rviscuso

2017 Stingray 2LT M7. When slowing down or coming to a stop as engine RPM's approach 1200 the engine jumps about 100 rpm. Gear selection makes no difference; 1st 2nd etc. Clutch is engaged. This is very consistent. Also, when slowing down from high rpm's, lets say about 4000 -6000, as the rpm's start to come down maybe 500-1000 there is a slight momentary surge (just like the 1200 rpm problem but this one is at high rpm) then the rpm's continue to drop until I hit the accelerator. What do you guys think? Is this typical/normal? This is my first Corvette so I am not sure what to expect.

Larry/car

I had a 2014 M7 and traded it on a 2017 M7 both surged while decelerating to a stop. Not sure about those high RPMs, seldom get to 5,000. I think it is the emission system doing its thing.

rviscuso

Larry, thanks for the reply. I don't like what the engine is doing; a minor annoyance. None of my other vehicles do this (carbureted and injected) but if this is the way it was designed.... well, then that's just the way it is. I'm wondering if the A8 is the same?

rviscuso

Anyone else experience this engine surge?

dataporter

I have a 2014 M7 and I can't say I've experienced this. It's not Active Rev Match? You said the clutch was engaged, so I guess not.

rviscuso

Yeah, clutch is engaged. I usually drive with ARM off, but even on it still surges.

WelderGuy

Does the car surge forward when the RPMs go up? You'd definitely have to feel that.

rviscuso

Yes, most definitely it can be felt. That's what brought it to my attention in the first place. Not only is it consistently noticeable at 1200 rpm, it is also noticeable when coming down from high rpm's, ie: run it up to 5000, let off of the pedal and as it drops to lets say 4,500 there is a slight bump upwards before rpm's continue to drop further. This too can be felt.

AORoads

You said the word, "consistently" in your last post above. Is this consistent? Can you do it consecutively every time you decel and it hits an rpm bump up at around 1200 rpm? I can't say it's normal, (and dealers sometimes say things are normal that aren't) but I'd suggest a trip to a dealer might be in order.

You don't state where you live and if you're using a/c now. A long time ago, I had an econobox with a/c and a manual trans. It did something pretty alarming esp. when pulling up to a light: the a/c compressor would cycle on, and the rpms would jump by at least a hundred or more to compensate for load on engine. Enough to keep this driver on his toes so that I didn't jump the intersection. Same thing on curving on-ramps. It was always with a/c on though---don't recall it in winter or when a/c was off.

Speednet

My 2016 Z06 does this, and my previous 2014 Stingray did it also. I don't like it because I like to gear-brake as much as possible, and this sort of ruins the last part of it. However it's not a dangerous thing as it is very consistent and does not "surge" the car as much as it seems to let up on the gear braking.

WelderGuy

Maybe the ECU is programmed to reduce the fuel flow to zero during deceleration, and then start delivering some fuel again around 1200 RPMs to keep the engine from stalling when you disengage the clutch. I can't think of any reason you'd get a similar surge at higher RPMs, though.

I also recall some cars I've had that surged when the AC compressor engaged, but that's been a long time ago on cars with much smaller engines, as mentioned above.

Something like that would be very annoying.

rviscuso

Well, it's starting to look like a normal operation since a few of you have indicated the same engine behavior. But, just because a few cars have the same behavior does not mean it is normal.

A/C is off.

I live near Sacramento CA (home of the heatwave). I brought it to the dealer and they said it was normal. However.... when I got home I read the service writer's description and it was not exactly how I described the situation. He stated to inspect for rpm drop - that when driving at slow speeds reving vehicle to 1200 rpms customer states rpm's go up 100 then begins to drop normally when letting off gas. Hmmm, I do not recall saying that I was the one reving the engine to 1200. Somehow it got lost in translation. The car had four additional miles on it so I'll assume that the tech drove it. There were other issues so this wasn't the only thing he would be looking for.

cyberay

It's programmed that way to reduce NO2 emissions.

Red08

It must be something with the C7. Neither my 2008 C6 with A6, or my 2016 Silverado does this.

mschuyler

I'm on a road trip and it did it to me today several ties. 1st time I thought it was me, but next time I ow damn well I didn't do it. Clutch in, coming off the freeway where I had been doing 70, engine surge. I think it is dangerous. What is going on?

Patches

My '14 M7 does it.

rviscuso

I think I should have done a better job with my homework before posting. I did a little more searching and found:

https://www.corvetteforum.com/forums...ow-speeds.html

Sounds like the same thing I experience. However, disengage the clutch and rpm's drop smoothly. That may be the technique to avoid the surge.

Abnormal normal = annoyance.

AORoads

If you're in the Sacramento area, maybe ask/trip to Rio Vista and Abel Chev. Rich Willhoff there will know if it's normal.
http://www.abelgm.com/Corvette-Specialists

wgood

Is the rev matching on or off ????? Wayne

rviscuso

I have read plenty of good recommendations about Abel's. About an hour and a half drive. I may make the drive as a day trip.

In the meantime I sent an email to the dealer (in response to a survey) just to see if they can give a better explanation than 'normal operation no repairs needed'.

Rev match makes no difference. In case I did not say before, this only happens with clutch engaged, in gear. If disengaged, there is no surge at 1200. Now that I am thinking.... I never tried in neutral with clutch engaged. Homework for me.

I think I need to figure out how to quote... one of these days.