Rossi6998

I am a prior owner of a 2009 Coup with an automatic transmission. I traded the 2009 in for a 2014 Coup with an automatic transmission. I have had the car since late April and notice it is not very smooth when I am holding a steady speed of about 40 miles per hour, then accelerate slightly. The key word is slight acceleration, such as when driving in traffic. I might be letting off the gas prior to the acceleration, but don't quite remember.

I can't figure out if the car is searching for the right gear, if the car is switching from V4 to V8 mode, or if it is just a different feel from the LS3 to the LT1 engine.

I'm calling it a "hiccup" because I don't want to label it a "hesitation" or "jerk" since it does not seem that severe.

I seem to notice it more with the air conditioning on, and that may be causing a strain on the car which makes this hiccup more noticeable.

Right now, I don't believe there is anything wrong with the car and it is the feel of the new engine design, but I am curious if this is happening to others and their thoughts.

Thanks

C7cmnthru

Can't say for sure but mine does the same thing. I think it's the AFM (not sure if we have a locking torque converter) . 2 suggestions. First, drive in full manual mode in sport setting to see if it does it. It won't go into V4 in full manual mode. Second, in full auto mode, bring up the AFM indicator light in the DIC. See if it changes when you feel the hiccup. If it does, that might be your answer.

I haven't researched it, but you might want to do a forum search on torque tube vibrations.

Would suggest a quick trip to your local service dept if after this you remain concerned.

bob guzzy

You could be feeling the AC cycling on and off, it will be more notiecable at speed in higher gears when you put a strain on the drivetrain.

Rossi6998

I will have to play with it a little more. This car definitely has different noises and vibrations compared to the C6. I obviously expected this since the engine and design of car are completely different. Just trying to see what others are experiencing.

I did run a search regarding this issue, unfortunately, everything came up but the issue I was interested in.

Thanks for the input so far.

kp

You can display if its V4 or V8 on the dash, its on one of the info screens.

These do have lockup converters and of course for mpg reasons they upshift pretty quick at low throttle and giving it a little more gas it will have to switch to V8 mode, unlock the converter if its locked and downshift - of course you are going to feel something.

While some say the AFM is completely seamless its not, at the right throttle and speed its pretty obvious but you have to pay attention to notice. I would turn on the display and see if what you are feeling is the car switching from V4 to V8.

buckeye4

owc6

I'd be really surprised if this is going into V4 at 40 mph, no matter what else is going on.

Cruiter

Actually it can and does. My subdivision is off a rural route about a mile long where the speed limit is 35 and a couple of county deputies live right in the middle of that stretch (shame cause it's a nice curvy road with only a few homes). So it's smart to stick to the speed limit. At 35 and steady it will always go to V4 even in sport mode. I have the A6 and of course sometimes override it by using the manual shift mode.

kp

+1

I live in a very hilly area and at 35-50mph its amazing how long the V4 holds on even with some throttle. Its on quite a bit and just cruising out of my subdivision at 20mh it will go into V4 as well. It doesnt really bother me but it spends quite a bit of time in V4 with an auto.

Rossi6998

Played around with the manual mode today and did not get the "hiccup." Put it back into sport mode and got the "hiccup." SO, it is either the AFM system or the way the gearing is set up...

Thanks to all.

ezra1973

Finally someone who has the same problem as me. I actually have my car at the chevy dealer right now for this same issue. I got it to make the hick up noise with the chevy guy in my car. They told me they think it's a bad muffler. The noise sounds like its coming from the middle rear of the car. It does have a rattling noise to it. So hopefully that's it. I will keep you posted once I get the car back.

Jim Barker

I'm waiting on a fix from GM before I let the dealer mess with it. There are issues with hanging in V4 too long in E mode. This is when you get garbled exhaust and then some vibration in whole car! 30 to 40 MPH light pedal driving with varied road conditions. Still think V4 should be tuned out of Sport and Track modes completely!

Rossi6998

I agree... The AFM should only be active in the Eco and Tour modes. I wish GM would push an update for this to occur.