spark plug and fuel efficiency question

[dionx]

I just changed the spark plugs on my 2000 Accord after 106,000 miles. I noticed one of them looked like it was burnt, and the chamber that surrounded it looked burnt while the other 3 spark plugs and chambers looked relatively clean, especially the chamber. does that mean that one spark plug wasn't working and was effectively running on just 3 cylinders? or would i have gotten a Check Engine warning if the spark plug wasn't working?

i just took a trip from Vegas and my average fuel consumption was about 25 miles/gallon. would i have better fuel efficiency if my spark plugs were all working?

 

[Zenmervolt]

If one plug wasn't firing, you'd absolutely know it. The car would vibrate like a washing machine with a single brick in it on high-speed spin cycle.

The plug was firing. As far as "burnt", that doesn't tell us much of anything. What you likely saw was a mild case of carbon fouling which is nothing really to worry about. ( http://wwww.procarcare.com/includes/con...cecenter/encyclopedia/ch07/7Fig12.html ) A "burnt" plug is typically used to describe one that melted.

For better pictures see here: http://www.autohausaz.com/html/spark-plugs_spark-plug-wires.html

ZV

 

[RCN]

Damn....and I spent the time to scan the back of a haynes manual........
http://img222.imageshack.us/img222/7563/plugs7mh.jpg

 

[rezinn]

You can lose a cylinder in an inline engine and not know it, because it doesn't unbalance the engine like losing one in a V engine. You'd definitely notice it while driving, though.

 

[dionx]

thanks for the replies. i never felt unbalance, but ive felt times where the engine would hesistate.

 

[FelixDeCat]

Assuming you bought this car new, you are saying that you havent changed them in six years with 106k miles on them? :shocked:

If this was a four banger you should have averaged at least 29-30mpg highway. Heck even my Mercedes gets that.

Ive seen twenty gazillion plugs on five gazillion cars, and the worst are oil fouled, resistor stretched almost 60 degrees or burned off. If you have a bad or fouled plug your engine would knock alot or misfire kind of like when you get bad gas (aka rough idle). You might want to replace your plug wires while your at it, because they do degrade over time.

 

[Zenmervolt]

Originally posted by: rezinn
You can lose a cylinder in an inline engine and not know it, because it doesn't unbalance the engine like losing one in a V engine.

Not in a four cylinder. It screws with the power pulses and causes a vibration that is very noticeable, even at idle. Actually, you notice it more at idle than you would at speed.

ZV

 

[alfa147x]

Lets go to the park.

 

[dionx]

Originally posted by: FelixDeKat
Assuming you bought this car new, you are saying that you havent changed them in six years with 106k miles on them? :shocked:

If this was a four banger you should have averaged at least 29-30mpg highway. Heck even my Mercedes gets that.

Ive seen twenty gazillion plugs on five gazillion cars, and the worst are oil fouled, resistor stretched almost 60 degrees or burned off. If you have a bad or fouled plug your engine would knock alot or misfire kind of like when you get bad gas (aka rough idle). You might want to replace your plug wires while your at it, because they do degrade over time.

well my honda manual suggests that spark plugs be replaced every 105,000 miles. but since i learned how to do them myself and spark plugs are relatively cheap, i'll change them sooner from now on.

 

[DurocShark]

Get the injectors cleaned.