Zero2Sixty

I recently installed the LSX intake/TB a month or so ago and I'm experiencing some erratic idle issues. The car turns over no problem, however I have to apply minor throttle to keep it running (else it turns over and immediately dies when cold). After about 30 seconds the car seems to idle (DIS=800; LS1edit) fine. Now here's the problem (erratic), when I begin driving and I approach a stop the car begins to surge between 400-1100 rpm until it stalls. Now what I've been doing is performing the idle re-learn which seems to hold for a little while but I really have to stop slowly at lights/stop signs or it intermittenly stalls again. Of course once it stalls and is restarted its really pissed and requires another idle relearn.

I haven't had a chance to have it re-tuned but is this really a tuning issue ? Is it possible the IAC is bad (car only has 9000 miles on it) ? When I installed the TB I verified that the blade completely closes so any ideas would be appreciated.

Thanks....

Here's a list of the setup:
A4
AS Stage 1x 5.7ltr Heads milled .030
TR224 563 on a 114
Nate's Billet Fuel Rails
Stock Injectors
78mm LSX Intake
78mm LSX TB

Slowhawk

iTrader: (12)

Sounds like an air leak or tuning problem.

dand35th

I have mine.. but 90mm.. so that the throttle blade screw is from 1.25-1.5 turns in... from closed completely.. and any less, does what you describe

Dustin Butts

iTrader: (5)

https://ls1tech.com/forums/showpost....9&postcount=28

Check this post out. Mine was doing that too. 90mm TB and LSX intake.
Check these mechanical things first for binding or that loose bearing. Then check your IAC counts and yes check for vacuum leaks. After all that then get her tuned.

Zero2Sixty

Thanks to those that replied... I'm pretty positive its not a leak since all the seals are new and all the bolts were torqued to spec and later checked again.

Dustin Butts : I'll check the mechanical and the reading on the IAC, a big thanks for posting the link and excellent write-up. I'll post back my results tomorrow.

Andy

Zero2Sixty

Ok, I pulled some stored data runs (idle) I had sitting on my laptop - before and after the LSX intake/TB. My IACP (idle air controller position) counts are as follows:

Before LSX Intake/TB:
range is 22-30

After LSX Intake/TB:
range is 89-95

So whats causing the counts to read higher ?

dand35th

you try to close the TB blade screw a 1/2 turn yet.??.. those readings at idle?? in park or driving?

Zero2Sixty

I wont be able to work on the car till tomorrow.
Both readings were taken @ idle

JEB99TA

iTrader: (32)

Mine does the exact same thing since my cam was installed. Crank at first and idels at 1000-1200 rpm and then after about 10 seconds, it drops down to 700 rpm and surges real bad. It dies once or twice ... only does it on cold starts and at stopsigns and stoplights.

Before my cam install, on cold starts, it wouldn't surge at all, however, it would choke down like it was going to stop running when I'd pull out ... only for about 5 seconds, then, it would run fine.

I changed my fuel filter and injectors and it didn't seem to help much, if any at all ... for what it's worth. It would be nice to know what this is. Think it would help to drill out the throttle plate a little bigger than the factory hole?

Ragtop 99

iTrader: (7)

Low IAC counts reflect more Air getting in. High IAC counts often indicate that not enough air is getting in. I'd try opening the blade as suggested above.

dand35th

yeah need to open the blade to bring the iac's down, it will help any surge also, but if there is throttle hang , then you need to tune some other stuff...

Zero2Sixty

Didnt get a chance to test anything today, guess it will have to wait till the weekend.
Thanks Ragtop for the explanation of high/low IAC counts, I searched and couldn't find an explanation...

JEB99TA, has your car ever been tuned via LS1edit ?

Mike K.

also you want to get the IAC counts right around 30 or so if possible. adjust the TB until you can do this.

JEB99TA

iTrader: (32)

It was dyno tuned when the cam was installed. The tuner said that he changed one of the tables that should either fix the problem or at least make it better. He told me if it didn't totally go away, he would change the same table, which hopefully would fix it. After it did not help and after my max RWHP/PWTQ numbers fell each time it was tweaked/dyno'd, well, I decided not to go back and have it 'tweaked' anymore.

Since he changed whatever he changed and there was no difference, it doesn't seem to be a tuning problem. The !EGR and !AIR were both removed and disabled by the tuner.

Solid346

i am having the same problem with my Solid roller. the car have been built and tuned by Allen Futral. but the same problem, we couldnt fix it. Allan told me straight out, the fast throttle body is piece of ****. the car is been shiped overseas as we speak, but is there a way to fix it when i get it. i dont want to spend another ~$500 on something that doesnt work

Pro Mouse

iTrader: (15)

Ageed!I have the Fast 90mm TB and that thing is complete junk!Mine was tuned by APE and we can not get the idle right.The blade was hanging up in the body and moving on the shaft so the tps had no idea where it was,car didnt want to start and would idle 1500-2000 rpms.I am sending mine back to Fast ,serious quality issues.I have a TPIS on the way,I hope it is much better...