99 Silverado 5.7 Vortec. Hesitation

kitttransam · October 10, 2007

This is a truck that belongs to my friend and i've been scratching my head. It's a 99 silverado c1500 with the 5.7 vortec engine. It has a bad hesitation. I drove it and the hesitation starts at around 4,000 rpm's and would not go past 4,500 rpm's (WOT). Has a major power loss. I replaced the fuel filter and air filter. I checked the fuel pressure it's at 61psi with engine off 50psi engine running. I checked the cap and rotor and found some corrosion. Before replacing those parts i removed the corrosion with some sandpaper. I started to check the spark plugs and noticed they were bosch platinum +2's (heard their junk) And one plug wire had a bad boot and the wire sliped out of the terminal. I replaced the boot and put terminal back on. After doing those things there was a little improvment. The engine would go past 5,000 but it still hesitates around the 4,000 range and it took alot to get to 5,000. I am wondering if doing a tune up would get rid of the hesitation or is it a combination of it needing a tune up and possibly the fuel pump might be going bad? I am open to all opinions.

ChevyTech007 · October 10, 2007

You need to have a back pressure test done to the exhaust. Sounds like stopped up catalytic converters.

kitttransam · October 10, 2007

I also forgot to mention it is hard to start after setting for a while. Starts right up if shut off and started again. And it does have an exhaust leak on the passenger side. Could have been caused by cats startin to plug. And it has a slight backfire.

GMTRUCKTECH · October 11, 2007

You need to have a back pressure test done to the exhaust. Sounds like stopped up catalytic converters.

also you may have enough fuel pressure but not enough fuel volume. The way I check fuel volume is if your fuel pressure tester has a bleed off hose your good to go. Hook up your fuel pressure tester as normal get your vec at operating temp. Place the bleed off hose in a container to catch the fuel and with the engine running hit the bleed off button on the fuel pressure tester. If the vec stalls your fuel pump has weak volume if not check your exhaust back pressure. A good fuel pump will not let the vec stall.