I am looking at buying a 98 z28 m6 ls1 and have a few questions. The main thing is that there is a ticking sound coming from the motor, not very loud, but it is audible and you can tell it is a tick tick tick ...sound. The dealership told me that it had a bad motor in it but they didnt know what it was and how much it would be to fix it, the car was a trade in so the dealer didnt know about it. I am thinking that it is just piston slap, hopefully anyway, not a rod knocking. Can anyone give me advice on how to tell if it is a rod knocking or just piston slap?? Would there be a loss of power due to the rod knocking? How much would this be to get it fixed?? Any advice would be greatly appreciated. thanks.

 

If it's piston slap and it goes away after the car is warmed up there should be nothing to worry about. Mine's got a slight ticking noise (piston slap) when I first start it but it's gone after 3 minutes or so.

 

it have "check engine soon" light on? mine does the same ticking and its a knock sensor and bad spark plugs. if the car your looking at has ~100,000 miles bad spark plugs will mess it up

 

Could be some bent push rods making the ticking noise.