pL2009

I have a rattling noise under acceleration when cold. It's done it since I bought it in October with 95k on the odometer (2009, non-nav). 104k now. I've read quite a bit about the VTC actuator grind, but my impression from reading everyone's description of that issue is that it appears at cold start. Mine doesn't make any noise until I start driving. If I hadn't read about the VTC grind, I would say it sounds like loose heat shielding, but I can't find any, and once the motor warms up, the noise goes away.

I know it's impossible to diagnose a noise over the internet, but does my description trigger anything for anyone in terms of something I should look for or check into? Thanks.

EuroRspec

iTrader: (1)

If you live in the salt belt, it's most likely the heat shield. My brothers 2001 Integra had a similar issue where it would only rattle under acceleration when cold and would go away when warmed up. It turned to be the heat shield around the catalytic converter.

Get the car on the lift and inspect all the shielding around the exhaust and body.

pL2009

So apparently I'm an idiot. I think what I've been hearing for 6 months was engine knock. I finally decided to put premium in it and I haven't heard the noise since. I was actually completely shocked in retrospect as the noise went away from the moment I drove out of the gas station. I expected it to take some time for the gas to get through the lines and fuel injectors (although at the time I wasn't thinking about it because that's not why I put premium in it). Premium in Michigan is 93 octane, and I put almost 15 gallons in, so even with ~4 gallons of 87 in the tank, my guess is I'm running 91 octane at least. I'm wondering if I'll notice any further improvement as I put the 2nd, 3rd etc tanks of premium in.

I had read so many threads about regular vs premium when I bought the car, and I know that according to the owners manual, premium isn't required, only recommended, and that below 87 can harm the engine. I also the accord has a "detuned" version of basically the same motor that takes 87 (lower compression ratio however, which is key for octane requirements) so I assumed I could get away with regular, especially since I don't drive it hard. Apparently I was wrong.

I don't want to turn this thread into yet another regular vs premium thread, but for me it is noticeable. I know the arguments both ways. Why spend the money on premium if it doesn't affect anything? vs You bought a $30,000 luxury car and now you are being cheap on gas. I get it and I understand both arguments, but I've always leaned toward the why spend the money camp, as I don't think I've ever owned a car with engine knock, so I guess I wasn't sure what I was listening for. I can now say that when I've tried premium in previous cars I've owned, it definitely made no difference. This one clearly does, at least for my 09 4 cyl TSX. I haven't decided whether to see if I can get away with 89 octane or not. If I do, it's not about the money, only my own curiosity, but I'll probably stick with premium.

I also do understand that I'm only about 200 miles through my first tank of 93 octane, so if the noise comes back on premium, I'll keep this thread updated, but at this point I'd be really surprised since I've heard that noise every day for 6 months, and haven't heard it since I filled up last.

Like I said, I can't believe I didn't realize this sooner. What sort of engine damage have I likely done allowing it to knock for 6 months and 10,000 miles? Argh.

thoiboi

dang.. glide it all worked out and thanks for following up with the data point!

TSX1012m6

Anything other than 91 (or 93) is an option? I did not know that.

Also to comment on the rattle noise, although it sounds like you got it fixed, I also have noticed this. My VTC actuator was replaced under warranty (even though it still makes the noise from time to time on startup). The noise I have is regardless of outside weather, for the first few minutes of driving the car, anything over 2.5~3K introduces a rattle noise, which I am assuming is related to the VTC actuator. Even at times when the thermostat is reading operational temperature. It goes away after 5 minutes or so of warm up/driving time.

pL2009

I thought it was, but according to the owner's manual: "Your vehicle is designed to operate on premium unleaded gasoline with a pump octane number of 91 or higher. Use of a lower octane gasoline can cause occasional metallic knocking noises in the engine and will result in decreased engine performance. Use of a gasoline with a pump octane number less than 87 can lead to engine damage."

As I said, I read several threads on this subject before buying the car, and I guess I thought the language was more suggestive than this, but this language makes it clear that I'm an idiot.

I would have described the noise I was hearing as more of a rattle or a grind before I would have described it as a "metallic knocking" noise, but whatever. I hope that's what it was, and I will run premium from here on. Lesson learned. My noise (knocking I think) did get better as the engine warmed up, but never disappeared completely. I only noticed it under mild to heavy acceleration, again worst when the engine was cold, although I tend to go easy on the motor in general and especially before it's warm.

WheelMcCoy

Damage is likely to be negligible, unless you were accelerating the entire 10,000 miles.

ceb

As an engine ages, its need for higher octane increases - but - you'd have to do some pretty serious acceleration to regularly get engine knock and the knock would have been obvious as knock.