ls swap in square body running poor

[cr92]

hey all,

recently swapped a 4.8 vortec/4l60e in my 87 chev r10. having some idle issues and its not running very good at all in drive. i followed the wiring harness setup through lt1swap.. but it seems like its running hot on bank 1 with MAF sensor plugged in... it was shooting sparks and i could see inside the cat was blood red ( exhaust only reaches past the catalytic converters)

when i unplug the MAF it idles good but you can see a bit of black smoke coming from it so it must be running rich.

donor truck ran good before swap, drove it 70 miles no problems. only thing i can say is that the map sensor got broken from the engine hoist plate we had mad so i replaced that with a map sensor someone gave me from a 5.3, the part numbers are different but on rock auto they cross reference so that should be fine..

tried swapping MAF sensors with a good running ls swap, different map sensor, different computer, checked spark plug wires for spark, 02 voltages with MAF plugged in were around 450mv on bank 1 at idle and were pretty much showing 0mv on bank 2, and then with MAF plugged in was showing 450mv on bank 1 and around 150mv on bank 2.. seems a bit low to me..

Fuel pressure was showing around 43psi with key ahead then dropping to 15psi after a few seconds, 43 psi steady while running. we checked my friends 5.3 swapped square body and his is showing 50psi key ahead and running. and a 2012 5.3 which would show 67psi key ahead then 45psi running and it runs perfect. those numbers seem low but both other trucks except for mine run and drive great? i tried the fuel pressure tester on my pontiac g5 and that shows 58psi constant key off or car started so i know the gauge is working?

[jweb]

It sounds like you may have multiple issues. I have 58 psi constantly on my ls1 swap. I'm using a corvette style filter/regulator, what do you have for a regulator?

The first filter/regulator I installed was no good, so I would try that. I'm no expert and still have some problems myself.

[Zoomad75]

You are kind of all over the place for info. Hot running on one bank? Runs better with the MAF unplugged, but rich? Map sensor broke, but replaced with another number?

Have you done anything to get actual data from the engine control system? Here's why I ask. You state it ran better with the MAF unplugged? The concern I have with that is the MAF is the reading for the entire engine, not just one bank over the other. Same goes for the MAP. Fuel pressure is the same, it's feeding the fuel rail all the same so unless you got a plugged rail I doubt it's a fuel delivery issue. Although your fuel pressure is low as it should be 55-60 psi running.

So if the MAF, MAP and fuel pressure are common to the entire engine you need to start looking at what is specific to the side or bank in question. So you got to look at the o2 sensor reading? Is it switching normally? Trending rich or lean? What's the fuel trim reading bank to bank? Do they differ? The wiring to the coils are separate bank to bank so are the coils firing correctly? Unburned fuel in a cat will light it off red hot too. Did you look for any misfire readings per cylinder?

What it boils down to if you aren't reading data from the ECM, it's similar to trying to navigate without a road map. Sure you might eventually find where you need to go but it's going to take forever and possibly cost a fortune swapping parts out. This is where the EFI can really help you figure out the problems. Knowing what sensors should be reading from the service manual and then seeing what the actual data is will point you down the path to address the problem. Think logically. You'll find the problem.

[68GMCCustom]

are there any codes?

[truckdude239]

If a cat is glowing then you are dumping raw unburt fuel into that side so misfires or dead cylinders

[cr92]

hey thanks for the reply.

trucks showing no codes except for the 2 emissions codes

as for the regulator I'm not sure. its a return-style fuel system so i was under the impression the regulator was on the fuel rail? it has the ep381 pump, stock fuel filter from the 87 4.3 V6 TBI is still on there.

the o2 sensors move around a little bit but mostly stay around 650mv on the side i "thought" was rich, and it was down around 160mv on the other side(bank2)

as for the fuel trim, I'm not sure what i should be looking for?

The MAF was showing around 70 #/m at idle(unsure what the measurement is)
and IAT was 40F so i know both of them are working, and i tried swapping the MAF and that didn't help.

the MAP sensor has a different part number on it but as far as i can tell on rock auto it interchanges with the stock one, so map shouldn't be a problem.

idle is around the 600rpm mark

the truck just seems to have a slight misfire somewhere with the MAF plugged in, seems to smoothen right out when i unplug it..

i drove it up the street it seemed to be running good until i got about a km away then it started running like ****, i stopped turned it off and it started right back up and idled fine... i would really like to see a higher fuel pressure reading from this truck, and try atleast 1 new o2 sensor to eliminate that.