2003 Impala 3.4L 3400 W/159,000 miles has engine chatter.

[dalemetcalf]

Car has a bad chatter in engine valve train sometimes when driving about 20 miles or more. When car is turned off for about 10 min or morning start up there is no engine chatter. Oil & oil level is good, Engine is not running hot. What could be causing this problem?

[ProTech]

Sounds like you have a very common upper end noise. Pretty much every 3.4 during those years and every variety of that engine, develops a valvetrain noise with normal wear and tear and/or a lot of miles or lack of maintenance. Usually this noise is in the valve lifter area, but sometimes it can come from the rocker arms if they become loose/worn/broken.

This would require the intake manifold and associated parts to be removed if you plan to change the lifters, which is most likely your noise issue. Since it seems to come and go with driving it's probably an oiling issue getting to the lifters (the lifters not staying pumped up), so they would need replaced. Very, very common problem on those engines.

[dalemetcalf]

Thanks you for your answer to this problem. That's what I was planning on doing is replacing the hydraulic lifters and checking the rocker arm assembly for any worn or broken parts.

Thank you very much, for your certified ASAE mechanic information .