Rough idle
02-02-2012, 09:01 PM
#21
Melting Slicks
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A slight lope at idle, both cold and warm, is normal for the LS3 due to its slightly aggressive cam profile.
If it's beyond slight (barely noticeable), there are a lot of good suggestions above.
To those suggestions I'd add trying a bottle of Techron in the fuel and avoiding discount brands of gas.
If it's beyond slight (barely noticeable), there are a lot of good suggestions above.
To those suggestions I'd add trying a bottle of Techron in the fuel and avoiding discount brands of gas.
02-03-2012, 03:19 AM
#22
Safety Car
Recently bought a 2012 1LT w AT. This simple "bottom of the line" model is perfect for me, and I'm very pleased with it except for one thing.
I can't get used to the rough and low-RPM idle. This idle is best described as "irregular" and it feels like not at all like the "lope" I associate with a high-overlap cam (e.g., an old C1 with a ...097 "Duntov" cam, which had a beautiful lope...but I digress).
My car idles like it has an irregular misfire, but I suspect it is not misfiring (would trigger light, etc.). I can feel the car slightly shudder at irregular intervals. Moreover, I'm astonished at the low RPM at idle. Assuming the tach is reasonably accurate in this range, it reads 500 to 550 RPM at warm idle. Cold idle is also rough and only slightly higher RPM.
I noticed this oddity before I bought the car. Dealer said it's normal and started a couple of other 2012 Corvettes with LS3s to convince me.
Also I've read through lots of prior posts and I know that this subject has been discussed quite a bit. But it seems like some basic questions haven't been answered in a convincing way. So I would appreciate hearing from other LS3 owners and/or general corvette experts on:
1. Is the irregular idle I describe normal?
2. Is 500-550 RPM warm idle speed normal?
3. Has anyone ever got an interesting response from a dealer re C6 LS3 rough idle issue?
4. Perhaps this is esoteric, but what causes the irregular idle I'm describing?
5. Also esoteric: If 500-550 RPM idle is normal (my prior Infiniti G37 coupe idled smoothly at 700 RPM), why does GM set the idle so slow? My guess is maybe it relates to emissions certification and fuel economy rating.
6. If others have had this concern, have they successfully just learned to live with it?
Thanks in advance to all responders.
I can't get used to the rough and low-RPM idle. This idle is best described as "irregular" and it feels like not at all like the "lope" I associate with a high-overlap cam (e.g., an old C1 with a ...097 "Duntov" cam, which had a beautiful lope...but I digress).
My car idles like it has an irregular misfire, but I suspect it is not misfiring (would trigger light, etc.). I can feel the car slightly shudder at irregular intervals. Moreover, I'm astonished at the low RPM at idle. Assuming the tach is reasonably accurate in this range, it reads 500 to 550 RPM at warm idle. Cold idle is also rough and only slightly higher RPM.
I noticed this oddity before I bought the car. Dealer said it's normal and started a couple of other 2012 Corvettes with LS3s to convince me.
Also I've read through lots of prior posts and I know that this subject has been discussed quite a bit. But it seems like some basic questions haven't been answered in a convincing way. So I would appreciate hearing from other LS3 owners and/or general corvette experts on:
1. Is the irregular idle I describe normal?
2. Is 500-550 RPM warm idle speed normal?
3. Has anyone ever got an interesting response from a dealer re C6 LS3 rough idle issue?
4. Perhaps this is esoteric, but what causes the irregular idle I'm describing?
5. Also esoteric: If 500-550 RPM idle is normal (my prior Infiniti G37 coupe idled smoothly at 700 RPM), why does GM set the idle so slow? My guess is maybe it relates to emissions certification and fuel economy rating.
6. If others have had this concern, have they successfully just learned to live with it?
Thanks in advance to all responders.
A little roughness at idle is normal for the LS3 engine.
The only way to convince yourself that YOUR engine is normal is to compare it with others. Which your dealer did.
If you need more convincing, go to your local Corvette Club's next get-together.
Possibly, you have some gasoline that's sub-par or low-octane or an odd formulation.
More likely, you and the car need some get-acquainted "break-in" miles... by 5k miles, I bet your concerns about idle quality are a distant memory.
From another thread:
Are you sure that what you're experiencing is abnormal? These engines do exhibit a noticeable amount of "cam lope", felt as a slight vibration or shake at idle. The phenomenon I'm describing is normal so if it's the same thing you're getting my advice is to leave it alone.
For more info, read the following comparison with the "exotic" V8's in the Audi R8, Ferrari F430, and Aston Martin Vantage: http://www.roadandtrack.com/tests/co...on/v-8-exotics
R&T's conclusion: The LS3 was their favorite V-8.
The LS3 really is that good.
02-03-2012, 09:05 AM
#23
Burning Brakes
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make sure you are using good gas.run the car aggressive also..do not lug the motor.........my idle speed when cold is around 1200 r.p.m's.,warm around 900...........have to go see who built my motor.....
02-03-2012, 12:46 PM
#24
I find if i drive the car with out running it hard it still idles a little rough. When i run it hard it will idle so smooth you almost can't tell it is running. The 2010 Camaro i traded in ran the same way. Rough till you got on it.
02-03-2012, 02:39 PM
#25
Race Director
Camaro/Corvettes pretty much have the same motor and a little rough at idle is normal. If the RPM is steady at 500-600rpm then it is fine. If it is bouncing all over then there is an issue.
02-03-2012, 07:47 PM
#26
Thank you to each of you who replied to my 2/2/12 "More on C6 LS3 'irregular' idle" post. Partially due to your comments, I'm getting more comfortable with the fact that this is the normal LS3 idle. However, due to my age, I still have this instinct to turn the idle-stop screw (nonexistant, of course) a tad to increase the idle to maybe 600 RPM which my (probably completly invalid) instincts tell me would cure the irregular shudder. Perhaps any of you of my generation can understand such an instinct.
That's how mine is. Perhaps some commenters have LS2 engines while the question is directed to the LS3. Mine is an LS3.
03-14-2012, 05:04 PM
#29
Heel & Toe
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LS3 Rough Idle
I've had my new GS for two weeks. It idles rough when cold, and shakes a bit like its mad that I woke it up. Reminds me of my 67 SS-396 back in the Stone Age. I just love it! What a car
04-30-2013, 09:02 PM
#30
Safety Car
Thank you to each of you who replied to my 2/2/12 "More on C6 LS3 'irregular' idle" post. Partially due to your comments, I'm getting more comfortable with the fact that this is the normal LS3 idle. However, due to my age, I still have this instinct to turn the idle-stop screw (nonexistant, of course) a tad to increase the idle to maybe 600 RPM which my (probably completly invalid) instincts tell me would cure the irregular shudder. Perhaps any of you of my generation can understand such an instinct.
04-30-2013, 10:31 PM
#31
Safety Car
I understand your concern,I also am an old GM mechanic and worked tune up for years and the engine miss which I don't consider it to be or cam profile.To me it feels just like a coil or plug or wire break down.I in an older engine would have found it by now, but in these LS3's I think it is in the computer tring to adjust the fuel and sometimes it leans for a second to much and causes a plug to miss fire.I have raced and built many engines and this is not a consistant problem to actually trace it down.I can't get the engine to cause the miss at any pictular time or with consinstancy.I guess going with the crowd on this one is what I will have to do.
05-01-2013, 02:14 AM
#33
Safety Car
02-21-2014, 09:32 AM
#34
Safety Car
Member Since: Jan 2014
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rough idle
My c5 has a slight rought idle at times. I am not familiar with the MAF sensor term, what is it and where is it located, I may try cleaning mine. Thanks
02-21-2014, 02:17 PM
#36
Drifting
The MAF sensor is right up front on the air intake shroud. You have to remove the intake to check the air filter, but no need if you just want to remove the MAF.
There is a special connector on the driver's side - a little clip has to be removed prior to unclipping the connector. I always place a large towel under the connector, because the removeable clip tends to drop down. Then unclip the connector.
2 screws and then you can remove the MAF. This is a very delicate sensor - be gentle when handling or you will be exercising your credit card
.
M....
There is a special connector on the driver's side - a little clip has to be removed prior to unclipping the connector. I always place a large towel under the connector, because the removeable clip tends to drop down. Then unclip the connector.
2 screws and then you can remove the MAF. This is a very delicate sensor - be gentle when handling or you will be exercising your credit card
.M....
03-07-2014, 10:48 PM
#37
8th Gear
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03-08-2014, 12:51 AM
#38
Instructor
I don't think there is a gremlin to find. Ive had two LS2s and one LS7 and all of them have had the rough idle and the occasional shiver. Its more noticeable in the LS7. All were super smooth with some throttle. Its just one of the characteristics of these LS engines. Enjoy!
03-08-2014, 08:24 AM
#39
Safety Car
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Let me know what u find, my 2001 has the same issue. I hate to start messing with it and make it worse but I would be interested in knowing what u find. Keep us posted
