idle stumble and afr surging.

[Criegel]

having issue with a 5.3 swap im doing. stock 2002 5.3 with a Th400 in a 84 K10 with cold air intake and full length headers.Fuel pump is an AEM 400lph inline. I have about 12" of pipe after the o2 sensor.The tune in the p01 now is the same tune i ran in my c10 swap a few years ago and had zero issues so i am confident in it.The truck runs and idles good until about 152 degrees engine coolant temp. The Afr leans out and the truck will stumble almost cutting off then go rich and and level
out then back all over again.the pump wines every time the Afr goes lean we have swapped intake manifold,injectors,coils,map,fuel rails, fuel reg,Iac,new plugs and wires and did Tps relearn.i have tried open lope and also Maf failed in open loop. The plugs are Ngk Tr5 and black on all 8. the only thing i have not done yet is a compression check and i have not pulled the valve covers to inspect for collapsed lifter or broken spring.it revs nice and sounds healthy so i cant see it being mechanical. i have also tried adding 5-15% to the Ve and tried pulling 5-15% from the Ve with out any changes. i put it back to stock tune for now. i fell this set up should run fine on stock tune till we get this issue resolved and do more tuning. i cant tune it the way it is running now. Waiting on new fuel pump to come to rule this one out. if this was a 4.8 and not a 5.3 would this be an issue?19-10-19 14-54-36.hpl19-10-19 15-19-27.hpl

[5FDP]

You'll want a much longer exhaust if you want to use the narrow band o2 sensors or a wideband sensor. That is too short of piping and will skew the readings.

[RobG8LS3480]

Was it the fuel pump ? or maybe fuel table ?

[Donny O.]

we just had a similar issue when we swapped injectors. they were supposed to be the same as what we were told were in the car when we purchased it but then did exactly as you just described....fine til got warmed up a bit then surged and afr was sweeping. I searched and found the injector data for what we put in there(again was supposed to be the same "deka 80s" that came out) but the injector data was completely different than what was in my tune. so put the new data in and it idles fine now. not sure if that helps but thats what worked for me.