sorry to bring up an old post, but i think i may have put the wrong plugs in.

I am having some tranny shudder and ruff idol after changing out my plugs.

I have a 2000' model and the majority of the spark plug guides show OE gap for this car at .044"? Is that not correct for this model?

Or, is it in fact .8mm (?inches)? I will check my owners manual this evening and see what it says.

 

I just double checked my owner's manual and for my model (2000), it says to use the Denso SK20R11 (.043" gap) plug or the NGK IFR6A11 (.043" gap) plug.

 

Sorry for bringing up an old post. I just purchased NGK Iridium IX Plugs (.044") for my 96 LS, and looking at the manual it states to use a .043" gap



So are you guys saying I should use a .8mm gap instead of the 1.1 on a 96? I'm confused with the previous posts on this thread.

Also should I decrease the gap down .001 to match the manual specifications if my new plugs are .044? I'm new to working on cars. Thanks!

 

You are fine to leave the manufacturers gap as is. I've not been able to attain .001" precision so I don't try. You'll likely find that attempting to gap them each plug will result in more differences, this is near negligible for the usual commuter.

 

Denso is an OEM supplier to Toyota/Lexus
I located this Spark Plug Gap Chart on their website;

www.globaldenso.com/cgi-bin/global/plug/usa/4w/plug.cgi?name=LS400&filename=4w-37.txt&action=search





Earlier in this post it was suggested 1995 and 1996 LS400 require a shorter spark plug gap...
Anyone care to field this one?

 

Toyota has changed the design in August 1996 to use spark plugs that have the gap of 1.0-1.1mm (0.0394-0.0433in)
Below is from a JDM manual. It indicates the limit 1.3mm (0.0512in).

 

The required gap depends on the compression ratio, air fuel ratio, coil voltage and spark plug temperature. A bigger gap can only make a bigger spark if there is enough voltage to cause a spark under all these conditions, so a bigger gap may create no spark at all under some conditions. But, if the gap is too small, the plug is easier to faul. So, you should follow the instructions and purchase proper temperature spark plugs and properly adjust the gap.

 

No. You should not adjust the gap in case of a plug for LS400.
http://www.globaldenso.com/en/produc...ium/qa_22.html

 

Thanks Yamae.

It appears that one should not adjust the gap on iridium spark plugs, as this will damage them.