Holley Sniper 92mm Throttle Body - Idle Air

[beaufrusetta]

I'm not sure if this is normal or not, but this is my first time really diving in to tuning. I have a 92mm Holley Sniper throttle body on my LS 5.3 (TBSS intake manifold on a Gen3 LM7), and my IAC will drop to 0, and the throttle screw is backed out completely, yet there is still airflow coming through. Is that a normal thing, and I just need to adjust my base airflow to accommodate that? Essentially what I've been doing is to bring down my Base Running Airflow 3g/s, and the idle is a lot more stable. I'm still dropping it lower to even get the IAC to open up while actually sitting at idle. Is that normal?

[Ben Charles]

Sometimes these big TBs let in soo much air, even with the set screw closed all the way it’s too much (I assume It’s stock cam?)

[beaufrusetta]

Sometimes these big TBs let in soo much air, even with the set screw closed all the way it?s too much (I assume It?s stock cam?)

It's a Summit 8712 cam made for more low end (since it's in a Jeep). Specs from a previous thread:

• Engine was built with 209/217 112 lsa mild summit cam (8712), LS6 style valve springs, flat top 4.8L style pistons, TBSS intake manifold, 92MM Holley Sniper TB, 36lb flex fuel injectors (12613411), block hugger headers, catalytic converters deleted, custom 2.5" exhaust to a Borla XR-1 muffler.

[RDF1]

Have you checked for any vacuum leaks?
Never used that TB but ive got a truck here with a 103mm TB on one of them cheap chinese sheet metal intakes and spent quite a bit of time working on getting idle tamed. Found out there was 2 small leaks on the gaskets and one under it on a pipe plug that wasnt threaded in all the way.
Fixed those issues and got it down to 750rpms with a little bit of adjustment left on the throttle stop.

[Alvin]

I'd look for a vacuum leak.

I'd also test "drive" your iac up and down via the scanner. I've seen a lot of bad IAC motors in the past few years.

What is TPS voltage? (sorta indicates blade position)


And just to be clear..

0 IAC counts.. Fully closed.. trying to go lower on idle

160+ Iac counts... pretty much fully open trying to raise idle.

[beaufrusetta]

I'd look for a vacuum leak.

I'd also test "drive" your iac up and down via the scanner. I've seen a lot of bad IAC motors in the past few years.

What is TPS voltage? (sorta indicates blade position)


And just to be clear..

0 IAC counts.. Fully closed.. trying to go lower on idle

160+ Iac counts... pretty much fully open trying to raise idle.

Well, it's definitely not a rogue vacuum leak - I've looked and looked, and can't find one. I did however take the intake tube off while it was idling, and when the IAC is showing "0" (closed), I can put my finger on the IAC port inside the throttle body, and it sucks it right to the hole.

Soooooo...does this mean that it's not closing all the way? Is there some "reset" procedure that can/needs to happen? I've done the throttle reset with the unplugging, koeo, waiting, plugging, koeo.

[Fast4.7]

Well, it's definitely not a rogue vacuum leak - I've looked and looked, and can't find one. I did however take the intake tube off while it was idling, and when the IAC is showing "0" (closed), I can put my finger on the IAC port inside the throttle body, and it sucks it right to the hole.

Soooooo...does this mean that it's not closing all the way? Is there some "reset" procedure that can/needs to happen? I've done the throttle reset with the unplugging, koeo, waiting, plugging, koeo.

It could be the Dodge IAC. Those do not work well with the stock PCM and need to be repinned to even half way work.

[Alvin]

Well, it's definitely not a rogue vacuum leak - I've looked and looked, and can't find one. I did however take the intake tube off while it was idling, and when the IAC is showing "0" (closed), I can put my finger on the IAC port inside the throttle body, and it sucks it right to the hole.

Soooooo...does this mean that it's not closing all the way? Is there some "reset" procedure that can/needs to happen? I've done the throttle reset with the unplugging, koeo, waiting, plugging, koeo.

To me..that indicates that it might not be moving. The PCM sends out pulses to move the IAC motor. There is no guarantee that it moves. You can try commanding it around in the scanner and see if it physically moves (unbolted but still plugged in)

[beaufrusetta]

It could be the Dodge IAC. Those do not work well with the stock PCM and need to be repinned to even half way work.

It's a GM one - I even replaced it today with a brand new one - still sucking air through that port.

[beaufrusetta]

To me..that indicates that it might not be moving. The PCM sends out pulses to move the IAC motor. There is no guarantee that it moves. You can try commanding it around in the scanner and see if it physically moves (unbolted but still plugged in)

I have - it moves...it just doesn't stop airflow at zero

[RDF1]

I had a problem with a 102mm on a 408 that acted weird. 100% IAC and it needed more air to crank. Get it up to temp and the IAC was 0-5% at 700 rpms.
Had to take the IAC out and clean up the bore and set where it was suppose to fit against. After that it fired up great cold and still was able to get it down to 5% hot.

[Alvin]

This sounds like the plunger isn't hitting the stop... OR it could still be a IAC issue. The PCM drives the IAC to a stop.. then counts backwards from it.. There is no guarantee that it actually moves so in short where the PCM thinks the IAC is and where the IAC actually is can be very different.

[beaufrusetta]

This sounds like the plunger isn't hitting the stop... OR it could still be a IAC issue. The PCM drives the IAC to a stop.. then counts backwards from it.. There is no guarantee that it actually moves so in short where the PCM thinks the IAC is and where the IAC actually is can be very different.

Accurate. I pulled off the TB last night and took the IAC out. Turned the key on, and then set the IAC manually to 0. I then put it back in the IAC hole on the TB to see if there was any kind of resistance when I pushed it in...and there wasn't. I'm not sure if this is a common thing, but I'd imagine that when I close the IAC, there shouldn't be ANY air that's coming through. This is nearly a brand new part. I've only put 10k miles on that motor...so it's not like there is gunk built up on it. At this point, do I reach out to Holley? I'm not sure there is anything else I can do...

Or do I just say screw it...because how I've got the tune now, the idle is good...

[Alvin]

If you have no idle issues than I'd let it roll.

Else maybe reach out to holley.. I've not personally had any bad experiences with them but I have had plenty of bad experiences with other throttle bodies. IF i'm sourcing them I always get Nick Williams version.

[beaufrusetta]

If you have no idle issues than I'd let it roll.

Else maybe reach out to holley.. I've not personally had any bad experiences with them but I have had plenty of bad experiences with other throttle bodies. IF i'm sourcing them I always get Nick Williams version.

I've heard the "Nick Williams" brand name a few times recently...but didn't when I was building the motor. I'll have to check them out. I think this issue is more/less just my engineering brain frustrated that it's not working the way it should.

[Fast4.7]

Is this the IAC you have on your Sniper?

https://www.holley.com/products/fuel.../parts/543-105

If it is, that is the Dodge IAC. Standard Products AC416 equivalent that fits a late 90s Dodge 5.9 360. It is pinned differently than the GM IAC and the step count is far different than a GM IAC. When it is pinned wrong it moves to one extreme or the other or just kind of floats not really changing position. I ran it through a sweep from 0-160 counts with almost no movement, then it moved to one extreme and hung in place. Once you get the pinout swapped, one pulse to the stepper motor does not equal the same opening as a GM IAC, even when you swap the pins around. I have set up a few of them and they were a total pain in the rear. Once I was able to equate steps to flow potential, I was able to get it to work halfway well. Personally, I would rather use a Fitech throttle body that uses an OEM GM IAC than the Sniper throttle body. The reason I am clarifying this is I have not seen a Sniper that used a GM IAC unless it is something new.

[village_idiot]

It's probably a badly designed IAC port in the TB itself. I've had several issues out of the Sniper line of TB's that switching over to the Holley Billet unit solved. There's a reason one is $200 and the other is $600

[blindsquirrel]

Will the GM IAC of identical design not fit in place of the 'Dodge' IAC?

[Alvin]

Hot damn.. Just had a car dropped off with one of these. from 0 counts to 300 counts the idle moves maybe 100 RPM.

[gtstorey]

Holley does show a "GM" IAC listed as working for earlier GM vehicles
https://www.holley.com/products/fuel...s/parts/543-34