1991 Civic SI Hatchback
I have noticed in the past month or so a decrease in MPG, a slight loss of power and a muffled ticking sound. I finally got around to a basic tune up (oil change, new plugs, new filters.) As I was pulling the old plugs, I realized one plug was very loose. The entire plug was covered with black soot. I was definitely losing compression from around the plug and I'm afraid I may have some valve damage. Am I screwed? What should I do next? Any help and opinions would be greatly appreciated.

 

you should get a d16z6 or d16y8 vtec head or just get the whole engine.

 

SOHC heads can be pulled off in 20 minutes if you don't lollygag. D16y8 MLS headgaskets cost ~$26 from hondapartsdeals.com. Valves there aren't all that cheap, but you can always find someone with old ones or get them off ebay.

My guess is that the cylinder was intermittantly sparking, as the plug wouldn't have a good ground with soot all over, you're just lucky it didn't cause a fire from igniting the mixture outside of the cylinder.

 

From what im reading the ticking noise could have been one of two things.
first, if the plug was "very loose" the ticking could have been that cylinder igniting the fuel mixture. but if it was that loose it probably would have blown the plug wire off.
second, it might be some loose valves. check the lash and set to specs and see what happens.
and if your interested i have a z6 head and intake complete minus throttle body that i'll get rid of for 75 bucks.

 

Black soot means you are running rich. You could be running rich due to a bad O2 sensor. A bad O2 sensor will also cause a decrease in MPG. Just do a compression test on it before you go tearing it apart. ITs not hard and takes 10 minutes.

 

the black soot was probably because the plut was loose so it wasnt firing rite so fuel wasn't burnin??

 

thanks for all the help. compression checked out ok. i replaced the plugs and it seems to be running fine. ive ran a full tank of gas in the last 3 days and im getting 38mpg. almost back to its old self. thanks again...

 

38 mpg! BADASS! I dont get over 28 anymore...