soloc4

I have an LS2 with the E40 ECM and a Speartech harness with LT headers, no cats, and no rear O2 sensors. After fixing all of the little issues with initial start, I have two DTC's P0171 and P0172 indicating a lean condition in closed loop. STFT is perfect, but LTFT is +28% - +30% at idle. Off idle the LTFT goes to zero as is expected. Speartech re-programmed the ECM to delete all emissions and cat related data, so why is the ECM still reading LTFT? Any help would be greatly appreciated.

Badas.sbird

LTFT will be active unless turned off in the calibration regardless of cat function or post cat oxygen sensor function. The LTFTs are not locked or tied to rear O2s in any way and as a matter of fact fueling calculations, during normal fuel strategy, do not use rear O2s at all. CAT overtemp routines can force the fuel richer but only as a safety. What you are describing is indicative of a vacuum leak.

soloc4

The only vacuum leak is the engineered controlled vacuum leak in the PCV system with catch can. This engine does not have EVAP, vacuum assist brakes (HydraBoost), or any other vacuum sourced accessories. Performed pressurized smoke testes, ether spray, there are no exhaust leaks, fuel pressure is stead 60lb. Not sure where to go from here. I want to get it dyno tuned, but I'm not going to pay $200/hr. to have someone diagnose it on the dyno. I agree, every indication leads to a vacuum leak, but I can't find it. I'm curious if anyone else has had the same issue with single O2 per bank, no cats?

Badas.sbird

Post a pic or two of your catch can routing.

soloc4

The catch can replaces the U-shaped rubber hose between the valley cover to the intake just behind the throttle body. The fresh air inlet runs from the inlet tube after the MAF to the passenger side valve cover. The catch can is sealed and will hold 40# of vacuum for several minutes on the bench. All of the connections have been tested by smoke and ether as stated above. Any thoughts?

Badas.sbird

Do you have HP Tuners or a copy of the Tune? Also just to completely put the catch can and PCV system to bed, block off the intake manifold vacuum supply and the fresh air supply after the MAF and log again. Look for changes in STFTs that would be close to opposite the values of your LTFTs..

soloc4

I do not have any tuning capabilities, software or knowledge, just a scan tool with live data capabilities. I did isolated the PCV from the system once with bad results, the crankcase pressure blew oil past the main seal, but I will try a different approach and cap the vacuum port and leave the crankcase vent open to atmosphere (cap the inlet port at the intake tube) and see what the trim numbers are. Interestingly, when I increase the fuel pressure, the LTFT comes down below the DTC trigger point. This is most likely the result of less dwell needed at the injectors, but is a crutch and I would rather correct the cause of the high trim at idle. Thank you for your time and experience Badas.sbird.

Badas.sbird

Yes you have to leave the valve cover and valley to vent.

soloc4

The frustration just keeps building. I removed the catch can from the equation and went from 1 code, P0171, to 3. I have P0507, P0300, and P0171. All indicate a massive vacuum leak, but I still can not locate the source. Looking at the live data shows that the O2 sensors reading different LTFT. RH is +11, while the LH is +18 - +20 at idle. I’m not sure what that is telling me. The left side is twice as bad as the right side, but both are out of spec.

Badas.sbird

And just to be sure, you did plug off the side of the manifold so there was no vacuum source to the PCV system correct? PO300 is a Random Misfire code. Does this have an aftermarket cam in it? Most cam cars have some kind of split from bank to bank but this is excessive. I wish you had a way of sending me the tune. I could look at it and at a glance tell you if there is something wrong in the calibration for your setup. It will need custom tuned regardless to be correct. The MAF sensor looks like an LS3/LS7 unit which most LS2s use a different MAF. The transfer function are very different between the 2. Also the location, orientation and pipe ID make a huge difference. If he left the MAF functional in the calibration, then it will 100% need a custom tune.

soloc4

Yes, the manifold vacuum source for the catch can was capped, and that is when all hell broke loose. I now suspect the nipple on the manifold has been compromised so I am going to remove the manifold and check it thoroughly and verify the integrity of all the gaskets. I've had an intermittent P0300 from the beginning, which I also suspect the cam is at fault (.238-.243, .613-.623, 112 LSA). The heads are PRC ported LS3's, so I have an LS3 manifold, therefore an LS3 MAF which I re-pinned from the LS2 connector. I would assume that SpearTech left the LS2 logic in the initial tune. The fuel system is bypass regulated with 50# injectors. the engine is a 408ci LS2, E40 24X ECM with a SpearTech base tune. I know that I will eventual figure this out, but it is frustrating. I appreciate all of the time that you have dedicated to my issues. I also wish I had data sharing capabilities, I could use the help in that department. I will get back with the results of the top end diagnoses.

MacRocZ

Did you solve this? I have same issue but no cam, no catch can. Just long tubes. Bank 1 is 25% at idle dips a bit on rev. Bank 2 looks correct.
Swapped HO2s to see if problem followed. Still Bank 1.

soloc4

Maybe, when I removed the intake I noticed that the left intake ports were not sealing properly at the bottom. I have the truck style steam vents and an LS3 manifold which prevented it from sealing. I clearances the bottom of the manifold to allow it to fully seat. Now for the, but…. I have not “driven” the car since I did this, just running it in the shop and I haven’t gotten any codes yet. The car is blown apart for paint, so it will be awhile before I can confirm the results.