I have an '04 Accord ex, 4-cyl, 5-manual with 68,000 miles on it, which I purchased new. It is my first Honda, and I have babied it. All maintenance is done as prescribed for severe service, even though I doubt I fall into that category. I have not red-lined the engine, ever, (perhaps I should?) and my typical mix of driving is 60/40 highway/city. My worst tank of gas was 27 mpg (Shell only), with an average around 29 mpg in the Winter, and 32 mpg in the Summer (I live in the Northeast). For the past 20,000 miles or so I've been changing the oil myself with pennzoil platinum 5w-20 and a purolator pure-one filter every 5k. Before that it was Kendall Gt-1 syn-blend 5w-20 every 5k.

I think the car is terrific, and I plan to hold onto it for a very long time, hopefully past 200,000k miles. However....

During the late Fall, Winter, and early Spring when the temperatures fall consistently below 40 degrees I get an annoying, "knocking", on cold start-up. It sounds very much like a diesel when under light load, 2-3k rpm. Typically it lasts 8-12 minutes depending on the ambient temperature, well beyond the time it takes for the coolant to warm. Although I can't say exactly, my best guess is I first noticed it around 15,000 miles.

Based on the research I've done I suspect, "piston knock". It is not a tapping or ticking noise. I had valve tappets on a '92 mazda protege, so I know that sound. I highly doubt rod-knock, given the maintenance history, and the fact that the sound goes away over time, and is non existent in warmer weather.

I'm curious, does anyone else have a similar sound from their k-series motor; could it be fairly common of Honda engines in general? I've lived ~53,000 miles with it so I'm confident the sound does not foretell imminent mechanical demise, but does it affect long term reliability?

It is an annoyance I've begrudgingly tolerated. For a vehicle that appears in every respect so meticulously engineered it is an issue that strikes a discordant note.

 

Issue?...

it's what pistons do when then have clearance in the cylinders. Due to the fact that the liners are made from different material than the pistons are made from the contract and expand at different rates.

The skirts are lightly tapping the liners, let the car warm up adequately and your fine

 

So, then, this is normal, or within the mechanical tolerances of this engine?

 

Commonly referred to as piston slap it is normal to some degree.

 

right, but piston slap is more known for happening in engines with forged pistons and larger wall clearances of like 0.004+"

I am pretty sure honda's use cast and it should be closer tolerances (like new 0.0008-0.0016", service limit 0.002" ) .

What it could be to is VTC actuator pin not locking properly .
I have to say it does sound like piston slap as the VTC would be quiet once oil pressure equals out in the VTC chambers .

 

It's normal and nothing to worry about and if it's been doing it for over 50k miles it's definately not a rod knock. It would've spun a bearing by now. If that's annoying you, you should hear piston slap on a stock sleeve motor with forged pistons when it's super cold out and the car isn't warmed up.

 

When VTC actuator makes noise it is only for a few seconds, not 8 -12 minutes. Piston slap is not exclusive to forged pistons.

 

Yes, you should. Constantly babying the engine isn't always the best treatment. A modern gasoline engine is designed to be run throughout a wide range of loads and RPM - you should beat on it a little bit every once in a while to keep everything cleared out. I see a lot of EGR clogging issues on engines that don't get revved up very often.

Normal. Without hearing an audio clip to prove otherwise to me, I can almost guarantee you that it's valvetrain noise. Have you tried any different oils (i.e. Castrol Syntec 5W-20 or Mobil 1 5W-20) to see if the noise changes?

Don't worry about it. It's good that you take care of your car (most people don't), but you're being just a bit too meticulous.

 

That's why I said it wouldn't be VTC cause he hears it to long of time and I still say its not normal for 15k engine (stock) to start piston slap , if it was made in tolerance .
Maybe if it was 70K + I could see it more .

 

thanks for taking the time to clarify the issue for me, guys. I appreciate it. I'll live with it, and yes, I'll red-line it on occasion when traffic is clear. Really, the car is great save for this niggling issue and I plan to keep it a long time.

thanks again.