I'm about to lose whats lift of my hair!, cold starting issues with 416 LS3 and E67.

[Kamaro]

Please help me before I lose the little hair that is still on my head!, I have this issue for many weeks now with no solutions so far. I got a '71 Firebird Formula with a LS3 based 416 and a GM engine controller kit (part number 19354332), I got the car tuned by a friend of mine using EFI Live (where I live there are no professional tuners for GM cars), the car ran great and got pretty good numbers on the dyno, the issue I have now is the cold start, sometimes it will never start what so ever, sometimes it will run for half a second and then die and will keep doing this for 5 or 6 times in a row before it run poorly for another 5-6 minutes, and during that it will choke and die if I give it some gas. it will finally be ready to drive when it picks up some coolant temp. The dude that did the tune had a look at it and said everything seems fine and I should look else where. since then I removed the whole engine harness and installed it again after cleaning all the connectors and adding a few more ground straps. still no change!, I have attached two log files, one when its cold and hesitate to run, and the other when its running but won't repond well to the gas pedal, and also attached the tune file. This is not my first LS swap, so I do know my way with these cars.

Engine specs :

LS3 block, with 416 rotating assembly
PRC 237 Cathedral port heads - 11.1:1 CR
Camotion Torquey Stroker camshaft - 234/242 @ .621"/.604 -114 LSA.
FAST intake with NW102 DBW TB.
Magnum T56 6 speed.

[10_SS]

Please help me before I lose the little hair that is still on my head!, I have this issue for many weeks now with no solutions so far. I got a '71 Firebird Formula with a LS3 based 416 and a GM engine controller kit (part number 19354332), I got the car tuned by a friend of mine using EFI Live (where I live there are no professional tuners for GM cars), the car ran great and got pretty good numbers on the dyno, the issue I have now is the cold start, sometimes it will never start what so ever, sometimes it will run for half a second and then die and will keep doing this for 5 or 6 times in a row before it run poorly for another 5-6 minutes, and during that it will choke and die if I give it some gas. it will finally be ready to drive when it picks up some coolant temp. The dude that did the tune had a look at it and said everything seems fine and I should look else where. since then I removed the whole engine harness and installed it again after cleaning all the connectors and adding a few more ground straps. still no change!, I have attached two log files, one when its cold and hesitate to run, and the other when its running but won't repond well to the gas pedal, and also attached the tune file. This is not my first LS swap, so I do know my way with these cars.

Engine specs :

LS3 block, with 416 rotating assembly
PRC 237 Cathedral port heads - 11.1:1 CR
Camotion Torquey Stroker camshaft - 234/242 @ .621"/.604 -114 LSA.
FAST intake with NW102 DBW TB.
Magnum T56 6 speed.

Well when engine is cold and just started running your coolant temp is 93 degrees and your Commanded AFR is 14.7... so it looks like it basically has no cold enrichment at least at idle. (no choke), I would expect it to die and run like crap. Then where it looks like you floor it (map goes to 99kpa) commanded AFR is down to 12.75AFR... that might be PE fuel, hard to say. As it warms up, it probably starts running normal just like a carburated engine with no choke.

I just checked my cold start logs (well warm) and sure enough, my stockish LS3 at 93F coolant temp shows 11:8 AFR when running, so start there see what happens. AFR at startup also depends on engine runtime.. in that log I started it right at 93F coolant temp and first few seconds of runtime was 11.8AFR, other times if I start from colder like 60F, then by the time it's at 93F then AFR is 13.9AFR... I woudl try stock values in these tables to start, then richen them up if it still doesnt start good. It's probably all realated more to Intake Valve Temp (IVT) than coolant temp since a hot Intake Valve will vaporize the fuel, a cold one wont.

When I installed the Whipple on my stock LS3 I had lean conditions after startup and take off when coolant was 45-70F... RPM would come up on start like normal then it would almost stall, then takeoff would kickup a bit.. I richened up this area 20% and inta-fix.. smooth startup no RPM drop, smooth takeoff. This was after months of playing with Startup Airflow tables to no avail. Not sure why I needed to do it, didnt have a problem before WHipple.

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Well when engine is cold and just started running your coolant temp is 93 degrees and your Commanded AFR is 14.7... so it looks like it basically has no cold enrichment at least at idle. (no choke), I would expect it to die and run like crap. Then where it looks like you floor it (map goes to 99kpa) commanded AFR is down to 12.75AFR... that might be PE fuel, hard to say. As it warms up, it probably starts running normal just like a carburated engine with no choke.

I just checked my cold start logs (well warm) and sure enough, my stockish LS3 at 93F coolant temp shows 11:8 AFR when running, so start there see what happens. AFR at startup also depends on engine runtime.. in that log I started it right at 93F coolant temp and first few seconds of runtime was 11.8AFR, other times if I start from colder like 60F, then by the time it's at 93F then AFR is 13.9AFR... I woudl try stock values in these tables to start, then richen them up if it still doesnt start good. It's probably all realated more to Intake Valve Temp (IVT) than coolant temp since a hot Intake Valve will vaporize the fuel, a cold one wont.

When I installed the Whipple on my stock LS3 I had lean conditions after startup and take off when coolant was 45-70F... RPM would come up on start like normal then it would almost stall, then takeoff would kickup a bit.. I richened up this area 20% and inta-fix.. smooth startup no RPM drop, smooth takeoff. This was after months of playing with Startup Airflow tables to no avail. Not sure why I needed to do it, didnt have a problem before WHipple.

what table did you make the 20% Adjustment to make it start up smoother and fix the kickup on take off? im having the same issue with my car after supercharger install.

Thank you.

[10_SS]

what table did you make the 20% Adjustment to make it start up smoother and fix the kickup on take off? im having the same issue with my car after supercharger install.

Thank you.

I ended up fixing this, but I don't remember the exact setting that did it, I think it was actually two different tables, one for Open Loop and one for Closed Loop, this is why at first it seemed fixed, then I would see it other times at random. This is because sometimes it's in Open Loop when it happens, other times it's in Closed Loop when it happens, so both may need to be adjusted.

If your in Open Loop and this happens then adjust this table according to IVT temps when it is happening: 12441

Once it switches to closed loop, which stock does very quick, I don't think there's too much you can do with AFR since 02's are trying to take over, so delay closed loop some by adjusting these tables: 12461 and 12462 02 sensor closed loop control.. delay these a bit when cold