sniper7

Hopefully you guys can help me. The shop I took it to couldn't come up with anything for me.

1997 Silverado Z71 4x4 5.7L automatic extended cab.
138000 miles

while driving I noticed it felt like the truck was slightly surging and I was lacking power. Was doing 65 mph.
The surge was almost like it was losing power, but had just enough to hold speed or slightly bleed it off.

Eventually I hit traffic and had to slow. When I went to accelerate, there pretty much was nothing. I eventually got it up to speed and starting looking for an exit. Giving it more gas compounded the problem and it was better to just try and barely give it enough gas to accelerate to get any speed.

I did put the truck into neutral and revved the motor once. It only went to about 2500 rpm and wasn't as good as normal. some muffler popping noise.

After putting it back in gear I had the same issues with lack of power so I took the next exit.

After stopping, the truck seemed to idle fine. I hit the gas and got almost no acceleration. When I let off the gas the truck felt like it connected a bit more power and I got some speed. I limped it into a parking lot. When I tried to hit the gas hard (say for a downshift to accelerate) I got nothing, just sputtering, and it almost sounded like a popping coming from behind me. popping in the muffler I think.

I got it stopped in the parking lot and it was idling fine. I popped the hood, looked for leaks or anything like that, look under the truck and didn't see anything out of the ordinary. from inside the engine compartment I tried to rev the motor, it sounded like it sucked some air and died.

Tried to start it after about 5 minutes and got nothing.

I got it home the next day, took the bed off, replaced the fuel pump and filter. started it, shut it off, started it, shut it off...about 5 times. let it warm up and I was going to drive it. just backed out of the driveway and it started running rough again. left it sit overnight. The next day it started up and drove fine....
after the truck warmed up, say 20 minutes, the truck experience the same problems as before and struggled to run and would run really rough and muffler pop etc.

I took it to a shop, same thing occurred while the mechanic rode with a computer hooked up and didn't see anything out of the ordinary. sometimes he mentioned it was running a little lean or a little rich. They drilled into the exhaust and tested the pressure, no problems there. they said the cats were probably good...I thought they might be plugged.
they tested fuel pressure and it was right around 55-60 at idle and 60-65 with power.
he checked spark plugs wire voltage and that seemed to be fine. they couldn't come up with anything so they told me to just give it a tune up and see what happened.

I replaced spark plugs and wires the other day. started up and ran fine afterwards. left it site for a day.

today I went out, it started up fine, drove fine, stopped to get something at a gas station. went to start the truck and nothing....
same no start issues I had before. It would turn, but not fire. then while it was turning, it was almost like it got stuck and would really labor to turn the engine over. I know the battery is somewhat weak, but I even hooked it up with jumper cables to another batter and it was the same issue. it would turn, then labor really hard and almost stop (like a dead battery).

I am just very frustrated with it. any help is appreciated

shamrock246

I had a crank sensor fail and do what your describing in you last paragraph it tore up a starter and flexplate