18 SS 1LE RPM Surges on Idle and out of gear
 

I have a FBO E85 SS 1LE

My car on idle sounds cammed, it isn’t.
Took out E85 and idle sounds much smoother.

However when driving and I’m not in gear the RPMS will surge to about 2K and hold there. They’ll sometimes drop back down after a throttle tap or putting back in gear and releasing the clutch to where it engages. Has anyone else experienced this? Any ideas or solutions?
The car pulls well, stayed beside a Z06 and M3.

You did not list your mods, but a good place to start is to check for vacuum leaks. I had a leak on my MSD where the two halves go together and experienced similar symptoms.

Rotofab, 103MM TB, MSD Manifold, 2” Headers

There is an appreciable chance that your MSD intake manifold is leaking. Myself and others have experienced this leak. You can spray brake clean around the seams and if you hear a sucking sound or the idle drops when you spray, you have found your leak. If you have the ability to monitor your trims, and you have +15% or more short term fuel trims at idle, you have a vacuum leak.

Ahhh, what area did you notice the leak? What was the fix?

The leak was at the rear of the manifold on the right side. The fix was to take the manifold apart and put sealer on the rubber gasket.

I have a roto fab as well soler 95mm TB Think 100 effective and AWE Cat back and it would surge between 2k and 2800k pretty bad. Its an 18 1LE and the manual trans so you feel everything. I bought HP tuners and have been working on my MAF tune and my LTFT have gone from -20 to +- 5 and the surge is gone. Car feel better for sure with just the MAF tuning, taking my time and learning. For 299.00 the scanner and all you can see what the car is doing is worth it IMO.

95mm or larger TB require Torque adjustments for stable idle and no surging. The bigger you go the worse it is.

The car is at the shop now that did the bolt-ons and tuning so I'll update you all when I get it back

I'd feel comfortable hearing that from the people who did the work and everything LOL so if they give it back and say hey this 103MM tb is the reason and it wont cause no harm then I'm good.

103mm sheesh

fwiw my car didn't mind the LT5 tb/msd at all. still drove like stock. i imagine the 103 is a bit much.

Sounds like you have a vacuum leak.

Do you know what your idle spark advance was before and after?

MAF was the issue.