Tuner pros, help me out here. Ever since I upgraded my LS6 intake and stock TB to a ported FAST 92 intake and matching 92 TB, my 2002 Firehawk with a mild 228/234 114LSA cam and 241 AI ported heads will turn over, but not keep an idle in a cold start. If it is below 60 degrees and she sits overnight, I can't start the car without holding down the throttle for at least a quarter of the way down for 10 seconds....meaning she needs more air to come through the throttle to get her going. My reputable tuner has tried everything, and he is thinking that the problem is due to the too small idle air port on the FAST 92 TB. He tuned to deliver maximum air and is out of ideas other than swapping out the new FAST 92 to replace with a Nick Williams 90 TB with a better design and larger idle air port to get her to start when cold. The car surges like she is set on cruise control when I cruise through the neighborhood at 30mph, and I'm also occasionally stalling out in parking lots, and she even cut out at me once while rolling 40mph after an engine rev in neutral...scary. He has tried all he knows, and attributes the stalling out due to the VIG 3200 torque converter being too tight and not custom made or geared to my build, as I bought it barely used from someone else that had it for the same LS1 engine...perhaps it is bogging down the engine with too much drag and causing it to stall? Like I said, he tuned, and retuned twice. So...
After two week- long dyno tunes and a mail order tune revision...we are out of ideas. He's tuned over a hundred cars and I know he knows what he is doing. Does anybody have an idea on how to get her idling better and starting in cold weather without mashing down the throttle. This Fast 92 combo is a popular package and I do not have that crazy of a heads and cam package to where it seems as though I should have all these problems. I really don't want to have to swap out and try to sell a new Fast 92 TB, and send in the VIG 3200 for a tweak and re-gear for another $600 for labor and re-gearing fees. I guess the lesson learned is custom build your custom build and don't buy used parts?

So is there anything that we may be over-looking in the tune or is there anyone else out there that had these problems like this? Any other ideas...like drilling a hole in the Fast TB or has anyone tried opening up that idle air hole? I can't stand the unreliable starts and idle. Any help is appreciated!

 

What are your IAC counts during startup?

 

I've been having a very similar issue, with a similar build, except I have a NW 92tb and a M6 transmission. The odd thing is that after I removed my FAST 92 intake to install a -AN fitting with a short hose to attach the MAP sensor better and ported runners on it, it's ran noticeably better but still not perfect.
One thing you can try(until you figure out the actual problem) is to first make sure the tb blade is just opened up enough so the blade doesn't stick, an then open up the tb blade 1 full turn and do a tps reset. This should allow enough additional air in to alleviate some of you start up/idle issues.

 

I hate to just tuner bash because wayyy too much of that goes on in this site but if your tuner is out of ideas you may need to start looking elsewhere. There should be enough adjustment in the throttle body to idle at 1500rpm if you want, I'm guessing the blade wasn't set right after installation. With the car off try adjusting the set screw on the side of the throttle body to open the blade more, work in 1/4 turn increments. After each turn unplug the tps sensor, turn the key to on for about 30 seconds, key off, replug tps sensor and start the car. This may help to make the car more driveable and then you can get everything checked to make sure nothing else in the tune needs touching up. I don't believe the throttle body is the cause of your issues.

 

Do a smoke test to check for vacuum leaks.

 

Post the tune file and some data logs..........

 

Thanks for the advice. I'll see if he can give me the tune file. I'll try the TB blade adjustment when I get the computer back. I sent the computer in for another mail tune revision to him and I am hoping we can get some advice on where he can bump up or down some numbers. Maybe someone who may have had the same issue and changed a setting.
One suggestion from the guys who ported my Intake said, "You adjust cold starts with the cranking/starting airflow table. Increase values in the lower 1/2 of the table by 5%," yet I think he has already tried maxing out the air at cranking.
I've given him the advice from the other posts on here with the IAC levels.
I really do believe he knows what he is doing and I don't want to offend him with obvious advice, or annoy him with suggestions, but I do want a car that starts reliably. Is there anyone out there that found that tweaking one important factor made a huge difference in cold start up and driveability in a case like my setup, which should be fairly common. I never knew tuning was so intricate!

 

I doubt your problem is air -quantity-. Probably more
like a bad idea of air mass. I'd suspect a mixture error
(air leaks) first off since a lot of people seem to be
running into that with aftermarket intakes. If you do
suspect the IAC / throttle then putting the LS6 back
on (if you can find or fab an adaptor) would give you
a diagnostic cut at that (some TBs lack the bleed hole
in the blade, some differ in IAC channel size that does
affect IAC flow, though this should only matter at high
IAC counts).

 

A few things to try. Make sure the VE table is dialed in. Lean out open loop eq table as larger than stock cams will be running in a richer portion of that table due to less vacuum.

IAC counts should be around 60 during a hot stable idle. If so that should be enough IAC range for a cold start.

 

So, no vacuum leaks they checked that since it was ported...said, it would run better at start up if that were the case, and bad when engine warm. This tuner is one of the best, and it's got to be the stall pulling down engine RPMs. He's tried almost everything I've read on here and more, with IAC, Increasing air, increasing fuel. It boggles me that a simple build ike mine can have this many problems even in the hands of an experienced tuner....so all I can say is avoind the combo of parts in my sig unless you have the Torque Converter specifically built for your build and avoid those Fast 92 TB's. That being said, I'll be selling my barely used one soon if anyone wants one. LS6 intake too if anyoner needs one. I guess I am going to send the Vig 3200 back for tweaking, see if that works, and if not, swap out to a Nick Williams TB.

 

This is the problem, THE IAC ON THAT THROTTLE BODY WILL NOT SUPPORT THE SAME AIRFLOW!!!!

Drill a 1/8" hole in the plate and see what that does. Trust me, the total airflow through that hole is not enough to make it work properly. Even stock throttle bodies have holes in the plates. Just do it and be done. You will save you "reputable" tuner a bunch of time and it should be a learning lesson for him.

 

Before you drill anything you need to check what your IAC is at when the car is running and hot. If it's over 100 then you need MAY need to drill a slightly bigger hole in the blade. I had to actually SEAL the hole that came in my PTM 102 throttle body as the machining just wasn't good enough to create a seal without it sticking at idle.

If the TB blade has a hole in it already, I do not believe that cam is big enough to warrant making it bigger.

 

I'm close to you in mods and was looking real hard at the FAST 92mm setup for the future. Will be interested to know how it turns out for you. The FAST TB pic doesn't show the hole, the stock TB does. Good luck.

 

I had to plug the hole in my FAST 90mm to get it work properly. I do not recommend drilling a hole in one to cover up another issue. If it comes to that just adjust the blade so it's cracked open a little.

 

The IAC passageway in the Fast TBs doesn't flow for **** IE the difference between 40 counts and 160 isn't nearly the range as a factory TB.

 

NicD What is your opinion for a better TB with the FAST 92 intake. I'm building my wish list. I like their intake but I don't mind putting a dif TB on there. thanks

 

Interesting, that's the first I've heard of that.

 

Is this a problem that can't be solved with a hand
drill? Open up the inlet bore to the point that the
IAC plunger has flow authority and not the channel?

 

I'd try adjusting the TB blade open first, I don't think the TB is the problem because I'm running a NW92 TB with a similar issue. I've had TB blade opened up 1 full turn on the adj. screw and it ran fine, but I know it shouldn't need to be done that way to get it to start/idle correctly.

 

Agreed. Maybe adjust the throttle opening while data logging IAC counts...shooting for the 30-60 range...then see how it runs after a tps reset. Not the best way to go, but just might get the job done.