Hi, I changed my spark plugs to the NGK, Iridium ones as recommended. On firing up the car, it was very rough and did not idle correctly. CEL came on. Any ideas? My car has only done 15000 miles and only decided to change the sparks due to time. Many thanks.

 

Coil pack not installed correctly?

 

I might be teaching you to suck eggs but new plugs need to be torqued up correctly to crush the sealing washer, might be worth checking one isn't loose.

 

Can you be more specific please? It looked OK from outside. Is it possible to fit the coil pack off centre?

 

Used a torque wrench so I hoped it was OK @ 25Nm.

 

One of the coil pack clips could be loose.

 

They lok snug... How would one tell of a defective spark plug - I guess that is possible?

 

The different gap / electrode size can sometimes highlight a coilpak that was on it's way out. There have been a few times (not with the Honda) where I've chagned plugs only to have to replace my coil packs soon after.

Having said that I also fitted a plug that had a hairline crack in it once - I wasn't able to see it until it had some dirt rubbed in it but that caused a nice intermittent misfire too - the type of one that comes and goes and makes you question your sanity !!

 

I take it no engine damage will occur unless something has broken off the spark plug - again would seem unlikely but...

 

If you get a code reader it should tell you which cylinder is misfiring