Fuel pressure surge 5.3 swap

1992 k1500 blazer
5.3 swap from an 03 Avalanche
4l60e
3k stall
212/218 .600 cam
Walbro 255

I did a 5.3 swap in my blazer, from day one it has not ran correctly I can’t even drive it because of has such a bad misfire. I have spent the last couple of months troubleshooting and throwing money at it but so far I have no improvement.

It has a misfire but it isn’t throwing any codes, I did drive it once and within an 8th of a mile it threw a P0101 code, i had to clear the code for it to run again.
I have replaced the fuel pump , filter/reg, vac hoses, intake manifold gasket, MAF (with a used one) , I cleaned the Injectors and throttle body.

I use torque pro scan app, it shows no codes, no misfires, o2s are switching.

Here is a video of the fuel pressure https://youtu.be/S-UbH5Ogdq8


Here is another form thread with more detailed info. https://www.ls2.com/forums/showthrea...e-tech-support


Does anyone have any idea what the problem could be?:shots::whack:

When an aftermarket cam is installed the misfires are disabled.
That's why no misfires are showing.
Get them enabled so you can determine which cylinder is causing the issue.

The p101 code could be a wiring issue, bad maf or tuning.
Don't throw parts like that until this is done, it'll save money.

When an aftermarket cam is installed the misfires are disabled.
That's why no misfires are showing.
Get them enabled so you can determine which cylinder is causing the issue.

The p101 code could be a wiring issue, bad maf or tuning.
Don't throw parts like that until this is done, it'll save money.

Did you do the learn procedure on the crank.