‘22 GT2 acceleration judders

[Royalstorm]

New car jitters:

I have a new 2022 Stinger GT2 with ~700 miles.

When driving last night I noticed that when cruising around 45-50mph in sport mode at around 2000 rpm, when I accelerate moderately, the boost kicks in and acceleration is also a bit juddery. If the car downshifts, acceleration seems pretty uniform but if it remains in a lower gear, it’s not smooth. Is this engine lugging? I never experienced this in my 2018 GT. No matter how I accelerated, boost and acceleration were uniform and smooth. I’m going to have my dealership look at it next week to get their opinion but curious if anyone else has experienced similar inconsistent acceleration.

 

[MerlintheMad]

I already addressed this with a theory: bad plug(s) (and the boot/coil, if bad, will ruin replacement plugs). I thought "lugging" too, that's because I drive almost entirely in manual gate using the paddle shifters. But experimenting with auto transmission still produced the "lugging" (hesitation) feeling. Over the course of six months I finally solved the issue, for now, heh.

 

[Royalstorm]

I already addressed this with a theory: bad plug(s) (and the boot/coil, if bad, will ruin replacement plugs). I thought "lugging" too, that's because I drive almost entirely in manual gate using the paddle shifters. But experimenting with auto transmission still produced the "lugging" (hesitation) feeling. Over the course of six months I finally solved the issue, for now, heh.

Yeah, thanks for the information. When you say hesitation, did you experience a repetitive shutter or just consistent smooth (albeit slow) acceleration?

 

[MerlintheMad]

Yeah, thanks for the information. When you say hesitation, did you experience a repetitive shutter or just consistent smooth (albeit slow) acceleration?

I called it "stutter" mainly, but shudder or judder also describe a consistent feeling of a cylinder misfiring under boost. I would get a CEL and it would go out quickly unless I had just done a WOT acceleration or something close to WOT, then the CEL would stay on indefinitely: this was when the sparkplug was cracked, as I later found out. Even at the worst, if I just drove the car instead of the turbos, you would never know that anything was amiss.

 

[Royalstorm]

I called it "stutter" mainly, but shudder or judder also describe a consistent feeling of a cylinder misfiring under boost. I would get a CEL and it would go out quickly unless I had just done a WOT acceleration or something close to WOT, then the CEL would stay on indefinitely: this was when the sparkplug was cracked, as I later found out. Even at the worst, if I just drove the car instead of the turbos, you would never know that anything was amiss.

Interesting. I haven’t had a CEL which I did during my brief stint with my GT1 that did have a cracked plug. The stutter I am experiencing may just be true engine lugging though it seems like the car should automatically shift if it’s experiencing excessive load a higher gear, right? But it seems like it just tries to power through it at the higher gear…

 

[MerlintheMad]

But it seems like it just tries to power through it at the higher gear…

More gas. My "stutter" would disappear under boost in a couple of seconds: which made me think that the engine was lugging too. This went on for most of 4K miles, then I got an oil change and they discovered the cracked plug. About two weeks later, the "stutter" was back and I started to get CELs: and in the end, the stutter would not go away under boost: so, there is a degradation of performance that occurs over time: that, and no two sparkplug failures behave exactly alike, so I must suppose.

 

[bfglitch]

Personally I can't imagine a car with 700 miles on it with bad coils and/or plugs already...but...you never know. I'd say bring it to Kia (if you have any with techs that know what they're doing), and have them deal with it under warranty.

 

[Royalstorm]

Personally I can't imagine a car with 700 miles on it with bad coils and/or plugs already...but...you never know. I'd say bring it to Kia (if you have any with techs that know what they're doing), and have them deal with it under warranty.

I agree. Seems unlikely and not behaving like the lurching I experienced with a cracked plug on my other GT1 that I had briefly. I’m just trying to understand if a less pronounced jutter is normal when car is under boost at a higher gear or if this is something problematic.

 

[bfglitch]

I agree. Seems unlikely and not behaving like the lurching I experienced with a cracked plug on my other GT1 that I had briefly. I’m just trying to understand if a less pronounced jutter is normal when car is under boost at a higher gear or if this is something problematic.

With my 22 GT1, I haven't noticed any strange judder type acceleration while in a higher gear, on boost, prior to downshift. Then again usually when I'm cruising around in a higher gear I don't have the boost gauge on. When cruising I'm usually checking out my mpg. Next time I'm doing some highway type driving I'll put on the boost gauge and try accelerating enough to kick in boost but stay in gear.

Does this happen in any mode or is it in specific modes (eco, comfort, sport, etc)?

Try to grab the speed, gear, mode, etc you're in as you're accelerating while you experience this, prior to it downshifting and smoothing out. I'll see if I can replicate.

 

[StingertimeNC]

I think it is the engine lugging. Mine always does this on slight inclines typically in comfort mode. it just seems reluctant to downshift unless you really get into the pedal. I drive 90% of the time in sport mode, unless I'm going long distance on the highway and I want to smooth out the suspension. Sport mode seems to keep it out of the tallest gear and it's more willing to downshift under lighter throttle. If it lugs at all I'll just grab the paddle and drop it a gear or two. I also think it's unlikely the plugs or coils are bad this quickly.

 

[Royalstorm]

With my 22 GT1, I haven't noticed any strange judder type acceleration while in a higher gear, on boost, prior to downshift. Then again usually when I'm cruising around in a higher gear I don't have the boost gauge on. When cruising I'm usually checking out my mpg. Next time I'm doing some highway type driving I'll put on the boost gauge and try accelerating enough to kick in boost but stay in gear.

Does this happen in any mode or is it in specific modes (eco, comfort, sport, etc)?

Try to grab the speed, gear, mode, etc you're in as you're accelerating while you experience this, prior to it downshifting and smoothing out. I'll see if I can replicate.

I appreciate your thoughts. I can definitely do that. When I initially noticed it, I was in sport mode going 45-50 mph. I was in automatic so not sure what gear I was in. If I punched it, car would downshift appropriately and power and acceleration seemed smooth. It was during a slight incline when I gave just enough extra throttle that the boost kicked in to probably 10 psi and rpms rather slowly climbed from 2000 to 2200 or so, and I felt this rhythmic pulse-like sensation with pretty subtle but present rapid ebb-flow in acceleration for 1-3 seconds. I’ll try to replicate again in the next day and maybe record events on my phone.

 

[Royalstorm]

I think it is the engine lugging. Mine always does this on slight inclines typically in comfort mode. it just seems reluctant to downshift unless you really get into the pedal. I drive 90% of the time in sport mode, unless I'm going long distance on the highway and I want to smooth out the suspension. Sport mode seems to keep it out of the tallest gear and it's more willing to downshift under lighter throttle. If it lugs at all I'll just grab the paddle and drop it a gear or two. I also think it's unlikely the plugs or coils are bad this quickly.

Good to know. I agree that comfort mode would make sense but just seems a bit odd in sport mode to have it struggle at 2000 rpm. And again, I remember sometimes pushing my 2018 GT and occasionally it wouldn’t downshift but managed to at least maintain consistent smooth acceleration. It almost fell like my old wrx that I drove that I think had a boost leak and wouldn’t accelerate consistently though that was typically under higher load/rpms and with maximum boost.

 

[socalvn]

give it a chance to break in and you're also getting used to a new style vehicle

 

[Royalstorm]

With my 22 GT1, I haven't noticed any strange judder type acceleration while in a higher gear, on boost, prior to downshift. Then again usually when I'm cruising around in a higher gear I don't have the boost gauge on. When cruising I'm usually checking out my mpg. Next time I'm doing some highway type driving I'll put on the boost gauge and try accelerating enough to kick in boost but stay in gear.

Does this happen in any mode or is it in specific modes (eco, comfort, sport, etc)?

Try to grab the speed, gear, mode, etc you're in as you're accelerating while you experience this, prior to it downshifting and smoothing out. I'll see if I can replicate.

I was able to replicate again this evening, this time on highway going probably 60 mph with rpms around 1900. Pushed just enough to kick in boost but stay in gear and could feel the car with ever so slight lugging back and forth (rapid oscillator feeling, not a harsh bucking like a bad coil) even as rpms climbed pretty quickly to 2500. So it seems to occur at multiple speeds when engine is at 1900-2000 and boost kicks in. It’s a little disconcerting given no recollection of this behavior in my previous ‘18 GT (3.3L base).

 

[bfglitch]

I was able to replicate again this evening, this time on highway going probably 60 mph with rpms around 1900. Pushed just enough to kick in boost but stay in gear and could feel the car with ever so slight lugging back and forth (rapid oscillator feeling, not a harsh bucking like a bad coil) even as rpms climbed pretty quickly to 2500. So it seems to occur at multiple speeds when engine is at 1900-2000 and boost kicks in. It’s a little disconcerting given no recollection of this behavior in my previous ‘18 GT (3.3L base).

Hmmm interesting. I'll try to replicate while driving around a little later, but from what you're describing I don't think I've ever experienced it.

 

[Royalstorm]

Hmmm interesting. I'll try to replicate while driving around a little later, but from what you're describing I don't think I've ever experienced it.

Appreciate it. I’d say it’s fairly subtle but just enough inconsistency to tell there is something not running quite right (at least compared to my ‘18). I suppose the tuning very likely was different in my ‘18 and sport mode ran rpms higher in all gears, so engine lugging wasn’t as prevalent?

 

[bfglitch]

Appreciate it. I’d say it’s fairly subtle but just enough inconsistency to tell there is something not running quite right (at least compared to my ‘18). I suppose the tuning very likely was different in my ‘18 and sport mode ran rpms higher in all gears, so engine lugging wasn’t as prevalent?

I took a pretty quick drive. Probably not quite enough but tried a few things to replicate it. I think maybe once I might have felt what you're talking about but I'm not entirely sure if it was me accidentally modulating the throttle a bit. Once I was around 50mph or so and around 2k rpm I flipped the car into "manual" and gave it a bit of gas until I noticed it building boost. Only once did I feel like the car was sort of "undulating" faster and slower but I'm not 100% positive it was me inducing it. I've noticed that sometimes at that stage the slightest change in pedal pressure is noticeable. When trying to replicate it a few times after that and trying to focus on keeping the pedal in one exact spot while accelerating without downshifting, it felt pretty smooth. I'll have to try it though when I have a little more open road. Almost impossible around here since everyone has to take up every single lane even if they're all doing the exact same speed, so usually when I have an opening I gun it. Makes it tough to test this out

 

[FarmerMagnum]

Mine definitely acts the same at low rpms <2500 under heavy load. I've only owned the 22 so I can't compare to earlier year models, but I always considered it normal as the car does not behave badly anywhere else or under heavy acceleration.

 

[Royalstorm]

I took a pretty quick drive. Probably not quite enough but tried a few things to replicate it. I think maybe once I might have felt what you're talking about but I'm not entirely sure if it was me accidentally modulating the throttle a bit. Once I was around 50mph or so and around 2k rpm I flipped the car into "manual" and gave it a bit of gas until I noticed it building boost. Only once did I feel like the car was sort of "undulating" faster and slower but I'm not 100% positive it was me inducing it. I've noticed that sometimes at that stage the slightest change in pedal pressure is noticeable. When trying to replicate it a few times after that and trying to focus on keeping the pedal in one exact spot while accelerating without downshifting, it felt pretty smooth. I'll have to try it though when I have a little more open road. Almost impossible around here since everyone has to take up every single lane even if they're all doing the exact same speed, so usually when I have an opening I gun it. Makes it tough to test this out

Thanks for trying to replicate. I’ll keep testing different driving speeds too. I actually have kept it in automatic and then five enough throttle to spool up the turbo but not induce a downshift, and that’s when’s it’s most noticeable.

 

[Royalstorm]

Mine definitely acts the same at low rpms <2500 under heavy load. I've only owned the 22 so I can't compare to earlier year models, but I always considered it normal as the car does not behave badly anywhere else or under heavy acceleration.

Interesting. Thanks for your feedback.