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I have owned my 08 Auto LS3 NPP with 48K miles since mid 2019. The car runs great and am very happy with it. I do have a question and can't find an answer on the forum. At idle, there is a slight rumble. Not enough to see the RPM needle fluctuate but just enough where it sounds like a miss and I slightly feel it in the seat. I checked the harmonic balancer and it seems fine. So I checked for stored codes and didn't find anything. But I did see the attached screen shots which show a few "errors/warnings". I tried a couple of other programs with the same OBDII connector and the results are the same. Any idea what these warnings are? I used the same OBD connector and software on my other cars and didn't get any of those warnings. Any help would be appreciated.
I have not detached the battery cables and there were no codes. I did reset the codes a few times with the OBD II connector even though none were present. I'm just wondering if those other parameters won't be checked unless the car is moving and not sitting idle. But like I said, the car runs great other than that very slight rumble. I thought too that it may be the cam they use in the LS3, but don't really know much about that.
When you clear a code or attempt to,it resets all the monitors that you show as not complete.It takes some drive cycles before everything gets set.I think the evap system is usually the last one to complete.
As far as the stumble or miss.probably nothing to worry about.The newer engines have a different firing order and I think that also contributes to the miss you are referring to.Every LS3 I have driven or rode in has the same feeling.
When you clear a code or attempt to,it resets all the monitors that you show as not complete.It takes some drive cycles before everything gets set.I think the evap system is usually the last one to complete.
As far as the stumble or miss.probably nothing to worry about.The newer engines have a different firing order and I think that also contributes to the miss you are referring to.Every LS3 I have driven or rode in has the same feeling.
Thank you. I'll take it our for a drive when the weather here in eastern PA clears a little and see if that settles things down. I appreciate the help. It's probably nothing and me just being OCD...
I have the problem occasionally and an "Italian tune-up" usually fixes the problem. Assuming you drive less than 4K per year that's what I would recommend.
Normal on LS3 because of the firing order. Instead of each bank firing in sequence right bank fires twice in a roll before left bank. You only feel that at idle RPM's
Normal on LS3 because of the firing order. Instead of each bank firing in sequence right bank fires twice in a roll before left bank. You only feel that at idle RPM's
Thank you. Makes sense. And to the other poster, not sure what an "Italian Tune-up" is (and I'm Italian) it may have something to do with zip ties?
Thank you. Makes sense. And to the other poster, not sure what an "Italian Tune-up" is (and I'm Italian) it may have something to do with zip ties?
Thanks again.
That is doing few full throttle pulls to max RPM or to drive it at high rpms ( once fully warmed) to clean up carbon from cylinders and the spark plugs. It could help if the car is driven gingerly for a long time.
Check your plug wires... Sometimes the connector at the end of the spark plug wire gets loose or rusted causing a miss but not enough for the car to throw a code. Don’t forget to check the other end of the plug wire; connection to the coil.
Car is a 2008 so may be time to replace the plug wires.
Most common wire/ plug issue is cylinder number 8 or 6, far rear passenger side. Pretty common in my experience with LS engines.
Last edited by NofakeJake; Jan 31, 2021 at 11:38 AM.
Thank you. Makes sense. And to the other poster, not sure what an "Italian Tune-up" is (and I'm Italian) it may have something to do with zip ties?
Thanks again.
That's a term from the '70's. (I'm getting old.) In those days (none had ever seen a Ferrari, BTW), the story was if you drove a Ferrari around town then eventually it would start to misfire and carbon up. So the solution was to go out and drive it fast and wind it out in the gears. That was an Italian Tune-up.
Now it was probably more of an excuse to go beat on our Chevy's, but it does actually work somewhat.
An 08 with 48k, I'd suggest at bare minimum, unplug, inspect, lube, replug all the plug wires,
Run it down to 1/4 tank, throw a can of Seafoam or Techron in the tank, run it till 'low fuel' warning (cleans up injectors)
Clean the throttle body, over time it gets black gunk on it, can really affect idle quality... not from a Vette but can look like this. It usually just wipes off, don't even have to take it off the car.
I do the above every 25k on all my cars just as routine maintenance, not much work, sure won't hurt.
good luck!
I had the same problem on 2012 Callaway. I checked it with my HP Tuner software and couldn’t find anything. It only had 12,000 miles on it. I changed the wires and put on a set of Granatelli high voltage coils. Idles like a dream and gained a good bump on the MPG as well.
That's a term from the '70's. (I'm getting old.) In those days (none had ever seen a Ferrari, BTW), the story was if you drove a Ferrari around town then eventually it would start to misfire and carbon up. So the solution was to go out and drive it fast and wind it out in the gears. That was an Italian Tune-up.
Now it was probably more of an excuse to go beat on our Chevy's, but it does actually work somewhat.
Same thing on the '69 Porsche 911S my neighbor owned. I remember reading in his owner's manual for the "S" model to do this in order to blow carbon off of the plugs. It said that constant "easy" driving around town was not good for it. I was always up for a "tune up" day with him!
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Slightly Rough Idle
