there's a few problems that i'm having and I think they're all related to each other, i just cant figure out what it is and im wondering whats everyones input on it.

rough start when cold. idling/driving rpm is jumpy/drag when accelerating, totally random. this is not like a big 500rpm + jump its somewhere like 100-200, enough to feel that something is wrong. it feels like the car is rocking back and forth for a second. hissing sound after the car has been shut off near the brake booster area in the engine bay.

I clean distributor cap, rotor, new spark plugs. cleaned iavc.

first problem I thought of is the ignition coil inside the distributor, i havent tested out its readings yet, second is vacuum hose leak. third probably fuel filter? anyone know what these symptoms lead to?

 

The hissing noise is normal and its coming from the intake, its simply the air being sucked in and passing through the throttle body butterfly on the last few strokes of the motor.

If you know someone with the same car/engine then borrow their distributor and see if the symptoms are still there, if theyre not then you'll know its related to the distributor. There is no point cleaning the distributor cap and rotor, cleaning does nothing, theyre serviceable parts and cheap so replace them and eliminate them as the problem from the outset.

I'd order a new distributor coil as the symptoms sound like its at fault, however it could also be your O2 sensor. Whats your gas/mileage like?

 

The hissing sound lasts about 30 seconds after the motor has been shut off. I compared to a friends LS and his doesnt have it so I wonder, hard to find exactly where that hiss is. I ordered a new coil a few days ago for really cheap so i'll try that when it gets here. as for my o2 sensor, im only running 1 o2 with jdm itr ecu, i'll try switching it with a spare. i'm getting between 22-26 mpg; i dont know if thats really low or average what do you think?

 

Hissing problem?...sounds like you have a cat stuck in your engine.

-All jokes aside, come back when you try our the new coil and if the problem isn't solved, go from there...

-The hissing noise could be the a/c condenser blowing off air when you shut off the car, or, it could be a vaccum leak. Have you tried popping the hood and trying to locate where the sound is coming from? Try listen and feel around for air currents.