Was driving on highway all the sudden slowed down to 25 mph. Random misfire all cylinders. Checked plugs all coils and injectors are working properly. What could this be?

 

I bet you only think you checked everything. Did you just look at them? Did you probe each for resistance, blah, blah, blah...


How old are the plugs? Were all 8 replaced last time?


I had this happen on a 2006 (exactly the same as yours). It was very abrupt and out of the blue. Blinking CEL with active misfires, P0300, P030X (all 4).


8 new NGK plugs fixed it. Spendy at $14 each, but I'm pretty sure they were the original plugs at 220K miles.


After that, there was a faint stumble that didn't happen all the time. It turned out to be a single coil pack. I had a second 2006 at the time and swapped coils one at a time until the problem moved. $45 dollars from Rockauto for the Hitachi OE style coil and done - about $175 with tax and shipping when all was said and done.

 

I mean i checked all the plugs and they all have a strong spark. It had two bad coils. I replaced them and then on the test drive i went about fifteen miles before this happened. So for about first fifteen miles it will be ok and then it gets sluggish.. Are ngk the Oe plugs? Do you think it has to be ngk?

 

What do you mean, "strong spark"? Did you measure it in some way to confirm strong vs. weak? Did you do it with the engine and plugs at their operating temperature? Did you monitor it to make sure it never misfired?


Seeing that a cold plug has spark tells you nothing other than it has spark for the brief time you observed it. As temperature increases, electrical conductivity decreases. If the plug has high resistance, or the coil is weak, it gets worse as they heat up.


Again, you are describing exactly what my car was doing. It was fine until it warmed up, and it would go to utter crap.


NGK and Denso. Yes. It has to be them. They're the $14 versions at your typical parts store.


Did you buy stock or compatible coils, or did you buy the cheap sets off eBay?


These are among the most fuel efficient engines around, and they are very sensitive to small changes. You don't need to pay dealer prices, but you can't cheap out and expect good results.


If you want a fix, replace the plugs with NGK or Denso OE versions and replace coils with the Hitachi coils (Hitachi makes them for Honda).

 

Thanks Keith. I took your advice and replaced all plugs with denso iridum i got them for 8 a piece here in baltimore with my shop price. Not too bad. The coils I used when I had to replace where hitachi so I believe that is OEM. So since I replaced the plugs I think Im good. Took it for a little drive and about seven minutes in I had the check engine light flash at me. Cylinder 1 and 3 misfire. The scanner was plugged in the whole time I was driving. A couple seconds later the light went off and it has been driving like a champ ever snce. So I believe my issue is resolved. Thanks again.

 

I haven't checked in a while. The prices have come down.


the correct plugs are:


DENSO 3433 {#SK20HPRL11}
NGK 4458 {#ILFR6J11K}


Pricing is closer to $9.


Glad it's sorted. not sure why they're so weird that way. Everything is fine until everything is NOT fine.


Are you sure the replaced coils were actually bad?