Recently looked at a 2014 Corvette to purchase. The car has low mileage and is in beautiful condition, however, it has a misfire. Noticeable enough that when sitting in the car at idle, you can feel the shimmy. Opened the hood and you can see the engine is moving. Strikes me odd that an ignition issue would occur at 20k miles. Any thoughts?

 

You know that they don't idle smooth right .
what makes you say it's missing? Do you have a misfire counter on it or you think it's missing because of a rought idle ?

Dave

 

C7s have a little bit of chop at idle. Definitely not smooth.

If there's a misfire, in general there should also be a check engine light and a stored code.

C7s will on occasion have a plug wire pop off a coils or a plug. A quick and easy check is to verify the wires are all seated....even if they appear to be seated. You can reach all 8 coil packs and you can reach the driver's side plugs. The passenger side spark plugs take a bit more work due to the fuse box being in the way.

More likely you're just feeling what's normal.

 

Ok - my terminology. So maybe not a misfire but just a rough idle?

 

I have looked at 2 other 2014s (was late to the party on those), but those engines at idle were rock solid.

 

Have a pre-purchase inspection performed by an experienced mechanic.

 

If you don’t have a scan tool to read misfires take a dollar bill and hold it up to the exhaust…if it gets “sucked in” while running you have a misfire !!

 

If you have a miss fire at all, you would have a engine light. A vacuum leak will cause a rough idle'

 

My '14 Stingray runs great. But whenever you pull to an extended stop, such as into your driveway or waiting in line at a stoplight, the rpm will drop to the 'idle speed' and after just a few seconds the engine will be much 'rougher'. I chalk that up to the way these things run. No CEL, plug boot on securely, etc.

 

Not always !!…ECM has to see a certain number of misfires to illuminate the MIL…also if the car is running on fumes the misfire monitors are disabled…first thing I look at when diagnosing a misfire is the fuel quantity.

 

There's quite a bit of information being shared here, some of which I don't necessarily agree with. I just bought a '16 Stingray, and experienced something that sounds similar to what you're describing. The first thing I noticed about the car was somewhat of a rough idle. Did a bit of research, and found most people said the same thing they're saying on here, "the C7's chop a little". That put my mind at easy a little, but then I started noticing a bit of a hitch when driving at highway speeds. While maintaining speed, cruise control on, the car would kind of hiccup ever so slightly. If you weren't paying attention you'd think it was just a minor bump in the road, except it wasn't. I could see the RPM drop just barely! I eventually did get a CEL after some spirited driving, P0300 which is just a random misfire code. I took it back to the dealer and they did a "tune up" which they just replaced the plugs and wires and called it good. I tried re-creating the issue that caused the CEL, and not CEL, so thought all was good. Fast forward a couple weeks, I took the car to the shop to get full exhaust/tune, and while I had it there, because my gut was telling me something was still wrong, I had them throw in a cam package. Come to find out, there was a broken valve spring. It must not have been very bad because it didn't do any damage, and wasn't throwing the CEL, at least, in the brief time I drove it around and went WOT a couple times.

Long story short, for everyone saying the "chop" is normal. I don't necessarily agree with them. I had an '18 Camaro SS 1LE (same engine), and it did not chop at all. Now that I have a cam, I can't confirm or deny how much the C7 "should" chop, but know that my rough idle, was not normal. You could always try to find someone local that has one just to compare to. Of course, now my rough idle is normal because of the cam Additionally, if you do have a misfire, it is not an automatic CEL. I can't tell you the criteria the computer is looking for, but occasional misses aren't going to throw a code. If you have a fouled spark plug, you'll probably get a CEL, but if it's something more subtle causing the miss, it may need certain criteria to throw the CEL. Just my .02 based on what I recently experienced.

 

Dude if you were driving with a broken valve spring , that motor was doing alot more than idling rough 🤣

 

Yep perfectly normal , with the lift and duration of the stock cam it will not idle like your father's Buick 😅
Dave

 

I am telling you, it wasn't. It wasn't even throwing a code when I brought it to them. I guess it could have broken during the initial dyno pull, but that's not what he said. When I called to check status, he said everything was going well except it had a broken valve spring and that it was good that I decided to do the cam package. I did not hear clicking when I had it, and it wasn't idling super rough either. I am far from an expert, but I am also not completely ignorant to performance cars. I found it hard to believe as well, but maybe it depends on where the break was? Maybe if the break is further up or down the spring makes a difference?

 

I am sure it happened on the pull , your dash would have lit up like a Christmas tree .... , as me how I know .....

Dave

 

My 2014 has a slightly rough idle, but so did each of my three C5s.