I'm new at this and am trying to figure out what to do to improve my cold start situation... I've read enough to only work on one 'area' at a time and thought if I can knock this down then the rest should be a little easier

Vehicle is a 1989 Corvette, 355 with a mild cam and intake/head work, 6-speed trans. Bought it with a bad engine so I don't know history of how it ran beforehand or if there were any running/sensor/computer issues...

I assume it's a '165 PCM (it's a reman so no GM stickers that I found - is there a way to validate this? Is it printed on the board somewhere?) and when I opened it up I found out that it has installed a hypertech 'street master' chip in it to my suprise.

Using that chip I can start it up, it needs throttle to keep running, but once the engine temp gets up around 130* or so it will start to run on it's own without giving it a little throttle to 'help' it and then at 170* or so it'll idle nicely at the target idle RPM.

From doing some comparison I believe the chip is based off of the APYP calibration with only a few changes that doing a compare using TunerPro RT comes up with changes to the Spark advance table and the power enrichment vs RPM and fan temps - none of which are in the lower RPM cells or the colder temps (a couple in the hot cruise and 2400 RPM on up, and WOT 160* up) - none of which should impact the cold start.

I've searched and read here quite a bit on building a raw file for startup, and found some references to where the stock ARAP (auto trans) bin is real rich at startup and I also believe that I need to lean the startup out but what's the best way to verify this without a heated O2 or a wideband O2? Can I datalog the cold start and look at IAC counts to determine where

Do I just take out fuel from the "Startup Enrich Vs Coolant" table? It was about 20*c yesterday when testing this so I'm assuming thats where it started reading the tables.

Looking through some logging I did when it was around 160*f the idle RPM was around 675-725 and the target in the Idle RPM vs Coolant is 800 at that temp so the computer isn't keeping the idle up enough - is there a way to verify that the IAC valve is actually working properly?

IAC was steady at 160 and then at 180*f it drops to 93-105, then at 192* it's pretty steady at 71 - does this mean I need to crack the throttle plate open a little more to compensate?

 

71 at full operating temp is REALLY high, especially if A/C is off.

you should be seeing somewhere in the range of 20-40 at idle when fully warmed.

so, yes, adjust the throttle a bit, until it gets in that range, and it MAY fix your cold start issues.

 

Well I looked through the bigger logfile that I collected and that's about the lowest that I saw - I'm going to fire it up and get it up to operating temp then try this method to adjust the base throttle position and check the TPS voltage while I'm at it: https://www.thirdgen.org/tpimod2

If that's all that it takes I'm going to move on to disabling the EGR/AIR and probably VATS and go on to the part throttle tuning next!