LM7 swap tune Help

First time getting into tuning and working on getting my 5.3 swap going. Im hoping for some constructive criticism and help getting in the right direction.

Here's what I've got going;

02 LM7 - 5.3
700R4
BTR stage 2 Truck Cam (Low Lift)
Speed Engineering Shorty Headers
2.5" dual exhaust, Wide band has been ordered and on the way.
8.1 Injectors (Delphi 25343789) Flow rate: 270cc/min (25.5lbs/hr) - 43.5 PSI (Reg set of 55PSI currently)
80mm Throttle Body (Got it for Looks)
Front O2's only.

Ive had to adjust the Idle to get it to run, Also played around with fuel and Spark tables to get it running a bit better. Also I took the VE table to +/- 10-15% by doing some experimenting and it seems like it likes about 5% less. however I did just change my plugs which showed really lean.

Currently It will run and Drive but doesn't like to start right up, I have to pedal it a bit to get it started and get the RPM's to stabilize. On the road it will accelerate ok to start but falls right on its face at any throttle over 33ish %.

I tried uploading my Tune and Log but its not working. Ill update once it works.

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What fuel pressure are you running though?

You can't have 40lb/hr in there if you aren't running that pressure.

25.5lb/hr at 43.5 psi turns into ~30psi at 58psi. I doubt you are running 105psi to reach that 40lb/hr with those injectors.

The other injector data looks questionable too. Find a stock 8.1 tune from the tune repository so you can copy the data over. You need flow rate, min injector pulse, short pulse adder and offset vs volts information.

I bet most of your issues stop once the injector data is correct. I suggest you run 58psi to make things simple. Once injector data is set, never touch it again.


Lots of other stuff is missing from the log. Are you running a MAF?

Add TPS, knock retard, o2 sensors, injector pulse width avg for both banks, cylinder airmass.

Return the VE back to normal too, see what it does with the injector data fixed.

I think I made some progress...at least with the idle.

The idle turned out to a be related to the IAC port on my 80mm throttle body, It was too small and wouldn't let enough air through to start up. I went through and ported out the IAC channel and my "warmed up" IAC steps ended right around 60-80. Where should this be with the Stage 2 cam I have?

I also got my Wideband installed (AEM 30-0300) which was registering 14.6-15.3 at idle. I dont have it logging into hptuners however as I dont have the Pro-link version.

Now what is the best way to proceed? In my mind I would think I need to figure out how to dial in the spark? then dial in the VE via AFR at different RPM's?

Also on the 5.3's is there any way to smooth out the acceleration?

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Look up the "EGR wideband" so that you can log the wideband in HP Tuners on the standard interface. The EGR uses a 5v reference circuit and the wideband has a 5v wire you can use for that. If the EGR is enable in the tune and the wiring is done to the correct pins in the computer harness it will work. There are a few write ups and youtube video's on how to set this all up.

The MAF/VE needs to be calibrated before you start messing with too much timing. The stock timing curves should work good as that fueling is worked on. Don't forget to disable cat over temp protection on this swap vehicle, that will change the fueling on you.

If the MAF is no longer being used, you'll need to disable that in the calibration still. There is another catch to not running a MAF if you are though.


Throttle feel is a tough one. The change in camshaft size, throttle body size and even your torque converter can all play a role in how touchy the pedal feels. It's something you may have to get comfortable with.

I will look into the EGR setup. It makes alot of sense to log the WB....Should have opted for the pro-link, I believe Ive read that it will take more than just buying the prolink cable to actually start logging correct? Would the EGR wiring work if there is no EGR Valve? Im wondering if I was to enable the EGR in the tune if Id be opening up some more issues without having one.

Also, The MAF is still being used. I found out the hard way why its important to have some Straight airflow into the MAF. my initial Fuel trims were all over the board, assuming turbulent airflow and un even flow accross the surface area of the MAF was a big factor.

Lots of Lessons learned on this swap so far.

So long as the EGR codes are disabled and the EGR settings and spark correction tables are disabled, having the EGR enabled will not do anything to how it runs. You are just using the wiring to log the wideband.

Ok, make some progress. I got the AEM Wideband installed and logging through the AC Circuit. Since I dont run AC and my harness has a Pressure Sensor plug and not EGR wires.

I also had to make a few other changes, I went back and forth between the 80mm T/B and the Stock one, I ended up back with the 80mm after porting the crap out of it and boring out the IAC hole. I also had to adjust the throttle cracker and Decay to stop it from stalling while slowing down after its warmed up, which left me with a bit of a hanging idle, I ended up hooking up my VSS up to the PCM which is a work in progress. Im using a 91 NP241 with a 40 tooth gear (I believe) and its still about 120% off of the GPS Speedo.

Whats the best way to Dial in the speedo?
Dropping a hanging idle?
As far as Spark and VE what are the next steps?

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May be a dumb question but can you drill the throttle blade so the idle air isnt having to do as much? I know they already have holes but step then bigger in small increments and watch the iac to see when its not having to do as much? Im a old school carb guy jus trying to learn so if its a stupid question go ahead and bash away

I went through the exact same thought.

The T/B I have came from Summit, the blade was solid with no holes. Some of my research came back that it shouldn't be drilled and the adjuster screw on the side should be used. Others said it should be. The IAC intake hole was very small in relation to the stock and there was a heavy "whistle" when starting up from the air being choked at the IAC.

When I went back to make my IAC hole larger I also went ahead and drilled a hole the exact same size as the stock T/B. I had also played with throttle cracker so i cant say definitively if that made the difference. Now my goal is to adjust the set screw to allow the IAC to be around 50-60 steps when warmed up.

With these changes i was able to drive it to work (1 hr each way) and didn't have any issues (With the idle) I actually think it needs to come down a bit from 800-750.

I think now its just tune VE and Spark, drive it then wait for my 700r4 to give up.

All the gen 3 stuff ive seen have drilled holes i believe so id drill a small one personally but like i said im fairly new to the ls stuff as far as tuning stock type pcms and injection