Idling issues after FAST Intake install

[7420NW7TH]

I changed from an LS6 to F.A.S.T. Intake just recently and having problems with the car dying at idle. I adjusted the idle screw on the throttle body and brought the idle up to about 1000-1050rpms. That helps some, but still, when I go into reverse, or when my rpms suddenly falls off, the engine dies. What do I need to do in the tune to correct this.

[ALB]

Hmm might have same problem. I just installed fast 90, nw 90 tb. I have b1 cam 221/221/558/558 /114. I thought it was my cam. I bumped idle to 950 but still seems to be doing it. was going to add some timing down low and not sure what else to try. I didn't think intake was cause of it. I got my idle counts to think 20 range at idle. thought that was just right.

[S2H]

I changed from an LS6 to F.A.S.T. Intake just recently and having problems with the car dying at idle. I adjusted the idle screw on the throttle body and brought the idle up to about 1000-1050rpms. That helps some, but still, when I go into reverse, or when my rpms suddenly falls off, the engine dies. What do I need to do in the tune to correct this.

put the idle screw back and drill a hole in the TB equal to what was on your stock TB...
then check IAC position...if its not in the 60-80ish range with AC off and Fans off when fully warm then drill a larger hole or drill a second hole
once you get the IAC position to 60-80ish then you can tune VE/MAF tables and when that is done you can tune RAF

[7420NW7TH]

put the idle screw back and drill a hole in the TB equal to what was on your stock TB...
then check IAC position...if its not in the 60-80ish range with AC off and Fans off when fully warm then drill a larger hole or drill a second hole
once you get the IAC position to 60-80ish then you can tune VE/MAF tables and when that is done you can tune RAF

I thought that hole looked alittle small. I'll try that, thanks..

[7420NW7TH]

Hmm might have same problem. I just installed fast 90, nw 90 tb. I have b1 cam 221/221/558/558 /114. I thought it was my cam. I bumped idle to 950 but still seems to be doing it. was going to add some timing down low and not sure what else to try. I didn't think intake was cause of it. I got my idle counts to think 20 range at idle. thought that was just right.

Mines a Nick Williams throttle body also. Looks like the hole in the blade is too small.

[WS6FirebirdTA00]

DO NOT BLINDLY DRILL THE HOLE.

Since it is a 90mm TB, there is more open area around the blade for air to pass. This is why Nick did not make the hole so large I would think.

You need to provide us with more info on your setup and some scans/tune information if you want help.

[S2H]

DO NOT BLINDLY DRILL THE HOLE.

Since it is a 90mm TB, there is more open area around the blade for air to pass. This is why Nick did not make the hole so large I would think.

You need to provide us with more info on your setup and some scans/tune information if you want help.

I didnt say to drill blindly
and we dont need any more info on your setup....
you changed intake and TB and suddenly Idle changed..so its intake and TB related...

there shouldnt be any open area around the TB when it is closed....
which is why we need a hole in the TB blade to begin with..
the set screw should be set so that when you let the TB slam shut from WOT that it doesnt stick shut...
thats the intended design of that set screw... its not an idle bleeder like on a carburater

again...all that is needed is to check IAC position with car fully warmed up AC off and Fans Off...
drill the hole until you get it in the 60-80ish range
also do this with the hood open so you can stay clear of heat soak which can skew IAT readings in normal temps which in turn skews the IAC relationship
if you are not in that 60-80ish range....drill a little more
preferrably take steps in 1/64th incriments...or 1/32 incriments at a minimum.

[7420NW7TH]

DO NOT BLINDLY DRILL THE HOLE.

Since it is a 90mm TB, there is more open area around the blade for air to pass. This is why Nick did not make the hole so large I would think.

You need to provide us with more info on your setup and some scans/tune information if you want help.

I'll see what I can do when I get home.

Setup is:

408", 244/249 cammotion cam, 114+4, .630" lift, AFR 225 heads, Ported FAST w/ NW tb, 1 3/4 dynatech headers.

All I did was replace the LS6 with the FAST. It was idling perfectly before the swap. I'll see about getting some logs later...

[WS6FirebirdTA00]

I'll see what I can do when I get home.

Setup is:

408", 244/249 cammotion cam, 114+4, .630" lift, AFR 225 heads, Ported FAST w/ NW tb, 1 3/4 dynatech headers.

All I did was replace the LS6 with the FAST. It was idling perfectly before the swap. I'll see about getting some logs later...

OK, the reason I asked is because in stock form, you should not have had to of touched anything on it.

Also, after taking logs, you may want to check for any sort of air leaks. I have seen several issues with the TB gaskets not being installed correctly. When you take your log, log:

TPS
TPS voltage
IAC position
RPM
STIT
LTIT (in gear and P/N)
Throttle follower airflow

Scott, take a TB, block the hole, and see if water runs through. A closed blade does NOT create a seal around the circumference of the blade, which allows air to pass through (hence the zeros in the IAC effective area table).

If you are going to drill the hole, yes log the IAC FIRST. Do not just go drill the hole to what the other one was, because as I said, it will not be the same on different TB and will be even more off with a different diameter TB.

In the log, give it a rev, try to make the car screw up how you are describing.

[Country Boy]

For a switch to a 90 mm, dont you have to mulltply the table by a certain percentage because of the size difference?

Whats funny, my G5X3 H/C car idled fine with no hole in the TB.

[WS6FirebirdTA00]

yea I had no holes either, each car wants something different though, thats for sure.

I never multiply the effective area table by a value on my car, I set it up for what the car wants/sees.

[7420NW7TH]

Here is a log that I did yesterday. It seemed to idle fine then..

Also, take a look at the tune..

[Russ K]

Looks like your TB screw is turned in too much, as your tps is not staying at 0%. Back off the screw until the tps is at 0%. Then using my idle cfg file, do a cold start scan till operating temp. Don't touch the throttle or move the car while scanning. Then copy the desired idle airflow histogram into your RAF table of the editor. This will get you close, then just fine tune the RAF table to get the STIT & LTIT +- .75 g/sec.

Russ Kemp

[7420NW7TH]

Looks like your TB screw is turned in too much, as your tps is not staying at 0%. Back off the screw until the tps is at 0%. Then using my idle cfg file, do a cold start scan till operating temp. Don't touch the throttle or move the car while scanning. Then copy the desired idle airflow histogram into your RAF table of the editor. This will get you close, then just fine tune the RAF table to get the STIT & LTIT +- .75 g/sec.

Russ Kemp

Thanks, I will give that a try...

[WS6FirebirdTA00]

so why did you not get a lot with the parameters I posted?

[7420NW7TH]

so why did you not get a lot with the parameters I posted?

Sorry about that, I have a family w/ kids, full time job, etc. That log was done the day before I posted this thread. I probably won't get around to it until this weekend due to certain demands on me at the moment....

[7420NW7TH]

Ok, I just have one question: how do you setup your own configuration?

I tried the one posted above, but it didn't work. My car is a '98. I suppose this has something to do with it?

Anyway, I'm trying to setup a configuration like WS6FirebirdTA00 describes above.

I'm not discounting anyones advice, because drilling out the tb may be the way to go. It worked last time when I had a ported stock tb..

I'm just wanting to get some logs first, but have no idea how to create a configuartion..

[ALB]

Update. I drilled out my nw 90 to 13/64. Read some other guys drilled their that much with similar cams. Then played with the set screw until got like 20 to 30 ac off for iac counts. Then reset tps. Car is working great now . 100% better. Also before I installed my fast 90 and NW 90 I had ls6 intake and ported stock tb. I also drilled the hole bigger on that and the cam worked fine. I had no tuning except for maft for fuel. Didn't even hook up the spark part of it. Our crappy max 92 octane don't leave much room for more timing.

Anyway I tried playing with the idle speed and spark at idle. But my cam was surging and running terrible until I drilled out the darn hole. And I set the iac counts to 20 to 30 and then 50 to 60 and nothing worked until did the 5 second hole. You can always put rivet in or get another blade. I did the rivet thing when put the ported stock one back to stock hole size when resold it. Sometimes simple works.

[ALB]

Oh Nick Williams himself recommends drilling out the tb.

[7420NW7TH]

Thanks for the update. I knew it would come to that. I did the same thing on my ported stock tb.

I am having problems getting fuel pressure right now though. I think my fuel pump may have died