Vehicle : 2007 Trailblazer SS with over 120,000 miles on it
Original engine 6.2 liter LS2
Transmission : A6

Owner decided to replace the engine with a GM LS3 crate engine with hotcam.
He maintained all the LS2 sensors such as MAF, MAP, PCM, TCM rather than go with the ones used for LS3s.
Owner then had someone tune the PCM, did not tune the TCM for the A6
Owner drove it for some time that way even though hard engine starts and at idle.

Finally he went to a shop to have this fixed. We do the custom tuning so shop owner contacted us to solve and fix the issues.
Shop did testruns with a OBD-II scanner in record mode and then sent us those recording for us to analyze and report the finding
Image below, left side is vehicle as it was running when it went to shop

As seen:
1. Long term fuel trims on average -16-20% too rich
2. Where at idle normal for stock LS3 is around 35 KPA, in this case was around 70 KPA so that meant either some type of vacuum leak or the CAM grind
3. Shop found no real leaks which our data then pointed to the CAM but owner did not know what the grind was.
4. In internet search for this custom LS3 crate engine pointed to the LSA of CAM to be 110, where stock CAM would be around 120 LSA
5. That mean about 50% of the vacuum was lost causing the high MAP readings
6. Analyzing the tune it had we found the tuning changes were way off and some changes were nowhere correct for this engine makeup.
7. So we began by deciding to go back to a stock GM calibration as a clean sheet of paper and custom tuned as to the makeup of the engine and what the OBD-II scanner data was reporting
8. As seen how rich the fuel trims were that scanner data stated the fuel injectors were larger than the last tuner set injector flow to.
9. Due to all the vacuum loss we had to tune 49 different calibration tables that included
• All timing tables for idle, decel, low and high octane gas, cruise, power enrichment and WOT modes.
• All startup tables ( cold, hot, A/C on or off, in park or in gear)
• All idle conditions ( cold, hot, A/C on or off, in park or in gear)
• All functions related to fuel control
• All functions related to airmass, VE, etc
• Redefine all engine conditions as related to MAP and MAF
• Restructure torque and maximum allowed
• Engine knock and misfire tables
• Other functions like coolant fan
• Maximum REV limiter and MPH allowed
• Match the PCM tune then for changes for the TCM control of A6 tranny

Once the shop did several testruns from 3 different levels of tuning we solved all issues and as seen the flywheel HP of 365 and Tq of 329 ft/lbs before our tune increased to 476 HP and 400 ft/lbs ( results on right side of image below) and that was in 90 degree weather and not a very hard testrun so in cooler weather and harder testrun those numbers will get even better

Considering how much weight this SUV has this custom tune should make it much easier to pull the mass
1. Solved all types of startup issues
2. All idle conditions
3. Fuel trims now just about -2% rich
4. Tuning style helped for low vacuum
5. Much better timing from low to WOT
6. Better fuel mileage
7. A6 tranny shifts much smoother and quicker now
8. Almost no engine knock or misfires even when do PE or WOT