To start off, My name is Mike. And I am new to this site. I got on here looking for an answer.

To paint the picture. I have a 96 Chevy c1500 5.7 Vortec 4l60e 2wd. To start off it blew the intake gasket. Typical for these trucks. When it did this it also cracked a head. So all the antifreeze dumped into the oil pan. Yay!!! Instead of messing with trying to tear the engine apart and cleaning it. I went with a reman 5.7 crate motor. Installed the engine. Working out the bugs so to say.

Now, I have a slight sputter around 60 mph on slight inclines when I barely put any access gas to it. I have replace alot of parts chasing this problem. Replaced with all new parts.

The list of new parts. Fuel pump, distributor, rotor button, cap, plugs, wires, coil, spider injection, fuel pressure regulator, knock sensor, cooling temp sensor. Like I said all brand new parts. No used parts.

Still have the problem. Not skipping. No codes or MIL. Set the distributor with a Snap-on scanner.

Ran compression test. 150 lbs across the board. New engine.

Fuel pressure test. Have 53 lbs upon start up. When I turn the key off it leaks down quick. takes less then 30 seconds to reach 10 lbs of fuel pressure. I know this is a fuel problem. But I can't seem to figure this one out. Any advice will be greatly appreciated. I have tried everything. So even if it is a stupid idea I will still give it a try to stop this. I'm thinking fuel or transmission.

 

Honestly standing fuel pressure, like what you're reading when the pressures drops real quick when the key is turned off, is really only going to impact your starting performance. If it cranks up and starts quick, then I really wouldn't worry about it.

Personally, now I'd want to test drive it myself before committing, I think it sounds like torque converter chatter. That's when the torque converter slips ever so slightly when you're in TQ lockup mode (aka 60MPH cruising on the freeway at operating temp) and you try and accelerate. Normally the shift control valve or the pressure control solenoid (I can't remember which) gets a signal from the PCM that you're accelerating and will turn off the Torque converter when you want lots of acceleration, sending it into unlocked mode. This will basically make the little shutter go away when it's in this TQ unlock mode.

So, TLDR, change trans fluid and filter and see what you got.

 

Thanks Nullhead. When I pulled the motor I dropped the trans and fluid. So I put new fluid, gasket, and filter in it then. I left that out.

 

Did you use super cheap trans fluid when you refilled? When I filled the trans on my project Firebird, I realized after driving it that the torque converter chatters something awful. Probably because I used the cheapest fluid I could find from advanced autoparts.

So does it seem like the truck sputters with engine power, or sputters like the trans coming out of TC lockup? Have you looked into the TPMS sensor being bad?