I picked up a 03 Civic Si a month ago. It has 60k on the odom. Only mod is a AEM V2 CAI. The engine sounds like I'm driving a diesel or it sounds like marbles in a can. It only happens when driving and during acceleration (light or heavy). It goes away after 10-15 min. of driving. If I stop and let the car sit for 10 mins or so, the noise is back and then goes away again(not as loud or as long as when first starting in the AM). My thoughts were Pre-ignition or valve chatter. I ran a few tank fulls of 93 oct and even added oct boost and no change. The oil was clean but it was overfilled by 3/4 of a quart (classic noise eliminator technique). I changed the oil with the right weight/grade and proper level and no change. Brought the car back to where I bought it and they said "what noise?" we didn't hear anything. Asked about the overfill and they said they didn't touch the oil. Now the the weather is cooler, the noise is louder and lasts a little longer so I'm going to bring it back one more time. I may have to bring them hearing aids.

Any thoughts would help? Thanks.

RAF

 

try setting the valve lash

 

Thanks for the reply. I drove a 02 SI w/45k on it this weekend. Bone stock. It has the same noise! Either its a coincidence and has the same problem or its an inherent noise on all 7th gen SIs.

 

My 03' at 30K does not have any. And my best guess would be valve clearance.