Buick regal 2001, engine rpm = 2500 max - 2001 Buick Regal

How long since a tune-up? Any applicable trouble codes? To check codes, yourself, at the least, you need an obd2 code reader. Some of the national brand autostores will check codes for free, if there are any.

I'd look at cleaning the throttle body first.
Here's a how-to
Throttle Body Cleaning GM 3 8L Series 2

That's normal; this protects your engine from over-rev damage.

Replace the crankshaft sensor and the cam sensor. I had the same problem. Good luck.

It sounds like your idle control valve is sticking. The video shows you where they are located on a 97 Buick but it is the same engine.
This video shows you how to replace them.

Hello! The defective ignition coil more than likely contaminated the downstream O2 sensor...If there isn't a trouble code and engine performs in a normal fashion, there's no reason to change the upstream sensor...

Guru........Saailer



I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Fuel Pressure Regulator

Suggestion only! If you had no shake before the tranny work,then retracing the steps backwards is a good way to find the new problem.
Go back to the tranny shop and complain #2 go to another tranny shop and get a professional to look at their work.

The ignition switch on that model is rated @ 50amps. When I was driving my 2001 Regal LS (at 120,000 miles) and used the turn signal, the engine would die, when I switched the turn signal off, the engine ran. So I replaced the ignition switch, and all is well.

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Sounds like a plugged catylic convertor. You might check with a GM dealer to make sure if it falls in the Special Policy coverage to get it replaced under warrenty, it has to have less than 120,000 miles on it though.