knocking sound when idle

[karryss]

Is there anyone you guys have problem like this? went to Yosemite yesterday and while at the gate i've notice some kind of quick knocking sound at the same time looking at my rpm bounced down one line and up to normal but when put to P or N it's gone. any help pls. bought the 80 last month with 97,800 miles

 

[Rookie2]

From what I understand, some valve chatter is common for these motors, but piston knocking at idle is not normal. Listen some more and see if you can tell which one it is. The rpm's should not be oscillating under idle conditions. Is this hapening all the time, or have you just started noticing it? Possibly bad gas. Do some more listening and post back with more information about the frequency and conditions that it happens under. Your post is a little general. Try to be as specific as you can.


Rookie2