Hanging RPM's ???

BMGR1 · 12-28-2017, 03:27 PM

So I recently swapped out my stock Intake manifold for an MSD Airforce Intake manifold.

Install went smooth and got everything tightened up..... Now I have a very small issue... Sometimes when I let off the gas, the RPM's hang in the same spot for a couple of seconds and the slowly decline (happens 1 out of 10 times).... or when I go into neutral and coast to a stop, the RPM's hang for a few seconds....

I was thinking it might be the fact that I'm possibly running lean due to all the mods my car has and hasn't been tuned yet. It could also mean a vacuum leak, but my car hasn't thrown any codes for it.

-RotoFab CAI w/Oiled Filter
-Katech Ported TB
-MSD Intake Manifold
-CA Performance Test Pipes
-Stainless Works Catback Exhaust

Any ideas on what it could be?

Racer Ed · 12-29-2017, 12:31 PM

Quote:

Originally Posted by BMGR1

So I recently swapped out my stock Intake manifold for an MSD Airforce Intake manifold.

Install went smooth and got everything tightened up..... Now I have a very small issue... Sometimes when I let off the gas, the RPM's hang in the same spot for a couple of seconds and the slowly decline (happens 1 out of 10 times).... or when I go into neutral and coast to a stop, the RPM's hang for a few seconds....

I was thinking it might be the fact that I'm possibly running lean due to all the mods my car has and hasn't been tuned yet. It could also mean a vacuum leak, but my car hasn't thrown any codes for it.

-RotoFab CAI w/Oiled Filter
-Katech Ported TB
-MSD Intake Manifold
-CA Performance Test Pipes
-Stainless Works Catback Exhaust

Any ideas on what it could be?

My 16 SS does exact same thing, I also have a Katech PTB. W/ stock Intake.
May want to put the Stock TB back on and see if it Fixes it.Hope you can find
the problem.I had my car Dyno Tuned and nothing showed up wrong ???
I will be getting a Pray PTB and Intake soon.
Ed

MP3BOOSTED · 12-29-2017, 01:15 PM

i'm nearly full bolt ons and tuned on e85, i still have insane rev hang, don't really think their is much that can be done to be honest.

AchiliesSS · 12-29-2017, 03:42 PM

Hey guys, I have had the issue since I had my car new, it happens here and there and my car is completely stock. I believe its just a fault in the design or tune, nothing wrong with your car.

Spartan268 · 12-29-2017, 04:22 PM

Quote:

Originally Posted by BMGR1

So I recently swapped out my stock Intake manifold for an MSD Airforce Intake manifold.

Install went smooth and got everything tightened up..... Now I have a very small issue... Sometimes when I let off the gas, the RPM's hang in the same spot for a couple of seconds and the slowly decline (happens 1 out of 10 times).... or when I go into neutral and coast to a stop, the RPM's hang for a few seconds....

I was thinking it might be the fact that I'm possibly running lean due to all the mods my car has and hasn't been tuned yet. It could also mean a vacuum leak, but my car hasn't thrown any codes for it.

-RotoFab CAI w/Oiled Filter
-Katech Ported TB
-MSD Intake Manifold
-CA Performance Test Pipes
-Stainless Works Catback Exhaust

Any ideas on what it could be?

I saw another poster in the general section saying something about loose bolts on the intake and a leak. It didn't throw any codes but half the bolts were missing and some others were loose. There's something in the MSD instructions to tighten again after 1000 miles.

Oil Man · 12-29-2017, 05:16 PM

I'm not modded, but this sounds a lot like what happens when you try to rev the engine during the cold start cycle. Is it like that?

Spartan268 · 12-29-2017, 05:49 PM

Quote:

Originally Posted by Oil Man

I'm not modded, but this sounds a lot like what happens when you try to rev the engine during the cold start cycle. Is it like that?

I believe it's something like this:
https://youtu.be/dHEp5YE2tC4?t=4m20s

SSDanny · 12-29-2017, 06:33 PM

I believe the cars stock tune does this because of emissions. It sucks, but that's what happens with these electric throttle bodies..

A tuner should be able to tune this out according to another member on here.

Oil Man · 12-29-2017, 07:35 PM

Quote:

Originally Posted by Spartan268

I believe it's something like this:
https://youtu.be/dHEp5YE2tC4?t=4m20s

Wow. Ok. That's a more extreme example of what I was thinking of.

BlackbeastSS2 · 12-29-2017, 08:21 PM

I know exactly what it is. It’s a vacuum leak in your manifold.

When I changed over to my Holley high ram, I had a vacuum leak and it sound exactly like the YouTube video that was posted above. I redid my gasket and tighten down the bolts and it was fine.

If you have not modded, then simply check for a vacuum leak with stock intake manifold.

BMGR1 · 12-30-2017, 11:21 PM

It was a vacuum leak at the manifold intake runners.... the 10 outer bolts of my MSD manifold became loose probably from all the vibration and the fact that I didn't use threadlocker on the bolts and was causing a vacuum leak as stated above....

I bought some blue loctite and applied to all the supplied bolts, all good now... Check your manifolds or throttle body bolts to make sure they are tight after 2-3 heat cycles.... It only took my MSD IM bolts 3-4 days to come loose to the point I could undo them by hand

Hope this helps some of y'all

01midmetws6 · 01-02-2018, 10:14 AM

There is also an updated GM calibration file to address hanging idle issues on stock cars. We use the updated cal file on all 6th Gens before tuning to eliminate this issue. The TSB number is #16-NA-074:

12-29-2017, 01:15 PM	#3
MP3BOOSTED Drives: 2017 Camaro SS 1LE (F1A-94 FBO H/C) Join Date: Jun 2017 Location: San Antonio Texas Posts: 844	i'm nearly full bolt ons and tuned on e85, i still have insane rev hang, don't really think their is much that can be done to be honest. __________________ Performance Mods: F1A-94, DSX Flex Fuel Kit, MSD Spark Plug Wires, KOOK 2" off road headers, MBRP Race catback exhaust, Pray Performance Custom Boost Cam, Rocker Arm Trunion Upgrade Kit, 7.850" Hardened Chromemoly Length Pushrods and Johnson Racing 2110R Lifters, TSP CNC'd Heads, Ported MSD intake manifold, 103mm Katech Throttle body, Forged Pistons/Rods, RPM Meth kit, DSX Aux Fuel system, AEM Failsafe and banks gauge, LT4 HPFP, LT4 injectors, BMR motor mounts, Hurst Short Throw, Manley SS exhaust valves Videos of my car? Check here: https://www.youtube.com/channel/UCNi...Qy1OL4NVGlPogw

12-29-2017, 06:33 PM	#8
SSDanny Drives: 2017 Camaro SS M6 Join Date: Apr 2017 Location: LA Posts: 449	I believe the cars stock tune does this because of emissions. It sucks, but that's what happens with these electric throttle bodies.. A tuner should be able to tune this out according to another member on here. __________________ 2017 Camaro SS - Kooks Long Tube Headers 1-7/8th - EFI Flex Fuel Kit - Megan Racing Coilovers - FORGESTAR F14's 20x9.5 & 20x11

12-29-2017, 08:21 PM	#10
BlackbeastSS2 Drives: 2019 Camaro 1LE Shock Candy Join Date: Mar 2016 Location: Garage Posts: 1,798	I know exactly what it is. It’s a vacuum leak in your manifold. When I changed over to my Holley high ram, I had a vacuum leak and it sound exactly like the YouTube video that was posted above. I redid my gasket and tighten down the bolts and it was fine. If you have not modded, then simply check for a vacuum leak with stock intake manifold. __________________ LT4 1.7 Supercharger snout ported & 100% Meth 103 Katech TB, KATECH Custom Heads, DSX In-line fuel TSP Headers, Spec P Super Twin Clutch, TSP EL C7 CAM Diamond Piston & Manley Rods, Roto Fab Big Gulp BTR Push Rods,LS7 Lifters, ARP, FI Chiller, Kirkey Seats SJM Line Lock, Hurst Pistol Grip. 747/739 RWHP street tune - 821/794 RWHP track tune 101 octane. 2014 Mini Cooper countryman S All4 M6 daily driver

12-30-2017, 11:21 PM	#11
BMGR1 Drives: 17' SS 1LE Join Date: Apr 2017 Location: Arleta, CA Posts: 49	FIXED!! It was a vacuum leak at the manifold intake runners.... the 10 outer bolts of my MSD manifold became loose probably from all the vibration and the fact that I didn't use threadlocker on the bolts and was causing a vacuum leak as stated above.... I bought some blue loctite and applied to all the supplied bolts, all good now... Check your manifolds or throttle body bolts to make sure they are tight after 2-3 heat cycles.... It only took my MSD IM bolts 3-4 days to come loose to the point I could undo them by hand Hope this helps some of y'all __________________ 2017 SS 1LE Texas Speed 1 7/8" Longtubes \| MSD Atomic Airforce IM \| Stainless Works Catback w/NPP \| Katech Ported TB \| RotoFab CAI \| E85 (475hp / 476tq) 2015 R1 2003 350z

12-28-2017, 03:27 PM	#1
BMGR1 Drives: 17' SS 1LE Join Date: Apr 2017 Location: Arleta, CA Posts: 49	Hanging RPM's ??? So I recently swapped out my stock Intake manifold for an MSD Airforce Intake manifold. Install went smooth and got everything tightened up..... Now I have a very small issue... Sometimes when I let off the gas, the RPM's hang in the same spot for a couple of seconds and the slowly decline (happens 1 out of 10 times).... or when I go into neutral and coast to a stop, the RPM's hang for a few seconds.... I was thinking it might be the fact that I'm possibly running lean due to all the mods my car has and hasn't been tuned yet. It could also mean a vacuum leak, but my car hasn't thrown any codes for it. -RotoFab CAI w/Oiled Filter -Katech Ported TB -MSD Intake Manifold -CA Performance Test Pipes -Stainless Works Catback Exhaust Any ideas on what it could be? __________________ 2017 SS 1LE Texas Speed 1 7/8" Longtubes \| MSD Atomic Airforce IM \| Stainless Works Catback w/NPP \| Katech Ported TB \| RotoFab CAI \| E85 (475hp / 476tq) 2015 R1 2003 350z

12-29-2017, 03:42 PM	#4
AchiliesSS Drives: 2017 Black on Black 1SS Join Date: Sep 2016 Location: Louisiana Posts: 82	Hey guys, I have had the issue since I had my car new, it happens here and there and my car is completely stock. I believe its just a fault in the design or tune, nothing wrong with your car.

12-29-2017, 05:16 PM	#6
Oil Man Drives: 2016 2SS, 2018 ZL1 A10 (RIPx2) Join Date: Jun 2016 Location: Southern California Posts: 304	I'm not modded, but this sounds a lot like what happens when you try to rev the engine during the cold start cycle. Is it like that?

01-02-2018, 10:14 AM	#12
01midmetws6 Drives: 16 Camaro 1SS A8 Join Date: Dec 2014 Location: St Paul, MN Posts: 7	There is also an updated GM calibration file to address hanging idle issues on stock cars. We use the updated cal file on all 6th Gens before tuning to eliminate this issue. The TSB number is #16-NA-074:

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