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Discussion Starter #1
1. Are the specs on Denso 3421 (SK20HR11) iridium spark plugs the same as the specs on Honda OEM plugs for the MT 2000 Insight?
I had new plugs installed by mechanic and car seems to be misfiring along with MPG now 30-50 (was 50-80mpg). I thought that could be the cause. I believe I have the "B" type cylinder head.

2. Are all 3 heads the same letter, or can you have a "A" and say 2 "B" on the same car?

3. Is there any documentation on how to properly index these plugs?

Thanks.
 

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If you buy the correct stamped plugs, they will automatically be indexed.

If you're trying to index non OEM plugs, the open end of the electrode is supposed to point at the non-VTEC intake valve.

I am not sure if there can be different letters on the same head. I imagine there can be, but I've never seen or heard of it personally.
 

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Hmmm

I did my own research and used the IKH20 Denso Iridiums.

Here is my link to when I changed out my plugs and I did not index them. So far no loss in mileage but my "butt dyno" seems to have picked up quite a perk in acceleration.

http://www.insightcentral.net/forums/modifications-technical-issues/19576-egr-valve-trick-new-iridium-spark-plugs-new-brakes-maintenance.html

I plan on trying to do a 3 run pull on stock (used) OME B plugs versus my Denso Iridiums that I have in there now. But that will have to wait for a while...
 

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Discussion Starter #4
So with the correct stamped plugs there is nothing special that needs to be done regarding the installation, other than the torque?

Thanks for the responses!
 

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So with the correct stamped plugs there is nothing special that needs to be done regarding the installation, other than the torque?

Thanks for the responses!
That is correct.
 

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Discussion Starter #7
Well they switched out the plugs for OEM required "B" type but the MPG has not improved. I am at a loss as to what has caused this sudden problem. Perhaps the plugs need "braking in" or the extreme heat we have is causing it???
 

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Plugs don't need break-in. In fact, they will perform best immediately after being put in, before any deposits develop.

Heat should help with MPG, unless you're using the A/C?
 
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