5.2 to a 5.9 gas motor swap is done but I'm needing help
 

Ok so here's the deal. I swapped out my 5.2 to a 5.9 it was a full swap motor and transmission. It was a really good swap everything went great. But the ecu.im needing help. I bought a hole parts truck for this swap. So when I start the truck with the 5.9 ecu in it. It runs for about one second then dies but if I hookup the 5.2 ecu it runs and start but is under power and doesn't shift right. So then I hook up the 5.9 ecu start the truck and before it dies we spray it with gas it will stay running. So for some reason the 5.9 ecu is turning off the fuel does anyone know what's going on I'm lost on it thank u so much for UR help. Btw the truck is a 1998

keep your stock 5.2 ecm, get a aem uego wideband, and get a tuner/tune from hemifever. thats all you need to do.

been there done that. still running my 5.2 ecm, and tuned over the factory tune.

Little bit off topic from OP, but doesn't keeping a 5.2 ecm on a 5.9 engine swap not allow full power to the 5.9 engine?

I dont know 100% but have read that multiple times

Read my post above... Swap complete for 2 years now and I still have my 5.2 ecm.

All that needs to be done is buy a wideband, and get a tune from hemifever for a 5.9, and dial it in with the wideband.

In my case, I got a custom tune, because I have way more than just a swapped motor.

motorboat,
What Redneck is talking about is that he keeps the 5.2 PCM but then gets a SCT tuner and flashes the PCM with new software that would be the same as having a 5.9 PCM. The good thing about this is that you can overwrite the death flash if you have it plus Hemifever can write a better program than what comes from the factory.