I've got a '95 sol si w/ a z6. The engine makes a strange knock on cold startups that has me puzzled. It seems to last for around 10 to 20 seconds. Seems like the knocking noise is much slower than the rpms. Also seems like it is one cylinder that is doing this. It was my understanding that piston slap would take a minute or so to go away. My theory is that a rocker arm or two might have a lot of wear and would be rocking back and forth on the rocker shaft. I've been told that it takes some time for oil to get to the top end. Does this sound plausible? If so, how would one identify this instead of piston pin noise? Thanks for your time.

 

bump

 

first explain about what do u mean by cold start. how cold does it get where u live and did this noise start just recently after the season just change

 

I'm in the Detroit area, so it gets pretty cold. This has been going on for the two years that I've owned the car. This typically only happens when I first start the car in the morning. After the initial start of the day, I don't usually hear anything like the knocking. There has always been an odd vibration or noise above 3k that i've always noticed. A local tuner said it runs fine and didn't notice anything. Thanks for your help.

 

its probably cause the oil isn't up to the lifters and what not yet...just my 2 cents, there is some new oil that will protect you engine on start-ups too, Castrol makes it i think

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by no_one_ &raquo;</TD></TR><TR><TD CLASS="quote"> This typically only happens when I first start the car in the morning. After the initial start of the day, I don't usually hear anything like the knocking. </TD></TR></TABLE>

I have the EXACT same problem with my car. Once I drive it down the street for 30 seconds, it goes away and stays gone pretty much all day until it sits overnight.

My symptoms are: Rough idle on first start of the day & a knock under load until the engine warms up.......

 

Same problem here, too, in my girlfirend's 94 Civic DX... When the weather gets cold at night, say, down around 50 or below, car knocks under load, but not at idle.

I started a thread in the Tech section about it, and someone attributed it to piston slap.

I'm really not sure what the long-term effects of piston slap are, or if it'll blow the motor or anything... I just make her start the car and let it warm up before she drives it, just to minimize any chances of damage...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_EJ8 &raquo;</TD></TR><TR><TD CLASS="quote"> I just make her start the car and let it warm up before she drives it, just to minimize any chances of damage...

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thats what u are suppose to do when it gets cold. hell it happens to me here in sunny san diego when it starts to get cold (50-60 degrees) in the winter and fall

 

iT HAPPENED TO ME TOO!!!
majority of people told me that it's rod knock, need new bearings
sum people told me that it's piston slap..

i dunno what it is already...

hope sumone knows

 

personally i think its the rocker arms making that noise until theres good oil pressure in the head