knock when accelarating,idles rough

My 1999 venture 3.4 has been idling rough at stop lights,but when I take off it smooths out.it does not stall. Also over the last few days it periodicallyt has a knock when i accelerate? but not always? I ve changed the oil and the pcv valve,oil filter...any ideas??

We bought a 2003 new venture and have had the knocking sound ever since. They said it was normal and that it would not get louder. They were wrong. I did get louder, quite a bit louder, but they still could not decide what the problem was. On a hunch, they replaced the ball bearings. That created an additional squeal that they managed to repair and only lessoned the original knock on acceleration. Should you ever find a mechanic who knows what the actual problem is, please let us know!

We got a 1998 Venture used but from the time we got that it did that. The dealership said that was normal took it to the shop ended up being the lifters. , which area lot of money!

my 98 does it too. I just live with it....BTW I will NEVER buy another one again....absolute JUNK!

if it's a tick, it's the lifters. GM 3.1,3.4 v-6's have zero lash lifters that will tick as they get older, and it's not an issue, just an annoyance. If it's a knock, and oil pressure seems fine, I would suspect piston slap, which is a problem you want to get taken care of ASAP, as it can cause Mr Piston to meet Mr Oil Pan in the worst kind of way.