henro

I put a 2003 5.3 and 4l60e in a 57 chev It runs but has a low idle and stumbles when you accelerate . motor set for 2 years but has no codes in computer has new fuel pump but has 43 lbs until I undo the vacumn at regulator then goes to 47. Has new fuel regulator new iac valve ,new throttle position sensor

davidws6

iTrader: (36)

Could be anything. Knock sensors to O2's . Your going to have to scan it with an O2 sensor to see what's going on. I think the fuel pressure should be 58psi

LS1MCSS

iTrader: (18)

Do whatever you have to do to get the fuel pressure up to 58lbs and then see how it runs.

allan808

iTrader: (3)

Needs to be 58lbs or itl run like ****.