missing at idle

Noticed a couple of days ago that my buick has developed a miss at idle both in park and drive. Plugs and wires are about 5 months old. I havent changed the coil packs yet. Theres no check engine light. It doesnt hesitate under any throttle position. Do you think its my coils? IAC etc.

If it was a persistent miss, you would get a CEL. It would also tell you which cylinder was missing. If you scan the engine, you can look at the misfire history for all 6 cylinders. The PCM keeps track of the misfires with an actual counter. Each coil fires 2 cylinders pairs. Those pairs are called companion cylinders. On our engines, they are 1-4, 2-5, and 3-6. If the misfire history reveals misfires on a pair of companion cylinders, I'd suspect that particular coil, but not otherwise. Do some diagnostic testing before you replace parts unnecessarily. Just my .02

That sounds more like dirty fuel injectors to me. I was amazed at the difference in idle quality after I had mine bench cleaned. It would miss and sometimes 'spit' a little bit. Like there was raw gas dripping into a cylinder that wouldn't fire right, and sometimes it would pop in the exhaust pipe. After clean injectors - smooth as silk.

Try disconnecting one injector at a time and see if one of them makes the idle smooth out.

Yup no check engine light. Its definitely an erratic idle. WOuld a vacuum leay2k cause this? If so, what would i use to detect it. Cleaningthe injectors is a good idea

And yes the tach needle does go up and down, id say no more than two tick marks. Whats the worst that can happen?

Just put a vacuum gauge on it. I have a vacuum/boost gauge on mine. It pulls a steady 20" of vacuum at idle, in Park, fully warmed up. Anything less than that, you have a vacuum leak.

Wait a minute. My aeroforce gauge reads boost. But at idle i think it reads vacuum in the negative. Itll will jump from -19 to -17.9