Help with identifying engine noise

[Jocko]

I stand corrected, but I have only ever come across it in older, worn engines.

[culzean]

I stand corrected, but I have only ever come across it in older, worn engines.

This is a quote from a Toyota website....they claim the noise is not piston slap,  but its a slapping noise made by the pistons LOL.  My GD jazzes used to slap a bit in cold weather,  but only till engine warmed up,  can't really comment on my wifes GE as I don't often drive it without her  in the car and she always has radio on pretty loud.


A Note About Piston Slap: 'Piston slap' refers to the sound of a piston slapping into the side of a cylinder wall, and generally speaking piston slap is bad because it can lead to cylinder wall scuffing, ring wear, increased oil use, etc.

Many brand-new vehicles use short-skirt piston designs in concert with very high engine tolerances, and the designers are trying to minimize friction loses while maximizing efficiency. However, a consequence of these design choices is that some new engines make quite a bit of noise during cold start-up. This noise is caused by a very small discrepancy between cylinder bore diameter and piston-ring diameter. Commonly (and incorrectly) referred to as piston slap, this noise at cold start is in fact just a normal consequence of using a short-skirt piston in a cylinder with a very small margin for error.

[Jocko]

Researching further from that article it would appear that the "cold start noise" afflicts engines with aluminium forged performance pistons that do not contain Silicon. I don't know it the pistons in the Jazz are of that type, but it would appear that it normally disappears after about 30 - 60 seconds, but can last for up to 5 minutes on extremely cold days.
pg will be able to tell us if that is the case with his engine.
Does anyone else among us suffer from "cold start noise"?

[pg]

This might be an interesting point: The noise is there in the morning / evening when the outside temperature is around 12C and remains noticeable even after a few minutes driving (I have not tested yet how long it takes for it to disappear by driving alone). Yet when the outside temperature rises to 20C the noise almost disappears even as the engine is cold. This makes me think that it can't be directly linked to the engine as I would imagine the noise should disappear quite quickly if all it takes is 8C temperature difference?

[Jocko]

Pistons would warm up 8°C in a couple of seconds. Whatever the problem is it is interesting. Best bet is to let your garage have a listen. He may have a mechanics stethoscope, to help pinpoint or discount the noise.

[sparky Paul]

Piston slap get gradually quieter as the block warms up and the pistons expand. I wouldn't think initial temperature should make a lot of difference.

As for the noise, I think you need to be there to hear it really. A garage should be able to tell piston slap, it's a fairly distinctive sound.

[pg]

Still waiting for the appointment with the local repair shop but in the meantime I managed to get hold of the Honda dealer that last serviced the car in July before we bought it. They said that they had detected back then that the engine was misfiring and needed 4 new rear coil packs plus the 8 spark plugs. I'll check tonight if they have been replaced but thought of mentioning it here anyway. Would surprise me though if this was the source of the problem as I would imagine this is not something that gets better with temperature?

[Jocko]

Cars always run better when they are warm. Seldom get a car that won't start when warm. Usually happens, in the morning, when the engine is cold.
If you have to replace the coil packs get Hitachi ones. They get the best press. And be aware, though they look the same the fronts and rears are different, and not interchangeable.

[guest5079]

I bought a stethoscope as illustrated by Jocko off Ebay it has been invaluable over time in identifying noises.
I know one member did not rate them BUT they are a useful tool for the few quid it cost, it has helped with problems. I hasten to say I haven't had to use it on the Honda.

[Jocko]

I used to use the long screwdriver to just below the ear. I think the mechanics stethoscope was a later idea.

[sparky Paul]

Same here, long screwdriver on the bone behind the ear, squeeze the ear canal shut with the handle. Served me well for 30-odd years.

This is a lot shot, is pre-detonation (pinking) from loss of spark at the back bank of plugs a possibility? I know the two plugs fire sequentially, so maybe... I don't know. Pinking can be affected by intake air temperature... but should definitely be worse under load.