Vortec 7.4, 0411 PCM, Standalone Harness...got a ?

[Oxyacetylene]

I just completed the 0411 PCM swap on my 97 model Vortec 7.4. This engine is in an 89 suburban using a standalone wiring harness, from Painless. I have loaded the calibrations for the 2001 Express Van. The OS running is 12212156. I do not have a VSS hooked up since the 89 suburban didn't have one. I am using a 4spd (SM465) transmission.

Here's the issue: cranks and idles fine, but if I try to rev it up when it gets to a little under 2000 RPM it tries to die. I am wondering if the abuse management parameters are making it do this? If I ground pins 32&34 on the blue connector as if I were going to do a crank relearn, then it doesn't do this at all. Maybe the abuse management is kicking in because I don't have VSS hooked up, manual trans, and no park neutral or clutch signals?

[hog]

You are correct. You need to raise your Abuse Mode Enable rpms, or give the PCM a VSS input, or ZERO out your Abuse Mode Disable Speed.

peace
Hog

[chevy052500hd]

also raise your p/n rev limiter otherwise it won't rev passed that because the pcm thinks in it in park. I have attached a stock camaro tune with no autotrans, try doing a transmission segment swap to eliminate any autotrans related issues.

[Oxyacetylene]

Thank you both. I modified the abuse mode parameters and that did the trick. Now I am wondering if I have a sluggish O2 sensor making the LTFT on one bank lean out more than the other by about 6-7%, or is that OK? The reason I suspect the sensor is because I have one old one and one relatively new one. The engine seems to idle pretty good, but throttle response seems poor until it gets up to operating temp. I am VERY new to EFI tuning :)

Would someone like to take a look at the tune I am using and see if anything stands out with the engine parameters? I received the file from another helpful user to have a starting point. The tune was originally for a 5.7 Express Van and I don't know how much it has been changed to account for the 7.4. I modified the injector flow rate since I also installed a set of LS6 injectors, rated to flow around 32lbs at 4 bar, but I set it to 31lbs due to some figures I found online where someone had a set flow tested.

[chevy052500hd]

Do you have access to a wide band o2 sensor, I am thinking that some ve tuning may be in order since the 7.4 is going to have different fuel requirements than the 5.7. I also compared a vortec box cal for the 7.4l, to the tune your running the maf sensor calibrations are a little different, are all the sensors orginal to this engine? Shoot over to holdencrazy.com efilive tune library, compare the 7.4l tune to yours to see the differences. The ve tables are in different values tho, may want to try a 8.1l ve table and see how it runs.

good luck

[Oxyacetylene]

I don't have access to a wide band o2 at the moment, but maybe I can find someone to loan me one temporarily. All sensors on the engine are stock. Thanks I will look at the 7.4 tune on that website and see what I come up with.

[hquick]

The MAF numbers will be different.
You'll need to do an AutoVE and then do the MAF.

[Oxyacetylene]

The MAF numbers will be different.
You'll need to do an AutoVE and then do the MAF.

Thanks! I was comparing some different tuning files and noticed that was the big difference. It looks like my next tuning investment will be a wide band O2 sensor. :)

[stroker97k1500]

Here is one tune in the works that was already done with a wideband with stock injectors but a slightly larger cam than stock... but not much bigger
its currently in a 97 k1500 truck and it's a 2000 454 in it with custom wiring harness.

[Oxyacetylene]

Thanks I will take a look at the file. The issues I am having now are: engine tries to stall sometimes when I am cruising along and push in the clutch to stop, and I keep getting a DTC from the IAC system saying the RPM is too high. I need to do more driving to confirm, but the DTC seems to trigger when I am braking while leaving it in gear and not pushing the gas pedal. I am thinking the IAC system is trying to lower the RPM but it can't since it is still in gear? Also I think the stalling issue will be fixed once I get a VSS hooked up, but that may be a little while.

[spastik monkey]

what gauges are you running? The Dakota digital package comes with an electronic vss you could tie into