98 BUICK REGAL MISSFIRE FROM #4

My 05 rendezvous was doing the same thing. If you have an evap solenoid on your model, it may need replacing. Fixed mine right up.

I suggest you use an OBDI code reader.

I would change your plugs and wires with original a/c delco factory wires and plugs.My buick did the same and got corrected with factory wires and plugs.I tried most of the after market and they didn't do the job.

Where all those parts, so bad,they had to be replaced? You tested them to determine that,and only then,you replaced them? Correct? Now you need help?

misfire only comes from the coil packs.. replace them

The error that I'm showing for error code P1133 is 
P1133 Heated Oxygen Sensor (HO2S) insufficient switching bank 1 sensor 1(Rear Bank).  I would suggest having both of your Oxygen Sensors replaced if you haven't already had that done.  Hope this helps.  Thanks for an honest rating and for using FixYa.

Need to check for fault codes. Possibly a faulty sensor causing the fuel system to run rich or lean.

Yes it can be a clogged or bad injector or low compression in cylinder #2. Remove the plugs and run a compression test first. If compression is good I'd say it was a bad injector.

check one of your coolant sensor's

Possible solution to stalling '99 Buick. My '99 Buick Century would die for no apparant reason with no error codes. After 4 days at a Buick dealership and many frustrated mechanics, the problem was corrosion from under the battery location. The wiring harness had small amounts of corrosion internally. Check the wiring under the battery for any corrosion. This has been the problem on more than 1 vehicle that we are aware of. No service bulletin has been issued by Buick.