Noisy engine in cold weather.
 

I just know someone will have the answer to this question. So how come my engine gets noisy in cold weather, as in fuel delivery, detonation clatter, or "cackle" , etc. It quiets down at highway speeds (60-75), but when slowed down in town or starting from stops, etc. it hammers away in there. It has done it since new and has 83,000 on her, so it must not be damaging anything. Absolutely no bearing noise or piston slap, nor wrist pin noise. Whaddayathink?

thanks
Bill in KY :D

Re: Noisy engine in cold weather.
 

A lot of people report their PSD gets noisier in the cold. I tend to believe that it's due in part to the engine oil, those people that run synthetic oil (5W-xx) or 10W-30 don't seem to have the cold-weather clatter nearly as bad.

I also think it might be due to fuel ignition being delayed, either by crummy lower-cetane winter fuel and/or other cold related factors. I say that because the rattling is similar to what I've sometimes experienced in the summer after I've bought some sub-par, low-cetane fuel. Using higher cetane fuel or an additive might help. I have found that running 20% or more biodiesel fuel really helps a lot, quiets it right down.

The third thing it might be is that cold fuel holds a lot more dissolved air than warm fuel does. That's true of any liquid, like a warm beer or coke goes flat right away. The increased rattle might be due to more dissolved air being present in the fuel when it's cold.