1999 Buick Century Start rough idle and misfire

Would the ignition switch cause all of my mentioned problems?

If I change the ignition lock cylinder will I need to replace the key or will my current key work?

So the lock cylinder is by VIN? Then as long as the correct cyl is ordered it should not matter? I checked the resistance of the key and according to the number of resister ballasts (15) my key registered the last measures key, 15. If that is correct then when the dealer orders another cyl is it done by VIN or is it ordered willy nilly?

Sir I think you missed my question. We were talking about the lock cylinder. It's my understanding that my ignition lock cylinder is bad. The question is IF the cylinder is bad, would replacing the cylinder require a new key.

Let me give you the history if this problem. About a week now starting this car ha been a little difficult. It first would not crank when you turn the key. All of the dash lights would come on like normal, then go out. The first time you turn the key to start, nothing, no clicks no starter engagement. No. Indication of any other issues to include anything with the security indicator. Then a second or third turn and the car would start. This was an intermittent problem. Yesterday I went out to my car to start it early in the morning, and had the same issue, but then the car started on four occasions. Then later in the morning went out to start the car, I get a starter whine like it was starting the car, but obviously no ignition or spark. I am wondering though, if the ignition cylinder has two contacts that mate with the resister on the key because it looks like the lower contact in the key cylinder looks as if it may be stuck in the detent.

The reason I asked about the current key is will it work in the NEW lock cylinder or will the new cylinder have a new key and cutting template?
Also I've read that old fuel pumps have a pronounced whine as they age which would account for the sound I hear under my seat. Is replacing the lock cylinder as easy as I've seen on the Internet for this vehicle, or should intake it to the dealer to have this done? Thanks for your assistance with this maintenance issue.
Dennis

Ok so the switch is located near the multifunction switch?

I did thanks. Just looks like I'd have to order the part no matter where I go :)

Changed ignition switch, same results

All of the ignition system has been replaced. Wires, plugs, coils, ignition control module, I've checked all the fuses, and relays. All I get is a random misfire code. I have also replaced the upstream O2 sensor. The starting issue like it is now has only been happening a week. Yesterday awacs the first time the vehicle would not start. And turning the key in the start position did not even get a crank. Now it cranks or I should say turns but nothing else.

Initially this was a rough idle issue, then the idle was fixed, and found a misfire codes.

Will send car to buick thanks
Ill let you know what the issue is.