Hi, I am so stressed and have no idea what to do now. I have just purchased the car (2001 Buick Regal GS) and it ran great at date of purchase. The engine is still strong but will not for the life of me keep running. It acts like it needs fuel but we have not succeeded in diagnosing the fuel system. We assumed fuel filter and changed that, nothing changed. Then we thought that it could be the catalytic converter, needed changing but did not fix the problem. I just got through installing a new fuel pump and it is still doing the same thing. It will start strong but after several minutes it starts acting like it isn't getting fuel and will start to idle rough, then dip to very low rpm and surge back and eventually die. After it dies it acts like it has no fuel when trying to start. If you wait several hours or overnight you can try to start it and it will come to life like nothing happened but will then repeat the steps after running for several minutes.

We did the test on the fuel pressure regulator by taking the vacuum line off and seeing if fuel comes out but nothing past that. It has been sitting for two weeks (unfortunately money is hard to come by) and it is killing me not being able to drive it.

Please help as I really cannot afford to have a shop look at it.

Thanks, Mark

Has fuel pressure been measured?

Any codes?

When it won't start, disconnect the MAF and restart....

You need to properly diagnose it to avoid paying someone to diagnose it for you.

If you are concerned it is a fuel related issue, you should start by checking fuel pressure readings and behaviors. If the problem is what you think it is, it will be immediately apparent.

The first step is using a fuel pressure gauge.
Autozone Lone-A-Tool ($150 that you get back when the tool goes back):
OEM/Fuel pump diagnostic kit 27167- ReadReviews onOEM #27167
Harbor Freight ($20):
Fuel Injection Pump Tester

Many parts retailers can scan for codes at no charge, which may also be good to make sure there are no other surprises lurking.

Me thinks IAC valve sticking open. He says once started, it will run, then the ECU commands the idle to be turned down, it can't. So it stalls out. When the IAC is open in the morning, the engine will run fine because the ECU wants a higher RPM for warm up mode.

I would take the IAC off and give it a good cleaning, see if that helps...
https://www.gmforum.com/normal-maint...800-v6-307092/

I recall there being instructions in the box of a NEW IAC valve that I purchased years ago for adjustment to control proper operation of the pintle. I believe it screws in and out.