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Second C5 question--rough idle


C5 Nik

My car is a stock 2000-6 speed and it think that it idles very rough (when I am stopped at a light I notice it the most).

My last car was a 90 w/ 150k miles and I expected a rough idle because it was old. Should I expect a rough idle or have that taken care of while I still have a warranty???? Any suggestions????

Hi there,
Well, it depends, may I ask what your mileage is ???
You see, your L98, had a substantially different camshaft profile over the LS1 that you have now.
You may see a little roughness, as this is due to the rapid opening and closing of the valves. It is very technical, however, it is called ramp speed, where the valves move up at a high rate of speed, to obtain better flow.
If you are over 10k on the clock, I would add a bottle of GM part number 12345515 to your fuel tank the next time you fill her up. This fuel system cleaner is only to be used every six months, and is extremely concentrated. Sometimes, at the shop, when we have a rough idle, the use of this cleaner will assist in the cleaning of the injectors.
This is a simple starting point to the diagnosis. Please let us know how you make out, because if you are not getting a 'service engine soon' light on your DIC, then you are not misfiring enough to create problems.
Please keep us posted, and welcome to the CAC, c4c5:hb
Hey : Your car should not idle rough , even being a six speed you should not any idling problems at all .
Things to check :
1- Check spark plugs or just replace
2- O2 censor could be dirty , pull and clean
3- New Air Filter
4- Check MAF censor plug , loose or dirty connection .
5-Have your coil paks check out . One could be going bad .
Thanks ,
ROUGH idle

Nikki- the previous guys gave you some good advise. But you may also try what some refer to as an idle relearn. All you have to do is disconnect the battery for 5-10 minutes. Reconnect the battery & let the car idle another 5- 10 minutes. Its cheap an easy & sometimes cures the problem. If you plan to do any intake mods in the future, you will need to do this procedure. I have also seen a dirty MAF wire cause this problem. Hope this helps- good luck.
Thanks for the tips. I took the car to the dealer and they said there was nothing wrong. I will try your tips and let you know if anything comes from them.

What type of driving is the car subjected to? If you are in much stop and go traffic you might be building up deposits on plugs, injectors, or the O2 sensor. Try driving on an open stretch of highway for about 15 minutes or so where you can get the RPM up to or above 2000 for a while. This should burn off deposits on plugs, injectors and O2 sensors. If it smooths out, it didn't cost more than a couple gallons of gas, and you will probably enjoy the ride.
If it doesn't smooth out, keep knocking on the Goodwrench door until they find the cause, and fix it. I don't think the 2000 LS1 engine had enough cam to cause a shake at idle.
I have a 2002 Z06, and that cam does cause a slight shake at idle, but it's an obvious cam shake, not from some other cause.
Did you just recently get gas before this happened? Since the dealer couldn't pull up any codes it has to be something minor. Has the air filter been checked?

Because of the profile and firing order of the Ls1 it will have a little "lump" in your idle. but you'll know it if something isn't right.

Back to the gas, could have gotten some trash or water in it. When your down to about a 1/4 tank run some F.I. cleaner and take it on the highway to burn all the crap out/ and or some smoking burns outs somewhere :).

Hope this helps.

Wow, I can't suggest anything else for you. Everyone pretty much made all of the suggestions. Pick one, better yet pick them all and try them. I am sure they will work for you, one might be better than the next so you will need to experiment. Good luck.
Ok My .02

1) Pull the codes you can do it from the dash

(have to read book to post instructions)

2) Change air filter

3) Plugs...they are easy to do...

Drive it..and let us know how it is after.


We have already installed a new air filter (I was really impressed how much easier it was to remove/install compared to the 90).

The car only has 28K on the odometer--I find it hard to believe that the plugs would be bad so soon.

The dealership said it did not have any codes. We are going to take it to another dealer that has a "corvette expert" (he is also an old family friend so his opinion is trusted). We shall see what happens then.

I will keep everyone posted. I am going to try the fuel inj cleaner like C4C5 recommended. I only drive 1 mile to work, so it takes a awhile to go through a tank of gas. :)

Yeah it's not alot of miles

You pull the plugs.it tells a story.

You don't know what the prior owner put in the tank

It will tell you how each hole is burning.

It will make you check that all the plug wires are ok.

It will tell you if any are loose!

And if they are ok, clean em, check gaps and put em back in.

Have you tried the gas thing yet? I might be something a simple as that since the problem is not throwing any codes.

Good Luck.
You might have already answered your own question with today's post. You only drive one mile to work. That's hardly enough time to come off the start sequence. Do you drive it much on weekends? I think your thoughts on having your friend check it out might help, because you trust his opinion. Chances are he might tell you the same thing but there is always something more credible about somebody you know and trust.
I still think you don't drive it enough to get the O2 sensors cleaned, and maybe the EGR valve is also sticking from deposits.
Of course keep in mind that we are all trying to trouble shoot this car over the internet, not exactly the best way to do that.
Good luck.


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