Rough idle on a LS3
03-23-2018, 06:03 PM
#21
Race Director
Dielectric grease is designed to prevent corrosion on the electrical contact, not to make boot stay on. The correct way to install is to "burp" the boot once installed by slipping something like a bent paper clip underneath while installing to allow the air an avenue to escape, then remove. People put dielectric grease on boots to make them easier to remove, not to keep them on. Grease on rubber doesn't make it stick, it makes it easier to slip off.
03-23-2018, 06:37 PM
#22
Safety Car
Dielectric grease is designed to prevent corrosion on the electrical contact, not to make boot stay on. The correct way to install is to "burp" the boot once installed by slipping something like a bent paper clip underneath while installing to allow the air an avenue to escape, then remove. People put dielectric grease on boots to make them easier to remove, not to keep them on. Grease on rubber doesn't make it stick, it makes it easier to slip off.
Last edited by irok; 03-23-2018 at 06:39 PM.
03-23-2018, 06:43 PM
#23
Race Director
03-23-2018, 08:58 PM
#25
Le Mans Master
I am the one that posted about the alternator cable introducing RF into the coil circuit causing intermittent misfires that I felt as a small shake at idle
These misfires never once set off a CEL but were detectable with my TECH ll. Small intermittent and not limited to any one cylinder, I replaced wires , plugs , swapped coils and nothing changed until.......
I moved my alternator battery cable 10 degrees one way and my spark plug cable 10 degrees the other....no more misfire at idle ...
Dave
03-24-2018, 01:26 PM
#27
Race Director
LS3 in the Vette does idle slightly rough in most cases. Kind of like a loping cam feel but mild. Mine idles at 500rpm though. The 6.2L we had in our Denali idled smooth but it also had 20 less HP.
LS3 may be noisy especially when cold.
LS3 may be noisy especially when cold.
03-24-2018, 09:29 PM
#29
Burning Brakes
Idle's Rough
There's plenty of info on this forum about idle . I purchased my 2008 C6 Z51 A/Trans at the end of January this year. I test drove Five (5) different ones of them all either 2008 or 2009. They all idled around 500 or so RPM's when warmed up. First thing is this is a small block chevy pushing 430 or so HP. One person might think it's very rough idle and other's might think it's smooth as silk. I went down to the Chevrolet dealer and spoke to a friend who was their number one Corvette Tech. He said if everything is in good shape. Wires / Plugs and all that. Keep in mind the idle is controlled by both ECM (Engine Control Module) can also be called PCM (Power Control Module) and TCM (Transmission Control Module) if yours is A/Trans. Typically when starting engine cold idle is around 750-800 RPM's When hot 195-200 Degrees (f) or 90-91 Celsius idle should be around 525-550 RPM's in gear. a miner roughness is normal. Listen to the exhaust if you don't hear a miss you should be all good. If the roughness continues above idle then something is wrong. Last of all there is a relearn procedure posted on this forum.
03-25-2018, 12:17 AM
#30
Le Mans Master
If i wear a pair that is hard to remove then that is what a boot jack is for. here in Texas every man should have one at the end of his bed.
03-26-2018, 03:18 PM
#31
Did you replace that rather pricey engine air filter? I just replaced mine at the recommended 50,000 miles and it was $114.00US
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hphammer (03-31-2018)
03-26-2018, 03:23 PM
#32
Intermediate
Thread Starter
Yes, of course. But I've put a K&N filer, instead of OEM one. It is a replacement, that goes in the original airbox and not a whole new intake.
I am also thinking about the fuel injectors. We cleaned them with ultrasound, but not sure if that's enough...
We also moved the alternator cable away from the spark wire N1 as someone here advised, but still nothing...
I am also thinking about the fuel injectors. We cleaned them with ultrasound, but not sure if that's enough...
We also moved the alternator cable away from the spark wire N1 as someone here advised, but still nothing...
03-26-2018, 11:23 PM
#33
Le Mans Master
Not always ... you have to reach a threshold before a CEL is set ...
I am the one that posted about the alternator cable introducing RF into the coil circuit causing intermittent misfires that I felt as a small shake at idle
These misfires never once set off a CEL but were detectable with my TECH ll. Small intermittent and not limited to any one cylinder, I replaced wires , plugs , swapped coils and nothing changed until.......
I moved my alternator battery cable 10 degrees one way and my spark plug cable 10 degrees the other....no more misfire at idle ...
Dave
I am the one that posted about the alternator cable introducing RF into the coil circuit causing intermittent misfires that I felt as a small shake at idle
These misfires never once set off a CEL but were detectable with my TECH ll. Small intermittent and not limited to any one cylinder, I replaced wires , plugs , swapped coils and nothing changed until.......
I moved my alternator battery cable 10 degrees one way and my spark plug cable 10 degrees the other....no more misfire at idle ...
Dave
03-27-2018, 12:31 AM
#34
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Yes, of course. But I've put a K&N filer, instead of OEM one. It is a replacement, that goes in the original airbox and not a whole new intake.
I am also thinking about the fuel injectors. We cleaned them with ultrasound, but not sure if that's enough...
We also moved the alternator cable away from the spark wire N1 as someone here advised, but still nothing...
I am also thinking about the fuel injectors. We cleaned them with ultrasound, but not sure if that's enough...
We also moved the alternator cable away from the spark wire N1 as someone here advised, but still nothing...
Immediately changing stuff on a used car isn't always beneficial, especially when you don't use OEM replacements. It might have been a prudent thing 50 years ago, but not anymore. Most of what you "replaced" are components that are designed to last 100,000 miles or more. I still have the original hoses, plug wires, PS fluid, O2 sensors, pullies, water pump, etc at 152,000 miles with no fear of a near future failure. It's more likely you'll need wheel bearings, rotors, and brake pads before 100K miles than most of what you replaced.
03-27-2018, 12:42 AM
#35
Hi all, I have just bought a '08 base Corvette. Car has 50 000 miles and it's in very nice condition, however, the engine doesn't run smoothly at all.
Whenever I buy a new car I like to change everything under the hood - liquids, spark plugs, spark wires, pumps, filters, 02 sensors, belts, rollers, water hoses and so on, so I can try to guarantee myself more or less trouble-free ownership of the car.
So I thought that changing the 02 sensors and the spark plugs/wires will solve this problem. However, after doing this, there is absolutely NO change in the way the engine idles. It's like there are little misfires all the time and that obviously translates in vibrations on the whole car.
I have saw many threats in this forum from people that had the same issue on their C6's - some people say it's normal, some say their engines are working as a swiss clock. I also doubt that the car has been working like this in the showroom, so it must be an issue somewhere. However, I haven't seen anyone to say what was causing his problem, so I decided to open this thread and get some opinions.
The main issue is that I live in Bulgaria and here these cars are not very common and unfortunately my mechanic doesn't have a clue where should he look for the resolution of this problem.
OBDII diagnosys doesn't show any errors either. The only issue with the car when I got it was that after a collision with a curb, the front right wheel was little off position, but it was a very light hit, so after some suspension alignment, everything was put back in place.
Any help will be highly appreciated guys.
Whenever I buy a new car I like to change everything under the hood - liquids, spark plugs, spark wires, pumps, filters, 02 sensors, belts, rollers, water hoses and so on, so I can try to guarantee myself more or less trouble-free ownership of the car.
So I thought that changing the 02 sensors and the spark plugs/wires will solve this problem. However, after doing this, there is absolutely NO change in the way the engine idles. It's like there are little misfires all the time and that obviously translates in vibrations on the whole car.
I have saw many threats in this forum from people that had the same issue on their C6's - some people say it's normal, some say their engines are working as a swiss clock. I also doubt that the car has been working like this in the showroom, so it must be an issue somewhere. However, I haven't seen anyone to say what was causing his problem, so I decided to open this thread and get some opinions.
The main issue is that I live in Bulgaria and here these cars are not very common and unfortunately my mechanic doesn't have a clue where should he look for the resolution of this problem.
OBDII diagnosys doesn't show any errors either. The only issue with the car when I got it was that after a collision with a curb, the front right wheel was little off position, but it was a very light hit, so after some suspension alignment, everything was put back in place.
Any help will be highly appreciated guys.
* I call it an "irregular" rather than a rough idle because rough idle often implies a cam lope idle. Having owned Corvettes with 097 and 30/30 cams, I can tell you this is nothing like a cam lope idle. My guess is that this irregular idle is associated with the fact that the LS3 warm idle is a relatively low 500-550 RPM in order to get a slightly better fuel economy score (affecting CAFE) because the test cycle has some idle phases.
My suggestion: Unless it's clearly a misfire e.g. due to plug wire shorting, quit trying to fix it and just get used to it.
03-27-2018, 06:49 AM
#36
Le Mans Master
03-27-2018, 06:51 AM
#37
Intermediate
Thread Starter
That K&N may be causing you a problem. It does a poor job of filtration and has a reputation of being over-oiled even right out of the box, which wreaks havoc with the MAF. If you didn't throw away the OEM filter, put it back on and clean the MAF.
Immediately changing stuff on a used car isn't always beneficial, especially when you don't use OEM replacements. It might have been a prudent thing 50 years ago, but not anymore. Most of what you "replaced" are components that are designed to last 100,000 miles or more. I still have the original hoses, plug wires, PS fluid, O2 sensors, pullies, water pump, etc at 152,000 miles with no fear of a near future failure. It's more likely you'll need wheel bearings, rotors, and brake pads before 100K miles than most of what you replaced.
Immediately changing stuff on a used car isn't always beneficial, especially when you don't use OEM replacements. It might have been a prudent thing 50 years ago, but not anymore. Most of what you "replaced" are components that are designed to last 100,000 miles or more. I still have the original hoses, plug wires, PS fluid, O2 sensors, pullies, water pump, etc at 152,000 miles with no fear of a near future failure. It's more likely you'll need wheel bearings, rotors, and brake pads before 100K miles than most of what you replaced.
Last edited by rumen1; 03-27-2018 at 03:41 PM.
03-27-2018, 06:56 AM
#38
Le Mans Master
Dielectric grease is designed to prevent corrosion on the electrical contact, not to make boot stay on. The correct way to install is to "burp" the boot once installed by slipping something like a bent paper clip underneath while installing to allow the air an avenue to escape, then remove. People put dielectric grease on boots to make them easier to remove, not to keep them on. Grease on rubber doesn't make it stick, it makes it easier to slip off.
The burping is the secret most people miss.
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Corvette_Ed (03-27-2018)
03-27-2018, 07:07 AM
#39
Le Mans Master
Dielectric grease is non-conductive and can work as an insulator especially in low voltage situations. Here is a quote:
Dielectric grease is a nonconductive grease. Because it is nonconductive it does not enhance the flow electrical current. Electrical conductors should not be coated with dielectric grease prior to being mated. However, dielectric grease is often applied to electrical connectors, particularly ones which contain rubber gaskets, as a way to provide a nonconductive lubricant and sealer for the rubber portions of the connector.The widest use of dielectric grease is in high-voltage connections associated with spark plugs. The grease is applied to the rubber boot of the plug wire. This helps the rubber boot slide onto the ceramic insulator of the plug. The grease also acts to seal the rubber boot, while at the same time preventing the rubber from becoming stuck to the ceramic. Generally spark plugs are in located in areas of high temperature, and the grease is formulated to withstand the temperature range expected.
Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector.
Last edited by BlindSpot; 03-27-2018 at 07:07 AM.
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03-27-2018, 08:33 AM
#40
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