After reading how RT had his denso iridiums gapped to .050, I decided to stop being a wimp and re-gapped mine to .045 (my balls aren't as big as RT's ). Didn't have any problems, took a brief test drive around the neighborhood (~ 1 mile) and everything seemed fine.

Driving to work today (first real drive after re-gapping plugs) after about 15 miles or so of highway driving (including stop and go @@#%$$*^* beltway traffic), I noticed that if I accelerate hard, around 4k rpm it feels like it's missing. It's not real dramatic or anything, just hesitation and a reluctance to keep accelerating. It's fine if you don't push it - had the car up to 90+ mph (gradual acceleration) at one point earlier in my drive and didn't notice anything.

Does this sound like something related to the plugs? If I can find the right size allen wrench here at work, I will take the cover off and make sure the connectors to the coils are mated properly; anything else will have to wait until I get home.

What a pisser - car felt even smoother running with the larger gap

 

Should not be the gap, but you are right.. always have to suspect the last change when things go south. Look at each plug to make sure the electrode was not damaged (the iridium plugs look very fragile), check the wires and contacts. ..and buy a set of metric hex sockets when you get a chance.

 

Rocket, the one thing I was worried about when I opened the gap up was if the seal around the insulator was going to handle the higher voltage or break down. In an effort to avoid this problem I applied a liberal amount of dielectric grease to the boot prior to installing the coils. I don't know if this is really necessary since I didn't try it without, but you know.
This problem is a common thing on Miata's however, so it's not a bad place to start, if you got the balls to leave it large .

 

Honestly sounds like a fouled plug. Debri or oil could have gotten on the electrode. If that's the case then I'd just replace it. Two strokes and high RPM four strokes are notorious for it. Don't try to clean it. This will generally make it worst. Just replace them.

 

went back to .040 gap and no problems anymore

plugs looked fine when I pulled them out, so I have no idea what's up with the behaviour at the larger gap.

One thing that occured to me: I don't remember what the plugs looked like out of the box, but is the top part (anode?) supposed to be completely over the electrode? In other words, if I turn the plug up-side down (from the way it goes in the car) and look at it from the top, should the electrode be hidden from view by the anode?

Right now, if I look at the plug like this, I can see about 1/2 to 1/3 of the electrode peeking out past the anode. I am thinking that maybe when I gapped the plugs originally to .040 that I moved the anode both up AND back. If the anode is supposed to be completely over the electrode, this could maybe explain the behaviour at a larger gap. As a matter of fact, the way it is now would be a larger actual gap than measured with the feeler guage.

 

[QUOTE]Originally posted by rocketman
[B] I am thinking that maybe when I gapped the plugs originally to .040 that I moved the anode both up AND back.