Ok, one day my ZC (completely stock) just started to make a horrendous noise on startup, completely random, no new parts added or anything, a loud rattle/knocking sound, but it would dissapear if I went above 2krpms or once the motor warmed up.
After doing some searches and trying some stuff I've come to believe its piston slap. Its not a bearing or rod or the valves, but it acts odd. In all the posts I read about piston slap nobody ever mentioned a rough idle, it was just noise. Well I have a teribble idle, but once it warms up it purrs and is quiet as hell.

Most people experience it one cold startups, mine does too but it does it every day, on schedule when I leave for work (11am) but when I leave my 1st job theres no noise ever (5pm) then when I leave my 2nd job (11pm), its dark out, sometimes theres frost etc on my car so it should do it right? Nope, no noise at all, runs perfectly normal. Its only in the morning....so I thought maybe moisture in dizzy? Nope, today it was 70, with only 25% humidity, I left the cap off and let it air out b4 starting it this morning and rattle rattle rattle. It sounds bad from the timing belt area, maybe just 1 piston then?

My main concern is the rough idle, the tach jumps but not in tune with the motor, but the motor does hesitate and act like it wants to stall cometimes. I didnt hear anything mentioned about a terrible idle in every post I read about piston slap so I'm left driving around and not letting the rpms get below 2 grand on the way to work every day. Am I just s.o.l. until I hone and replace the rings? Bleh....stupid random ****, I appreciate anybody who reads all of this.

 

bump.

 

ROD BERING SLIPPED BRO....but if not, just to double check......change the oil and see if there is n e glistering stuff in the oil.......if there is the bering is gone.....the slapping could be the done because the piston if loose from the crank itself...check....hope this helps