Sammynoir

Hi all , new to this forum. My dad has a stock LS3 4runner meant for offroad-racing. After having blown an LS1 and LS2. I am helping him build something reliable. At the moment I have gotten the swap running and mapped but I am facing issues with the engine going lean at high rpms. I am looking for a tuner who can help me diagnose as well as map my car correctly. The current tuner out of Kuwait has alot of projects and is slow to respond. In my diagnosis I have observed. It is an LS3 swapped to the exhaust system of an LS2. I am using the MAF sensor from the LS2. 58 psi is the ls3 requirement for fuel pressure at rail.

1. Fuel pressure at switch on goes to about 60 psi, immediately drops to 40 psi and I get some fuel in the return line. Slowly bleeds out till below 10 with no fuel coming in the return line from 40-10 psi. I am running a pre filter to (new) walbro gsl392 to Fuel Lab FPR (just put in a new diaphragm) to fuel rail. Returnless style , the fuel pump does not have a check valve. I read on LStech forums its normal for this pump to drop from 60-40 at switch on. The car cranks for a long time when the pressure has dropped for a bit. If I crank it closer to switch on it starts up quicker than after a delay, directly co-relating to the fuel pressure drop.

2. When making runs my tuner pointed out that I have some mechanical issue in fuel. I get 13v at all times at pump and in my last runs using an electronic fuel pressure gauge my mechanic claims(will recheck with my own eyes) that fuel pressure is holding near 58-60psi all the way to the top. My WOT AFR reading until 4000ish rpm maintains the sweet spot of between 12.5-13 but after 4000 rpm starts going up all the way till 13.8 near redline. I am using innovate LC-2 wideband to track WOT AFR and have it plugged into HP Tuners.

3. I just put new o2 Sensors and at idle my o2 readings seem weird with Bank 1 showing 33mv and Bank 2 703 mv on HP Tuner. It also gives me P0103 - Mass or Volume Air Flow A Circuit High. When I disconnect the connector on my MAF sensor the engine DOES NOT shut off (maybe due to tuned map) o2 readings change and engine noise slightly changes.

4. So now I am considering throwing on a new Aeromotive FPR to rule out the fuel lab FPR unit being bad ( however I have been in contact with techs at Fuel lab who claim their spring never goes bad and a new diaphragm is good enough maintenance. When I plug the return line to the tank shut the pressure holds around 40 psi but still has some very small creep downwards.

a ) Do I have a fuel injector that is stuck open at 70-80 percent ?? (read on LStech forums that one O2 showing low and one o2 showing high is a sign of injector stuck) as to a possible cause of fuel pressure leak as well as lean. The car has no misfire but my tuner did say that he noticed a knock when viewing in the map.

b) am also now wondering if I have a Vaccum leak and excess air is entering into the system at high load above 4000 rpm or a malfunctioning MAF sensor is letting in too much air ??

c) Also am wondering if fuel pressure is holding to the top does that mean that the required volume of fuel is also getting there ? There is a minor difference of about 2 psi between fuel pressure at FPR and at rail. The lines are not choked from anywhere. The distance from tank to engine is roughly 2.5-3metres . Tank sits behind the drivers cabin.

d) Thinking of taking car to dyno to recheck fuel pressure is holding till top and cross verify my AFR reading using the dynos AFR sniffer. Although I just calibrated the LC2 wideband sensor and checked the bung and exhaust for leaks. No leaks on a basic check.

Non related but my IAT is also showing red as in high intake air temp. Any help or any checklist of things to do would be much appreciated and if I can connect with someone who is able to read my maps or tune the engine further after reading my maps if anything there needs to be changed.

I attach the map , latest log at idle , latest log run , WOT AFR vid, videos for fuel pressure dropping at switch on + videos and o2 reading pics to help in analyzing what is going on and which areas should I target. Also a picture of the truck

RB04Av

I can't be bothered looking at all that CRAP. Meaningless gibberish and monkey-spank.

99.999% of the time when a motor larger or otherwise more powerful (fuel thirsty) than whatever came in the chassis is installed, if it goes lean at high RPM, it's because the fuel system can't deliver enough fuel to keep up with the engine's demand. The other .001% of the time, it's because the fuel system can't deliver enough fuel to keep up with the engine's demand.

Ummmmm....

You do the math.