I have a 1985 500 SEC, has a little bit of a rough idle, but only when a/c is off, when a/c is on idle smooths out. I posted a question about this, and answers were cleaning the throttle body. Cleaned throttle body, still no change. I saw a thread about the Trans Modulator, my car does go into gear from park a little hard and jerky, not smooth, could the trans modulator be the answer for both the rough idle and the jerky gear change? All cylinders were checked for compression loss, all were perfect, which illiminates bad valves. The rough idle smooths out at around 1200-1300 rpms and then runs like a gem! It seems to be more of an air / vacuum problem, as with the a/c on, you cant even tell the car is running!! I would appreciate any help with this problem. Thanks!