I have a 67 chevelle with a 5.3, turbo and a level 3 4l60e. I’m running the stock pcm with a tune. Also a stock LS9 cam.

I have have an eBay 102mm intake with the 102mm TB that came with it. I am running a AC Delco IAC.

My tuner spent hours trying to hunt down an issue where the engine would idle fine but then start to surge and eventually die. For fun, we unplugged the iac and now it runs fine.

my question is, do you think a 102/102 is too large for a boosted 5.3?

welllll the ecu and harness was from an 02 Escalade. DBW and all. I switched it back to cable TB and wired in all the stuff like TPS and IAC and IAT since this is a SD tune.


the tuner said he tried adjusting the IAC table but it wasn’t making a difference so we unplugged the IAC and all of a sudden the idle was fine.

yes. I adjusted it when the iac was plugged in. Didn’t really help. I adjusted it more and unplugged the iac and now it isles fine. I’m wondering now if the bore for the iac isn’t machines properly so it’s getting hung up or something...

are the Holley efi sniper TBs any good?

I also saw that FItech makes a TB and it looks like it comes with the tps and iac. Those any good?



And lastly, just thought of this.. the iac is from a 02 ls1... is there a difference between a IAC from a 5.3/6.0/5.7?

Did you verify your ECU has the IAC driver chip installed? Some ECUs are DBW only and don’t have the correct hardware to drive an IAC.

the ecu is the 12200411 computer with the red and blue connector

Built a 6liter summer 17’ for my nephew. Ls3 heads and intake. He bought a Holley 92 mm Tb, and the tuner he used spent HOURS trying to get the thing to idle. He (along with many, many others on the interwebz) recommended ditching the Holley Tb. He said he’d machined a couple of them to get the IAC to move properly, to no avail. We tried several IAC’s. Nephew bought a NW 92 mm Tb and the idle was fixed in literally minutes. No kidding.

Really?? Damn well that makes sense about the IAC bore not being right. The NW 92mm might be what I need.

My stock 00 camaro ls1 does the same thing.
I just leave the iac unplugged for over a year.
i haven’t had any issues driving around in cold, heat or with the ac on.
I’m assuming mine is bad and I just haven’t replaced it since it’s working fine as is with my daily.
NW isn’t cheap but it seems a lot of people have had good luck with the cheap tbs they sell.
Holly May just be junk compared to the cheap Chinese ones.
A friend local, got rid of his holly Tb and his issues went away also

This TB I have now came with an IAC and I’m sure it was Chinese because it broke immediately. Did some research and found that tuning wise, AC Delco is the best bet. So I went with that and so I hope it’s not bad... it’s basically brand new!