I have a '92 Civic VX with a stock D15Z1 engine with 125K miles on it. I bought the car brand new and ever since day one the #4 spark plug is always fouled out.
I've taking the car to two different Honda dealers several times and they said everything checks out fine. Could this be a bad fuel injector from the factory? The car runs and idles fine.

 

If the plug is fouled, it won't fire regularly, or won't fire at all. I'm pretty sure you'd notice this. [Backfiring]

I'd try adjusting the plug wire that goes to #4. I've seen a bad plug wire cause a cylinder to not fire. Just moving it, wiggling it will help sometimes. (It did on my friend's 350)

Hopefully this helps.

 

Poor fuel injector, valves, or gaskets... I wouldn't be to worried, try some fuel injector cleaner, and start using higher octane fuel.


[Modified by w00t!, 8:12 PM 3/11/2002]

 

I replaced the wires, and that didn't help. If I replace the injectors don't they have to be a matched set? I keep the valves adjusted every 15K like the service manual says to.

 

no, you can replace the injectors one at a time. I had injector problems on my 92 ex sedan. when the injector went, it ran like crap... like on 3 cylinders... which it was, come to think of it. new injectors run about $50-60 each. I got mine form mancheseter honda... but any online honda parts place is good. you might want to try this site for parts...

http://www.acuraautomotiveparts.net/


good luck.