Need help

[1989Formula]

i am new to 4th gens and mine is starting to act up and i was wondering if anyone has advice / seen the issue before

basically after driving the car for over an hour at idle the rpms will surge and bounce from about 1000 -1800 rpm. At light throttle or cruising the rpms will swing 500rpm up /down of where it should be. However at WOT or even heavy throttle it will go away. this leads me to think its a vacuum issue since it occurs at low load, high vacuum conditions. I think its a IAC or TPS or even a VSS going bad. My air lines look ok , but might have a crack or something. It will also randomly go away ?

Thanks for any help ....i just pray its not a damn opti

car info : 1994 LT1 A4

[MP81]

Well, checking for vacuum leaks is pretty easy (well, the method - it's tedious as hell) - just spray them with carb cleaner (probably want to find suspicious areas) with the engine running. If RPMs increase when you do that, you've found one.

So it doesn't feel like it's misfiring at all?

[1989Formula]

Well, checking for vacuum leaks is pretty easy (well, the method - it's tedious as hell) - just spray them with carb cleaner (probably want to find suspicious areas) with the engine running. If RPMs increase when you do that, you've found one.

So it doesn't feel like it's misfiring at all?

no missfire and on service engine light. i put new air lines on it so i will see today if it helped anything

[MP81]

Yeah, let us know what happens...