What going on my fellow Civic junkies? I need your help! I've got a '97 Civic EX and for about a month or so I've been hearing this rattling noise under the hood everytime I start the car in the morning. The car starts fine but as soon as the engine starts running I hear this noise like a piece of metal is loose and is vibrating/knocking on something metallic in sync with the vibration of the engine running. As I accelerate the noise goes away but once I lift off the gas pedal it begins to rattle again. I also notice a reduction in the noise once I've been driving for a while and the car is warm. If the car is stagnant with engine running, and I turn the steering wheel... the noise reduces/goes away but may come back/increase again once I stop turning the wheel. Could it be a power steering issue?

My check engine light is on and the diagnostic showed that I need an O2 oxygen sensor. But I've been driving this car for about a year now without it and the check engine light only recently came on (3-4 wks ago). Is this a legit reason for the "check engine" light to be on? Any ideas are greatly appreciated! Thanks!

 

Really tinny rattling noise is usually one of the exhaust heat shields. Get under the car and shake stuff around to find it.

If it is the primary oxygen sensor you should replace it promptly. It's going to affect your gas mileage and performance and possibly burn out your catalytic converter. You can keep driving with the secondary oxygen sensor bad no problems unless you need to pass a smog test.

 

Pop the hood and have a buddy start the engine. Then, while standing over the engine, try to pinpoint the source of the noise.

 

Thanks for replying. The noise is actually pretty loud. Think it might still be that? I took it to a mechanic today and he said that my primary oxygen sensor was missing (based on where it usually should be). After driving it for a year or so, why do you think the oxygen sensor would only now come on these past 3 wks (if it really was the oxygen sensor)?

 

follow your exhaust from the motor to the cat there should be 2 o2's ..
do you see a hole where one is missing?