I've been reading a ton on spark plug gap and I'm getting conflicting info all over the place from here and other websites. Trying to come to some sort of conclusion on this. I have an 07 fit, 107k.

My car started shaking and hiccups once in a while at higher speeds so I figured I would look at my plugs and coil packs. based on everything I read here regarding their failures with no CEL I figured maybe it was misfiring.

One coil pack looked darker than the others but I left it in based on a resistance test I did and put in 4 new ngk iridium ix. They came gapped at .043 but I gapped them to .052. Manual says anywhere from .043 to .051. Ngks website stated OEM gap is .052. BTW, my existing plugs were denso iridium at .043.


So I Took it for a ride and it ran worse than before I put the new plugs in. wouldn't accel from high gear and just completely bogged down. Very herky jerky and shaking at high speed was also still there.

So then I put a new coil pack in to replace the dark one I saw thinking it has to be that one. Took it for a another drive, same result. So, then I ordered the remaining 3 coil packs, installed them and took it out again. This time it ran great, no accel issues at all but the shaking above 50 was still there.

My question is, is because it ran worse after the plug change but then better after the new coil packs, does that mean the gap was too large for the old coil packs to handle? And now the new ones are strong enough to accommodate for that large gap? Is that a possibility? Should i gap them back down? Will i shorten the life of the new packs running them this wide or it doesnt matter?

Thanks in advance for reading,

Sean

 

I lived with all these ignition problems for three years going through countless coil packs, spark plugs and valve adjustments. Everything I tried had very temporary “fixes” . Honda master mechanics couldn’t explain why these ignition problems kept coming back. Finally the car stalled completely nearly causing my wife to get T- boned in an intersection. This just got real ! I tried all the old temp fixes again, so frustrated.

Finally all I did was reduce the plug gap from .043 to .040 and I never had an ignition problem again. I couldn’t believe that something so simple could solve such a giant, accumulative expensive, life threatening problem.

Ruduce the plug gap, worked for me.

 

I was thinking of going to .047 which is right about in the middle. New coil packs should def. Be good with that. It's a nice middle ground between burning off clean between cycles and not stressing the coils over time.

If this has been an ongoing issue with so many fits what is the reason honda engineers set the gap so high from the factory? They had to do it for some reason.

Is there something specific to that particular oem iridium plug that runs better at .051 .052?