skoobahead

1998 Grand Caravan, 3.3 ltr, 88,000 miles:
I have a slight knocking noise that can be heard with engine idleing. It's very obvious if I pull up next to a drive up window--the noise echos off the building. Car runs normally. Any one else experience this? It doesn't sound like a lifter and is pretty faint.

rodeo02

This sounds like what is referred to as "piston slap". This occurs when the pistons "rock" slightly as they move up/down in the cylinder bores. This is more of an annoyance than anything else & is not harmfull. In fact it's becoming WAY too common with today's engines (short piston skirts & low-tension rings) You can reduce & sometimes eliminate the noise by experimenting with different brands & weights of motor oils, or by doing a thorough de-carboning of the combustion chamber with sea-foam, dealer purchased de-carbing sprays, water mist with a spray bottle, or my personal favorites are at www.lubecontrol.com
G/luck
Joel

skoobahead

Thanks Joel,

Do you think you would still hear "piston slap" after the engine has warmed up though? In my case the noise is still there even after warm up.

John

rodeo02

Some engines only do it when cold (usually GM engines), some only when hot. I'd try a different oil & a good intake & combustion chamber decarboning.
G/luck
Joel