Jeep LS swap idles 5 seconds dies can stay running with throttle

Hi i am on my second tune first being afm on 15 suburban which went good. Now i swapped 5.3 into my jeep out of 03 trailblazer. it is stock with different intake pipe no cam all parts of of good running truck. I made tune with out VATS and delete rear o2s because i have no cats. it starts and runs then dies 5 seconds in if it gets warm it will catch before it dies and revs up and then in 5 sec die again. i checked amazon harness had to repin MAF all seems good. Tried to make tunes to fix it still dies. Loaded factory VATS off tune same thing. Install my buddys ECM that is tuned for cammed engine that runs great. Tried copying what i saw different no change. Not sure what to do at yhis point any help would be great. :banghead:

If you can keep it running with throttle, you need to run it longer and data log it longer. Need to let the trims kick in and see what they do.

I have tried to record longer data but it wont come open loop but im not real sure why. ran engine for 10-15 i can force it but it wont go on its own.

First thing is you need a fuel pressure gauge on the vehicle. Second, it's a swap vehicle so there's no telling what it might be. You need to keep it running for as long as you can and data log it the entire time. Telling me you can run it for 10-15 seconds doesn't do much. Posting a 30 second log might.

It probably due to the placement of the MAF. But need to let it run long enough for the trims to kick in or turn them on manually with your scanner controls. Or just randomly add a bunch to the MAF table and see what that does.

so that is with stock intake tube and 48psi vacuum controlled fuel pressure. I did try to set this up as returnless fuel but have gone back wards till i can get this to idle. I had idle turned up to 2000rpm on scanner setting.

I do have 12v through surge out of fuel pump control relay and standalone run relay that powers ecm and engine control.

It's not going into closed loop most likely because you haven't turned off some codes and you probably don't have downstream O2s. You'll have to manually turn closed loop ON with your scanner controls.

Your pids list is terrible. But it looks dead lean. Try multiplying your MAF table by 1.2 from about 6000 Hz down and then blend it into the rest.

You can force it into closed loop with the scanner just to see if it is rich or leans.

I like to do a lot of swaps in speed density.. Where the MAF is placed.. where the filter is getting air.. can really screw up things.

Verify fuel pressure.

You might have to check that harness out. I've not heard one good thing about those harnesses.

The '03 Trailblazer pressure regulator should be 58 PSI ("55-62 psi" per the service manual), key on engine off, or running with the vacuum hose removed. Only the '04-down flex fuel L59 was return style/vacuum referenced at a different pressure (51 PSI).

Thanks for everyone?s help. Ended up being bad ecm or bad hp tuner load. I?m a little soured about that this was my second tune that cause me ecm and credits to unlock but may it was just a bad ecm.

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Originally Posted by Qcustom

Thanks for everyone?s help. Ended up being bad ecm or bad hp tuner load. I?m a little soured about that this was my second tune that cause me ecm and credits to unlock but may it was just a bad ecm.

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No.

Quote:

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Originally Posted by Qcustom

Thanks for everyone?s help. Ended up being bad ecm or bad hp tuner load. I?m a little soured about that this was my second tune that cause me ecm and credits to unlock but may it was just a bad ecm.

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this make no sense

He probably used a different ECM that had a stock tune and it ran on the stock tune.

I had already tried stock tune it ran the same. I made 10 tunes raising idle, increasing VE, adjusting injector flow rate for none return system, running fuel return and none fuel return, Copied tune in other ECM that my friend had had tuned and it still actted the same engine would idle up and back down and may die or do that a couple times and die. it wouldn't run on stock tune, swapped ecm ran 90% better, adjusted VE a little way better at idle.