

That is from Lexus, though it is likely based on the tolerance given to them by the plug manufacturer Denso, a member of the Toyota group of companies.

Jeff

^^ Correct straight from Denso OE manufacture. :bigok:

So I have a question in to my on-line manual service (who uses the FSM's) about where they got their 1.4mm spec. I did settle with finding several high performance tuning sites that said you can increase gap in 0.005" increments until the engine misfires under full throttle, then back it off 0.005" and you are set at optimal spark gap. Since I am only a little over 0.005" over stock, and no misfires, I feel comfortable leaving it. I'll report back when I get a response from my manual service.

I'm not aware of any Toyota or Lexus engine that uses a gap that large. Definitely a mistake on the part of the manual supplier.

If you're not experiencing issues such as spark blow out, you're going to be fine.

Jeff

This shows up at WOT and high rpm. The likelihood of going over 150 mph to find this problem is pretty small.

Well, I made to 120 a few times times yesterday :-):driving:

Why bother with the OEM denso Long Life ...??

Just use the Iridium Twin Tip makes you "Go Faster"


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Joe Z