Not sure if this is the right section. My girlfriend's 99 Tahoe 5.7L has been hestitating for a few months now and I cant seem to find the problem. It drives fine at low rpms but if i try floor it then it gets up to about 2500 rpm and then sputters and doesnt go any higher. Let off the gas and it's fine. Even when it's parked and reved it doesnt go past 2500 rpm. It seems like it's starving of fuel.

So far i did:

new spark plugs/wires
new cap and rotor
new fuel filter
seafoam

Nothing so far has helped. What should i try next? Fuel pump? Fuel pressure regulator?

 

5.7 LS1 Swap

 

Is it the 5.7L L31 Vortec?
Could be poppet injectors or a worn distributor gear...which is VERY common.

 

All strong possibilities. Of course check fuel and spark...I'm assuming comression is OK since it runs under normal conditions. Could be clogged cats also, clogged cats would keep the engine from revving up.

 

I was thinking cats too but wouldnt it throw codes?

 

Definately sounds like a clogged something.............

 

same deal happened with us on an 04 Sierra 3500HD... wouldn't rev past 2500rpm, logged it an it was tooooo lean! like no fuel was getting to it...

changed the fuel pump and it was sweet as ever... check that out.. (There were no DTCs for the fuel pump either)

 

I had clogged cats one time, and they wouldn't throw codes becouse they worked fine otherwise. Just somehow they got filled with crap, and wouldn't allow my motor to rev up past cruising speed.

 

I have personally witnessed identical symptoms separately from a bad fuel pump and from a dirty filter. You've got the filter handled.
When you go to drop that tank, be sure to keep small children out of earshot. Have Quick-Disconnect tools for the fuel lines ready.

 

Not always, I've seen cats clog that have caused a car to misfire under load and not rev past 4000 rpm that didn't throw any codes for the cats. (there was a blinking mil and random multiple misfire codes though)