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Ok guys, hoping someone may be able to lend me a bit of help. I have a 2010 LS3 cammed w/ supporting mods that my tuner and I have been working with trying to finalize tune on. So at 1st after doing initial tune, car ran great, but always seemed to stutter/stumble around 1100-1900 RPM range in all gears, no matter how hard you were in the gas. After tracking down and eventually determining that th O2 sensors and the extension on passenger side were bad, replaced them and that fixed that. After tweaking on tune some more, low gear performance is awesome. Issue now is, is that when cruising in 4th,5th, or 6th gear, around the same RPM range the car shutters under light acceleration. Only goes away after getting up around 2k RPM range. At times, in 6th it even shows some knock retard that pulls timing down. That I have kinda attributed to putting car under a load, even being a light load in 6th gear, but why would it do it in 4th and 5th? I can say that with the old smaller cam that was in before this one and tuned, I did not have this issue. I'm sure its gotta be tune related? Anyone have any ideas? Being tuned using HPT w/ 226/232 58*/59* 112lsa cam, 2" LTH, polished heads, and factory TB and intake. Have inquired over on Camaro5, but havent gotten any responses over there yet, so I was hoping someone over here may have some info for me.
What is the load (grams per cylinder) when this happens?
What is the AFR?
What is the timing like in that area?
A picture of your timing table would be interesting.
I will have to inquire with my tuner on these items. I am in the process of purchasing and installing wideband b/c I eventually am going nitrous, but dont currently run one. Also I just had a surgery couple weeks ago, so haven't been able to get back with my tuner nor been in a hurry to do so yet. I will see if he will shoot me the tune file over for viewing. More or less was just picking some intellectual brains until I could set up another time to meet with the tuner.
My only guess is not enough ignition timing in the RPM/load region where this is happening, just because I made that mistake myself last year. If that AFR is way way off that could do it too. And both are easy to check if you have the data.
I'm sure there are other ways to cause the same symptoms. But without data all we can do is speculate.
I'm pretty sure he did play around with pulling some of the timing out when it was happening due to knock, the last time I was able to meet up with him for some street tuning. Still waiting on him to get back in town from the holidays, but during a trip today, I used my OBD2 Bluetooth device and found this. Looks as if Im still having a problem with my Bank 2 O2 sensor?
So I inspected O2 extension harnesses, swapped O2 sensors and harnesses from side to side, and also hooked up 2 other O2 sensors that I removed back in November. Passenger side continuesto stay consistent at 0.45 as shown in pictures. Checking voltage and ohms with meter yield same readings on both O2 plugs at factory harness and with extensions plugged in. Today with car running, I inspected voltage at factory harness plug on the passenger side only (problem side) and the Ignition voltage (D) read 12-14v, depending on output at time, HO2S Low signal (A) read 15.12v constantly, as well as the HO2S High signal and theHO2S Heater circuit. Also tried to choke out the O2 with car running using a propane tank with just the propane to see if it may make it read, but stayed at 0.45v. And I know heater circuit is working b/c the 2 test O2's I plugged in while investigating were getting hot. Could this possibly be an ECM issue? Anybody have any ideas at all about what I can do to continue troubleshooting
What is the load (grams per cylinder) when this happens?
What is the AFR?
What is the timing like in that area?
A picture of your timing table would be interesting.
Got to talk with my tuner as well. He looked back over the tune and said everything looks ok as it can so far, with exception of the issue. I know its hard to troubleshoot when its not right in front of you. I am going to get all the information I can next time I meet up. He said timing in the area is around 16*-18*, AFR is still to be desired a little but was close at 13.** I think he said. I had it wrote down and have since misplaced it while I was out troubleshooting. Load I cant remember.
You can also try lower airflow in those upper gears.
If Hp tuners ....engine......Base running airflow.......Airflow final minimum and lower it in 4th 5th and 6th
If this happens during light throttle, the timing might be the key thing. At low RPM and light throttle my timing is in the mid-20s.
That said, I kinda wonder if 16-18 is actually the timing you're running at full throttle, which is not what we're talking about here.
If you could post your tune that would clear things up a lot.
Ok, sorry guys its been a few since I was able to sign on. But been talking with the tuner on the issue some more, and he has politely stated he doesn't want to give up the tune file, which I xan understand to an extent. It is his livelihood after all. And I don't mind it too much since he has been more than happy to help me with the issues along the way, and is actively still assisting me, even though I have not been able to get car back to him. But anyway, aside from that, I got the O2 S2B1 working again and actually switching voltage as it should. So the timing at low rpm and light throttle was in the 20's when we started, and we dropped it down below 20's to try and gwt rid of the stutter. I have a couple pics of my drive cycle home that shows couple different spots.
This was in 6th gear, under light throttle and had very slight stutter.
Not sure if these will help that much, and sure they may not, but I can log some other items if needed. I know its not a lot to go on guys, but I appreciate all the responses so far.
You can also try lower airflow in those upper gears.
If Hp tuners ....engine......Base running airflow.......Airflow final minimum and lower it in 4th 5th and 6th
Thanks for response, I am trying to work my schedule out so I can meet back up with him and do some more logging and tuning. The good thing is, is he's not a tune and forget guy, or charging me anymore $$ for any of this. He wants it to be spot on himself.
12-26-2019, 11:42 AM
Upper Gear/Low RPM Shutter 
