I have an 07 Fit with 113k miles.
Last year at 100k I changed the spark plugs after it started to hesitate while driving.
After a month I had two cylinder misfire codes thrown so I changed all the coil packs. Since then I've had a cylinder 2 misfire code on 3 different occasions, around every 3 to 4 months.
Each time I changed the coil pack and it works fine for a while.
This makes me think it's not the coil pack but I can't find any other option to persue.

Any ideas?

 

What are you setting your spark plug gaps to?
If over .045, that could be your problem.
Gregg

 

My random guesses:

Something loose in the wiring harness going to that coil pack?

Crud on the spark plug shell causing trouble?

Possibly a defective plug? Have you pulled the plug when you replace the coil pack to inspect it? Perhaps there's something else going on with that cylinder (valves or injector?) causing it to run rich or otherwise misbehave.

 

I agree check your spark plug gap; most will open with time and the wider the gap the greater the load on the coil. Apparently, since the trouble started after new plugs, its my first choice, too. Otherwise, Look at the voltage supplied to the coil; low voltage also puts greater loads on the coil.

 

The spark plugs were gapped at .45. I'll pull it and check. How much would it have to be off to cause a problem? If its not right on .45 but between .45 and .5 is it enough or would it have to get over .5 or .55? I'm not familiar with how much to tolerance is given.

 

I once changed the plugs on a V-6 Ford. Within weeks I started getting misfire codes. When talking to a dealership mechanic friend, the first thing he said was "You just changed the plugs didn't you?. Go back and gap the plugs EXACTLY the same in the center of the specification." I did that and never had another problem with that engine again.

I do not know how critical the gap is on a FIT but I would go back and gap those plugs again.

 

Good question; wish I had a definitive answer. We never did any kind of testing on the gap that varied horsepower but now wish we had.
However, you can be assured that the load on the coil increases with gap; the farther the spark has to jump the greater the need for higher voltage and that means higher current on the coils primary. So its important to keep the gap at or perhaps just slightly less than the specified gap. Try setting the gap to .040 rather than .044 and see what happens. Monitor the gap every 5000 miles to see whats happening there as well. Regap if necessary. . Your number 2 coil may be the lower end of the statistical limit of performance accepted by the manufacxturer, not Honda, so its particularly sensitive to the power that has to be drawn from the coil in order to jump the gap.

 

Back in the middle 1970's, GM came out with a HEI (High Energy Ignition). It eliminated points and developed much higher voltage at the plugs. Their original specification on spark plug gas was .080". Then they started having coil failures and in the late 1970s and dropped their recommended gap to .060". In the 1980's GM dropped their recommended gap to .040" with these same ignitions. What they found was anything over .035" made no difference in performance across all engines in their product lines (Buick, Chevy, Cadillac, Olds. Pontiac, GMC).

Based on that GM experience, I usually gap my plugs on the tight end of factory specs and make sure all plugs are gapped exactly the same. Most plug these days are platinum and will run 100,000 miles unless the vehicle has a high revolution per mile ratio. The plugs do erode the electrodes and the gap very slowly opens up over time. So starting on the the tight end allows the plug to remain in spec over a longer period of time.

 

Great stuff. I do remember the HEI but not the extra wide gaps. Higher voltage should mean wider gaps and the resulting spark length should ignite a larger sphere of the charge which of course should mean the air-fuel charge would fully burn faster and potentiaklly better so GM had the right idea. Perhaps it didn't work as well as predicted because that spark requires not only voltage but amps as well to get the strong spark needed to ignite the fuelk-air mixture. It was the reason for aftermarket ignition systems like MSI took command of higher power and compression engines.
I like the setting gaps at the lower end of the spec range and we'll use that here. Nice to see the coinfirmation that plug gaps do open with time and especiaslly the load.
cheers.

 

Even the high power after-market ignition system makers like MSD and JET (Jones Electronic Technology) don't get it right the first time, but their mistakes highlight the relationship between plug gap and coil voltage demands.

I installed a JET breakerless ignition system on my '87 Ford Bronco (when they still had distributors and one separate coil). The JET coil produced about three times the voltage of a stock coil, and heavy duty silicone-clad coil wire and plug wires were part of the kit. The suggested plug gap with this high power system was .058 compared to the stock gap of about .036.

The extra ignition voltage, and huge plug gap made a power difference that could be felt, and gas mileage went up by about 2 mpg. Everything was wonderful for about 5000 miles. Until------ the high coil output voltage burned the coil wire literally in two and the engine stopped dead on a blind curve in the mountains.

Expecting to get blown right off the road by a gravel truck slamming into the back of the Bronco, I was able to patch the coil wire pieces with tin foil as a conductor between the burned ends of the coil wire with silicone tape to hold it temporarily together, then drive it five miles back home.

JET would not admit that there was any problem with their design and would not replace any of the system parts, so I replaced that ignition system with one from MSD. The MSD system did not produce the extremes of coil voltages, but their coil was still much more powerful than a stock coil. I reduced plug gaps to the MSD (more narrow) recommendations, and never had ignition problems from then on.