Ok guys, first off I appreciate any advise on where to start. I recently picked up a 2000 C5 A4, Mods are 383 LS1, TFS 215 cnc Heads, Unknown Cam (told stage 3 TSP possibly), Fast LSXR102, Stock TB, Longtubes Offroad-Back, 3:15 rear, Unknown if converter or not.

I picked up the car an hour from home (we both met in the middle so car was operating temp), ran decent, started and idled fine, no stalling, no stoplight issues.

However next day, about a 50 degree morning tried to start it and there was zero chance without a LOT of pedal to get it to fire off and keep running til it could collect itself.

I intend to buy HP Tuners and get into it a bit myself. Could anyone direct me the best tables to review first? Oddly it seems to run pretty strong otherwise. Which I find funny cause how are you gonna tune the car well enough to drive well but not cold start?

Thanks in advance!

 

Lots of cars are "tuned" good enough to run well at normal operating temps, because most engines can be wildly out of tune and still run "good enough". Once you get Hptuners, post your file and we will be able to see what sort of mess you are looking at. Remember that the factory corrections are active at normal temps, but not at startup, so they can cover up a lot of problems.

 

Imagine you tune cars for a living. Customer arrives at your shop with a car that's fully warmed up from the drive to the shop... You do your thing... Customer drives home... The car never cooled down, so there was never an opportunity to see how the car starts and runs when cold.

Anyway, there is a fair chance that the problem is in one or both of these two tables:



The numbers on the left columns are coolant temperature. Stock C5 values are shown in the tables. The screenshot is from Tuner Pro.

The engine needs more airflow to idle when cold, so if the tuner didn't increase those values enough then that might be the whole problem.
See how much airflow your car needs to idle when warm, see how much higher that is than stock (10% more? 20% more?) and if the cold values have not increased by the same amount, bump them up.

I think HPTuners might call the "Desired Airflow" table something else, maybe "Base Running Airflow" ? Someone who uses HPT will keep me honest here.

You didn't mention what throttle body the car has, but that's another key ingredient. There's a table called "ETC Scalar" (ETC Scaler?) that tells the PCM about the relationship between throttle blade position and throttle opening area, and that might need to change as well. Different throttle bodies require different values. If you have an LS2 throttle body, a web search for "LS2 throttle body ETC scalar" should get you moving in the right direction.

Or try Claude or some other AI, but be sure to double-check whatever they tell you - they're confidently wrong in many cases and they will cite sources that don't support their wrong answers.

Finally there are a couple tables that give the PCM much more information about the blade-angle / opening-area relationship - they have blade angle in one column and opening area percentage in the other column. They're not well documented and I'm not sure HPT even allows you to edit them. I had better luck with my LS2 throttle body with edits to those tables, and my Katech 103mm throttle body would be unusable without edits to those tables. But hopefully that's not necessary.

 

All valid points! Thanks guys I look forward to looking into this with my own software for sure.