no gas/power on ignition for 20 seconds?

1998 Chevy Blazer 4WD
85k miles

I've had this problem for a while. Whenever I first startup the vehicle, it sort of sputters like it's not getting enough gas. I can floor the pedal and it just wont go more than 5mph or so. It lasts about 20 seconds then there's normal power, and no problems thereafter. Pumping the gas has no effect. It happens anytime there's a cold-start, and sometimes on warm-starts too. Any ideas?

If yours has the vortec plenum intake with the injection hidden inside the plenum then it may be a fuel leak inside the intake. If it is then you may see some black smoke out the exhaust pipe when it is acting up.

Here's 2 tests if you had the time and are cheap and easy.

Turn key on and hear pump run once every hour until you want to drive it. If it is WAY worse then it is leaking.

Let it set for a number of days and then go ahead and cold start it again, if it is way better then it is leaking.

If you have a pressure gage, the test port is on the back of manifold to perform a leak-down test.

can you elaborate on this leak-down test?

if it is a leak, wouldn't that effect the overall performance? once I get it going, I can drive for hours with no problems at all.

If this is what's happening then the leak is a very tiny leak and the amount of leakage is very insignificant when the engine is running, especially at higher speeds and for longer than 20 seconds.

The significance shows up as the fuel continues to leak for as long as it takes the system pressure to drop to zero and if the leak is in the right spot will puddle up in the intake accounting for a nice rich mixture when starting.

After the gas vapor is used up in the intake it then becomes pretty un-noticaeble again.

The two tests I gave you were at opposite ends of making it worse (turning key on and repressuring the system repeatedly) AND making it a lot better (allowing it to set for a number of days to allow the amount of leak to simply evaporate thus not showing up at all)

There are threads here on the pressure test, but requires a pressure gage installation onto the pressure port, turning on key reading pressure and then letting it set for a length of time. If there's a leak in between the pump and the other end the pressure will not hold, it will fall off (leaking into plenum)

The two tests I made up along with the pressure test will tell a lot without ever taking anything apart. Just takes some time.