Not supposed to gap iridium plugs.

 

it is OK to gap iridium plugs if they are not to spec, it just depends on which type of gapping tool you use. do NOT use the one that is a disc with a "ramp" going around the edge as this type can break off the iridium tip of the plug.

 

If you got the -11 plugs they should already be gapped to 1.1mm. I do regap generic ones very carefully. Never a problem.

I’d be surprised by how far off your -11 plugs were, but then I don’t use Densos and don’t plan to. Only NGK ignition products. IMO the best there is.

 

Who knows. Your tool could have been inaccurate. I never ever gap Denso Iridiums. No problems yet.

 

It sounds like your tool might have been innacurrate. Borrow another one or bring it to a shop and have them verify that your tool is correct.

It is true that you are not supposed to gap iridium plugs, at all, ever. I wonder if the metal can't withstand the stress of taking tools to them.

Did you disconnect the battery while replacing the plugs? If you did, then your ECU probably reset and your car hasn't readjusted yet. You would definitely have rough idle problems after resetting the ECU if your throttle body is dirty (common on this car).

 

Was you spark plug gapper made in China? I have one made in the USA and one in China and they both read different gaps on the same plug.

 

Was you spark plug gapper made in China? I have one made in the USA and one in China and they both read different gaps on the same plug.

I have a premium Lisle spark plug gapper & feeler gauge set and made in the USA, and I never had a problem with it. It wasn't a faulty gapper it was the faulty gap set from the manufacturer or could have been banged up in the shipment to Toyota, many reasons that it could have happened. My mistake was trusting the pre-set gap and not checking them myself before I put them in....Like I said when I pulled the plugs they all were gaped at .038 not .044 as spec....Enough said...Thanks all...My cars back to running fine!

 

Did you get Denso SK16R11 or IK16 spark plugs, which are supposed to be pre-gapped to 1.1mm (0.433")? I suppose you did... It is strange that they were all gapped to 0.038". They were probably not properly gapped at the Denso factory... Some other Denso spark plug models do come pre-gapped to 0.9mm (0.354").

 

IK16 spark plugs...What's the difference in the two, SK16R11?

 

Original standard plugs are Denso's Iridium Long-Life SK16R11 (φ 0.7 mm iridium alloy center electrode) with platinum coated ground electrode.
You can upgrade to Denso Iridium Power IK16 (φ 0.4 mm iridium alloy center electrode) with taper-cut U-groove ground electrode, or Denso Iridium Tough VK16 (φ 0.4 mm iridium alloy center electrode) with platinum tipped ground electrode... They're all (supposed to be) pre-gapped to 1.1 mm (0.0433"), as required.

http://www.globaldenso.com/en/products/aftermarket/plug/power/structure.html

http://www.globaldenso.com/en/products/aftermarket/plug/tough/structure.html

 

I did that and now I'm changing out the plugs. I bought a decent wire type gauge. I think I used that center electrode as a lever (with a wedge type gapper) to make sure the gap was perfect. Woops.

 

Denso Iridium TT and Platinum TT are in fact gapped slightly smaller at 0.040".

https://www.rockauto.com/en/catalog/toyota,2004,corolla,1.8l+l4,1432915,ignition,spark+plug,7212

It's part of their advanced efficient design.

https://www.denso.com/global/en/pro.../products-and-services/automotive-service-parts-and-accessories/plug/iridiumtt/

Do not change the gap on platinum, iridium or twin tip spark plugs, as the fine electrodes may get damaged.

http://www.denso-am.com/media/corporate-news/2018/20180315_f2_spark-plug-frequently-asked-questions/