rough start on 1995 Volvo 960

just was given this car,it sat for 6 months prior. when you first start it up it runs rough, the rpms fluctuate. then when you put it in drive it hesitates for a few seconds, then clears up and runs great,even at stops,no problems. but if you shut it off even for a few minutes, the same thing happens. i changed plugs & fluids because it had been sitting for awhile.not sure why it does this at starts

Asked by for the 1995 Volvo 960
Can you check the diagnostic trouble codes and report back with what you find? Alos, check for vacuum leaks around the intake manifold gasket.
checked diagnostic codes, all came back clear. no check engine lights are on. also checked intake gasket using the brake cleaner method, but didnt notice any changes in idle. now it seems to be getting worse, hesitation is longer, then rpms increase for a few seconds before power kicks in. is there any other way to check for intake leak? thats the only thing i can think of too, because it runs great once it warms up