Folks, I've been chasing a starting problem for like 2 years. I put less than 1000 miles on the car this past year.

The problem is, the car will not start unless I pump the gas pedal while turning the key. Otherwise it just keeps rolling but won't fire. I know pumping the pedal doesn't feed gas, but rather opens the TB butterfly to allow air. So why might this be happening?

There is a long list of things I've done to fix this

Please state what car you have and what you have done so far.

Ah, sorry. 02 Buick regal GS.

So I've done a lot. When the issue started, I suspected the MAF. Ordered a new MAF for an 02, found out I had the TB from a 97. Then I found out I have a gen 3 blower. Bought an L67 TB, installed w/ new gasket. New MAF. Same thing.

I done the rest as well: new fuel lines and filter, vac lines, IAC, I THINK I've done the TPS, maybe not. New spark plugs and new FPR, new fuel pressure sensor.

All I can think to do is the fuel pump which I've been in denial over. Gonna rent a fuel pressure gauge to see what it'* sitting at. I think my buddy said it was like 25 when it should be around 42

25 psi and it accelerates under a load ok?

When you accel, do you "feel" the boost?

Not sure if your '02 had the special fuel pump circuit(used a ceramic resistor)......

More often than not, when you have to hold that throttle plate open, you are not getting enough air on start up....either the throttle body bore/plate is dirty or not adjusted correctly, or you have a problem with the IAC valve, circuit, or passageway....

Last time fuel filter replaced?

Scanned for codes?

What happens, if instead of stepping on the gas pedal, you turn the key to "on"(Don't crank), then shut off for 5 seconds......turn to "on", shut off for 5 seconds...repeat one more time......now try to start the car normally without touching the gas pedal...

And you definitely have to get a fuel pressure gage on this....observe if the fuel pressure increases when you try the procedure I suggested....

Yes, I absolutely feel the boost. The TB was thoroughly cleaned when it was installed, about 2 years ago and as I said, I've put less than 1000 miles on it the past 18 months.

As for the IAC valve, circuit, or passageway, can you elaborate?

Fuel filter was replaced when the new lines were done, close to 3 years/10000 miles

I'll scan again for codes, last codes i saw were from an open ABS circuit from when I did the wheel bearings, and a P0446 which hasn't come back since I swapped the fuel pressure sensor.

I've tried the key on/off thing, no dice.

The IAC provides "by-pass" air around the throttle plate, to control idle speed without using the throttle plate......

You changed the throttle body....did you transfer the old IAC valve to it, or did you use the one that came with it?

If the IAC valve is bad, or if it'* pintle is dirty and the passageway in the throttle body is gummed up, or if there is a harness problem(bad female connectors too wide, broken wire in the harness), this can cause the IAC to malfunction......so when you slightly step on the gas pedal you are allowing more air in, which the IAC should be doing for you.....

And like you say, the other possibility is a TPS.......

I'll thoroughly recheck the IAC. I genuinely don't remember if I got a new IAC or used the old, which would have been an IAC from a 97 TB, idk if it'* relevant.

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Slightly off topic, has anyone had any experience with vapor lock?

Not on anything like your car. It'* pretty much unheard of these days.

If you have to gently hold the throttle open a little bit to get it to start, then its IAC valve related.