My car went in for service today for the lump in my seat, milky polished wheels, and the ruff idle.

My car has a jerk about every second. Sometimes it happens every 1/2 second. It feels like a lump.

They ran the diagnostics and found nothing wrong with the car. They even sat in two others and said they felt the same as my car. I will sit in them tomorrow to verify for myself.

Here is the question. Most of you say that your C6's are VERY smooth idlers. How can two other cars at the dealer have the same ruff idle as mine but plenty of you state that your cars are Lexus smooth at idle?

I am thinking most of you haven’t owned a Lexus

Maybe you just don't care or don't pay attention. I wish I could sit in a C6 that is completely smooth.

I know my car runs strong from the 12.7 in the 1/4. So I don't think it is a injector. Besides, wouldn’t that show on the diagnostic?

I just hate sitting at lights with the whole car shaking. No comments like “It has 400hp live with it” or “it’s the cams” If it were the cams than why don’t all of them do it?

AMG cars and other 400+ hp cars idle smooth as glass. Why can’t Chevy do it? Why can’t my dealer fix it? This sucks.

 

My C6 idles smooth in comparision to the ZO6, not quite as smooth as the C5 but close. Maybe you are used to overhead cam motors. This is a pushrod motor and the more cam you put the more it effects smoothness of idle. I would have the dealer ride with the candy bar as they call it, plugged in under the dash and check for loose ground. I personally have no desire to own a Lexus, I want some character and soul to my engine and did I mention TORQE.

 

umm, you bought a Vette, not a queer AMG or *** Crap. You got a Chevy V8. You dont know the meaning of choppy unless you own an LS1 F-body. The C6 is the Smoothest running Vette I have ever been in. You should ride in a '66 427, that idle will put the fear of the almighty into you.

 

In response to the original post, I can't recall anyone stating the idle was anywhere near as smooth as a Lexus. I just sold my GS400, and the C6 is nowhere near as smooth. I wouldn't call it "rough", but it is what it is given the design of the motor.

 

FLC6, most of the threads I have read, guys have been talking about their C6s idling Lexus quiet...not smooth. Mine is very quiet (almost "is it on?") at idle. It also rocks and bumps at idle, (every few seconds)just a little, but enough to let you know the car is awake and there are 400 ponies under the hood. As far as your other 2 problems, yeah, take it in. As for the idle feel and roughness, I think you are okay. And I personally like it.

 

Whyyyyyyyyyy!!!! Why are people comparing a 400hp Ameriacn V8 to a Japanese 6 or 8 cylinder? They are cam-ed differently and are made with two different goals in mind. Sports car vs Luxury car. People do your research before you buy.

 

Maybe when you install your Corsa exhaust from WCC it will go away.

 

Let's see, 4.0/4.3 DOHC VVTi in the lexus is a performance engine (in fact, it puts out more HP/torque per liter than the LS2), so I fail to see why you have an issue with people comparing things like NHV with other the cars. Do you think the 3.8L in the 997 idles like the LS2? Unlikely.

 

Thank you for proving my point about how they are cam-ed differently.

 

Comparing a DOHC motor to a 2 valve per cylinder pushrod motor is not an apples to apples comparison. In certain areas (Europe) motors are taxed on displacement. So they must use costly measures (in terms of weight and $$) to achieve HP. Therfore, they use expensive, bulky DOHC motors to do the same thing that can be done with a larger displacement engine with smaller physical dimensions at a lower cost and superior fuel economy. The HP/Liter unit of measure is not applicable here where there are no artificial influences such as taxation based on displacement. HP per $$ is more valid measure here and the DOHC motor can not match the LSx in those terms. Where the lowest cost, lowest weight takes the advantage, the LSx motor will shine.
Let's look at the basic equation for HP.

HP = TQ x RPM/5252.

The 4 valve motor (when taxed on displacement) has less displacement. And since torque is largely a function of pressure times area acting on the piston, the smaller motor will have less torque. But the 4 valves per cylinder allow it to achieve a higher RPM before running out of breath. So looking at the equation, it has less TQ, but more RPM, for the same result (HP). The larger engine makes more TQ but runs out of breath sooner since it only has 1 intake valve vs. the DOHC motor's 2 intake valves. In addition, in motors such as the LS2, they have increased the cam duration so that it doesn't run out of breath quite as soon. That increased cam timing is what gives the "rough" idle. The increased low end TQ of the larger 2V motor is very pleasing to the soul and responsible for the tire smoking, neck snapping characteristics of an LS2 vs a smaller displacement DOHC motor that has to wind up to produce HP. A rough idle due to a "big cam" is not the same as a rough idle due to a missfire. If the idle of the LS2 bothers you, I would suggest the XLR. To quote a wise man, research before you buy.

 

Thanks need-for-speed. I love all cars but I look at each one for what the manufactorer is trying to do. And you can't make a VW a Porcshe.

 

I didn't say the lumpy idle bothers me.

I didn't know it was normal. Now that I know I'm ok with it. Geeez, you love to put first Corvette owners down don't you. We all have to start somewhere.

 

I think you need to return to the classroom.

You surely aren't serious whne you call DOHC engines bulky and expensive?

Please tell me you're not.

 

I hope you don't think I'm putting you down. You have a very fine car (C6) and I hope it gives you many miles of smiles. I understand about being new to such things.

 

I hope you don't think I'm putting you down. You have a very fine car (C6) and I hope it gives you many miles of smiles. I understand about being new to such things. Welcome to Corvette heaven.

 

Porsches aren't really known for a smooth idle... I'm around a lot of them and most don't sound as calm as my cammed LT4.

 

Wow. I just don't know what to say? I mean your response is so articulate and well structured.

 

There's a difference between "lumpy" and rough.
Never been in a C6, but the C5 Z06 has a very slight and very nice factory lope at idle. You're probably feeling the same thing in the C6 since it has the same cam as a 2001 Z06.

If you don't feel this in other cars, it's because they either have overhead cams, or a transverse mounted engine (in which case any "lumpiness" would not translate into a rocking motion).

My 6 cylinder ranger pickup even has a slightly lumpy idle (it's the 4.0L pushrod engine).

 

From your first post it sounds like it's more of a hiccup, which definitely wouldn't be normal... the fact you say it only happens once a second or two makes me think it could be something more. I think you should sit in another C6 and see if it's the same. My car has a "lump" in the idle because of the cam, but I wouldn't call it rough... just constant and mellow. Don't give up yet.

 

Yes, I guess that is why, at the pinnacle of factory competition at the F1 & world superbike levels, we see so many 2-valve pushrod motors.