[sniperlif3]

As the weather got colder, maybe below 50 degrees. I have started noticing a rough idle condition with RPM fluctuations by around 100 RPM. Normal idle stays around 650-700 and the fluctuations bring it up no more than about 800 but it is noticeable. Probably happens every 30 seconds for a couple of times then stabilizes.

Also, when coming to a stop and changing from gear into neutral at random times the RPMs stay high even at a complete stop and will stay high for a few seconds. A lot of the time it is around 900-1100 rpm, but have had a few times where it stayed up at 1500.

Both of these happen no matter if the A/C is on or off. I recently took a look at my engine to see if anything was out of place or weird and noticed a popping noise coming from (I believe) inside the intake manifold that coincided with the RPM fluctuation.

It is very inconsistent when either of this situations happen, but I am curious if anyone has some feedback of what to look for. My first thought is that the popping might tell me that my tune might be bad for cold weather and that the popping is a random preignition in the manifold, but other than that I am at a loss. Driving does not feel like it has changed, it only seems to have effected my idle condition.

It is a manual 2021 SS, I have a tune with longtube headers, cat-back, MSD ported manifold, 103mm throttle body, Roto-fab, flex-fuel.

Any pointers or things to look at would be helpful to diagnose.

[sniperlif3]

Forgot to mention, I do have CEL for my exhaust that comes and go's. But I am pretty sure it was because my tuner was not used to the new Camaro and did not know which things to tell the ECM to disregard for the changed exhaust and since he had not worked on the new ECM.
Codes are P0171 System Too Lean Bank 1
P0174 System Too Lean Bank 2
P0430 Catalyst System Efficiency Below Threshold Bank 2

Not sure if that provides any info.

[Eldi Z]

From a very high level view, it seems like there is an issue with the tuning parameters. You would be better off visiting a tuner who has experience with the newer ECMs (Gen. 5 LT GDI engines: 2014+ C7 Vettes, 2016+ Camaros /CTSs)

[sniperlif3]

Thanks. I will try to get another look at it.

[Gunkk]

I'd guess a lean condition and odd idle behavior = air leak. But since it's tuned it could be that too. What does your tuner say?

[Spaceme1117]

All the symptoms point to a vacuum leak. I would check the intake manifold bolts. If I recall, it is common on the MSD intakes that they can work themselves loose.

[Rock-It Man]

If you can go back to factory tune, that's what I would do first.

[sniperlif3]

I am reaching out to my tuner currently to get an idea of when he can get me in with my available work schedule.

[Spaceme1117]

Originally Posted by sniperlif3

I am reaching out to my tuner currently to get an idea of when he can get me in with my available work schedule.

With the MSD, are the 3 center bolts on top meant to be tight enough that the washer doesn't spin. I got it from the a dealership performance shop ported with those bolts installed. They seem decently tight, but the washers do spin.

If the bolts are properly torqued, the washers should not spin. Here is a link to another thread where another Camaro owner had bolts loosen up and it sounds like it was also the center bolts: https://www.camaro6.com/forums/showt...=570962&page=2 Symptoms of their cars sounds very similar to what yours is doing. The popping noise you are hearing is likely the two halves of the manifold separating and coming back together; the center bolts hold the two halves together. Yours are loose.

I have also attached the MSD install instructions. Look a few pages down for the torque specs and make sure to note that it is 75 LB-INCHES. Also, make sure to note that you should torque the bolts and then go over them again as torquing the outside bolts can affect the torque applied to the center bolts. I would go back and for 3 or 4 times just to make sure.

Should be super easy to try re-torquing and if your car is still having problems, then to back to your tuner.

But I bet this is your problem.

If it were me, I would add some blue Loc-tite to the bolts when doing the re-torque.

Just be careful and make sure to use a quality LB-INCH torque wrench.

The popping noise you are hearing is likely the two halves of the manifold separating and coming back together; the center bolts hold the two halves together. Yours are loose.

[sniperlif3]

Yeah, just took a look through, they almost all loosened up from install when I followed the manual for install. Will need to head to the store to get some loc-tite and will redo the whole process, not a pleasant thing to have happen.

Will post back later after I drive a bit to see if that solved the issue.

Thank you for that tip!

Still going to get my tuner to take a look. Maybe by now he figured out the check engine light for modified exhaust on the gen 6.5. Odd that he has never seen the newest gen 6.5 yet, but we do have a TON of truck owners. Most people around here use the chevy dealership performance shop for work like parts and tuning.

Edit: I actually think I did loc-tite now that I think of it. I know I followed the manual and had gotten loc-tite. Oh well. Will do it again.

[Spaceme1117]

If you used Loc-tite previously, you may want to try Vibra-tite VC-3. It is specifically made for shock and vibration applications.

[sniperlif3]

After driving it around after tightening the bolts the idle issues are gone. I have also went to my tuner about the CEL popping up. Everything seems to be fixed.

Thank you so much to everyone that has helped.

BTW, my tuner said he had noticed that some of the newer Camaros he has seen have been having potential wire overheat/failure for the fan wires due to a 90% duty cycle above a certain temp that is not actually that high. He changed the fan profile to 80% duty cycle as he found that was enough to prevent the issue and provide more than enough cooling, but you could adjust more of a curve if you don't want to remove the top end cooling potential. Just a recommendation.

[Spaceme1117]

Originally Posted by sniperlif3

After driving it around after tightening the bolts the idle issues are gone. I have also went to my tuner about the CEL popping up. Everything seems to be fixed.

Thank you so much to everyone that has helped.

BTW, my tuner said he had noticed that some of the newer Camaros he has seen have been having potential wire overheat/failure for the fan wires due to a 90% duty cycle above a certain temp that is not actually that high. He changed the fan profile to 80% duty cycle as he found that was enough to prevent the issue and provide more than enough cooling, but you could adjust more of a curve if you don't want to remove the top end cooling potential. Just a recommendation.

Glad to hear that you fixed your issues and it was simple.