Knock Sensor/O2 sensor/timing belt
 

Took my car to the shop today because the CEL was on. Anyway, diagnosis came back as:

1. Knock sensor not working
2. O2 sensor not working
3. timing belt

He quoted me approx $400 in repairs including labor. Which I don't think is too bad, but I'd rather not spend all that money right now.

From my research the Knock and O2 sensor basically manage my car's fuel efficiency, right? Am I doing long-term damage to my car by not replacing those two parts ASAP? Can I get away with it for a month or two?

I have to talk to the guy about the timing belt, he wasn't really clear if it needed to be replaced.

2003 Accord 4-cyl doesn't HAVE a timing belt (it's got a chain). I hope he's got a good story about that one. You might want to keep quiet about that until he tells his story, so you can judge his credibility in general.

Knock sensor & O2 sensor probably should be replaced. It's not just about efficiency; you could be causing other problems. Running rich can potentially ruin your cat.

sorry I misspoke. I meant to say "serpentine belt" (the one near the front on the passenger side of the engine), not timing belt.

My first thought was $400 was a good deal for a timing belt (if you had one). But now it sounds a bit high priced; OTOH I don't know what the parts would cost.