i just bought a honda civic 4 dr ex. it has 130 thousand miles, on it, and the timing chain has not been replaced yet. i suspect the spark plugs might be fowled. i have a cold air intake, with a new filter, and a cat-back exhaust. i took the car to buddy of mine and he has one of those OBDII diagnostics tools that tells you throttle positon, coolant temp, etc, and he said everythin was fine. when i take off sometimes, and let the clutch out, the car hops, and its only when the engine is cold. the other day i checked the oil, and i was 2.8 quarts low and im not leaking any oil, but i dont think i am burning any either. when i go to the back and have my dad rev the engine, all that comes out is clear exhaust, until he is heavy on the gas and a sightly black smoke will come out, but no blue smoke. please help if you have any suggestions of what to do. i am praying that it is my timing chain and when i get that replaced, everything will magically be fixed. but would a bad timing chain cause bad gas mileage? also, i us shell regular 87 gas, and once a month i use the fuel injector cleaner.

 

well your mileage could be that bad if you lead foot it everywhere!

but go ahead and replace the spark plugs/ spark plug wires/ distributor cap and button.
and just check the old plugs for any that are fouled out more than the others. but 2-3quarts low sounds like either burn en or leaking the oil pretty bad...
and check the timing as well. and then replace the timing belt.

 

Its very hard on your motor to race it on a cold engine. When metal is cold the tollerances are different then when it is hot. Let it warm up, then have fun with it... Do all that addiction said, and change your air filter too. Then see how your gas milage is.

 

Tire pressure is a big factor too, as well as your O2 sensors.

Might be a good idea to get that timing belt changed ASAP. It's not what's causing your mileage problem, but you're going to have more then a gas problem if it slips a tooth or two.

 

$20 says your O2 sensor isn't reading correctly.

 

This major oil leak is the most pressing issue.

 

the only thing is that there is no oil leak on the cement but which o2 sensor should i try replacing?

 

This major leak threatens to destroy your engine. You must be losing oil when you are driving the car.

The primary oxygen sensor (before the catalytic converter in the exhaust manifold) is the one SovXietday is referring to.