5.3 Swap Wont Idle

I am new to HPtuners and I'm having some trouble with a stock 5.3 swap I recently did. The donor truck a 2000 GMC ran fine. I pulled the motor and swapped it into a 93 Chevy truck I deleted the EGR AIR Pump And EVAP system. It fires right up and almost immediately dies. The VATS has been disabled. If I keep it running and slowly let of the accelerator it will idle but if I bring the RPM's up and let off it dies. I replaced the IAC it fired right up and idled high but then settled down to a normal idle. Turned it off and started it back up with the same start and die. Is there something in the tuning that I missed or do you think its a mechanical problem. Thanks for you help.

what fuel pump are you using? Have you checked fuel pressure at the rail?

Sounds like a vacuum leak. Had the same problem with my FAST intake. It wasnt sitting all the way down on the heads and it created a very small vacuum leak. It would fire right up and die. I could keep it running with the pedal and and slowly pedal it to idle and once it idled it was ok for about 30 seconds then the IAC motor would send it into a continuous surge that would eventually lead to stalling.

Also, where did you get the stock tune from? did you pull it off the PCM that came with the engine?

Its a Walboro 255 Fuel pressure is 55-60psi at the rail. I pulled the stock tune off computer that came with it. Once I get it to idle it will idle all day long no problem. Does the Evap purge solenoid or the EGR open at startup?

Bottom line is that the truck should run if you have the stock tune in the pcm that came with the truck. I assuming by the name of the file that you have modified the tune beyond just turning off VATS. To eliminate something that you did to the tune to cause the issue, I would reload the stock tune and then just turn off VATS. Don't mess with anything else. The truck should run. It will throw some codes for emission related stuff, but those don't keep it from running.

I assuming here that your wiring harness is all correct and that you have an intake tube, MAF, and air filter in place, and that you have at least the front O2 sensors installed.

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Originally Posted by demarest652

Its a Walboro 255 Fuel pressure is 55-60psi at the rail. I pulled the stock tune off computer that came with it. Once I get it to idle it will idle all day long no problem. Does the Evap purge solenoid or the EGR open at startup?

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You said it will idle all day long after you pedal it to an idle but in your scan as soon as you hit the pedal it will die after a rev. Which sounds like an airflow problem.

Do what jcrumpley said which is go back to the original file you pulled from the pcm and just turn off the VATS. If it still does not start on its own I would begin to look around that intake and make sure you have all the vacuum ports plugged. Even the brake booster... could have a bad diaphragm in the brake booster. . and since you took off the EGR make sure whatever you used to block it off that it is sealed as well. If you had the intake off make sure you dont have a wire pinched in between the gaskets. But like he said... if you havent changed anything mechanically on the engine it should run with a stock tune.