i'm new to this forum stuff - so pls bear with me. I've got a 89 RS with a 5 liter and auto, 156k miles on it. Recently it started making some tapping noises outa the engine when it is cold - however only when it's in drive and accelerating. After it warms up a couple minutes it seems fine, and purrs like a kitten. Just sitting there idling, even cold, it sounds great. I took it to an engine shop and they listened and said it's likely sticky lifters. I've tried a couple of the juices in it, now running 1 qt of ATF along with my oil, and it's maybe getting a little better.

My question is - and i don't know much about engine internals - why do i just hear these sticky lifters upon acceleration and not at idle? Could my problem be something else that we're overlooking? thanks

try running some Lucas

yep, ran some Lucas first for a couple weeks. it really quieted it down, but only after the first couple minutes of operation. Still had, and has, the tick

could it be a valve tap?