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Uneven acceleration

9K views 47 replies 11 participants last post by  mikl613 
#1 ·
I don't know if it's supposed to be like this, but I notice after the transmission shifts into second and mostly third, there's a dead spot in acceleration for about half a second, then there's a small surge. It kinda makes the driving experience not terribly pleasant.
 
#4 ·
I get this too. Like a flat spot. I was thinking it was the traction control or stabilitiy control, holding back on the throttle. I turned off both (long press the TC button) and it seemed like it may have stopped it as far as I cound tell. Could you all try this and post your result or have you already ruled this out?
 
#8 ·
Or your one of the unfortunate souls, like me, that has running issues that are impossible to diagnose. Keep your fingers crossed.

You can get a cheap Bluetooth obdII scanner to keep an eye on the boost. You may find that the boost is building as it should but you're just going nowhere for reasons that are unexplained
 
#9 ·
Hey, folks. I've already got over 12K on my 2020 GT N-Line (100+ miles per day). Here's what I've found...

Replaced OEM plugs and coil-overs with MSD coils and Bosch double iridium plugs. They really helped, but...

The tranny shifts into higher gears at or about 2.5K RPM, whether in Sport or normal mode. That means that just about the time the turbo spools up (c. 2K RPM) the stupid tranny shifts and you're back at 1.5K RPM, below the turbo actuation. Lags, spits, misfires.

So, the answer is leave it in manual mode and use the flappy paddles to shift at or above 3.5K RPM, the way God intended. That'll solve most of your problems.

Hope this helps.

-zed
 
#10 ·
I've tried this too, and the coils helped just a bit. I have been looking into the possibility that maybe I'm getting too much boost. I think reading the OBDii scans may be misleading without an analog boost gauge, which I'm thinking about installing...

HOWEVER, I decided to try closing down my plug gaps. I believe stock is .028. The lowest I've seen recommended is .025. I decided to see how it would act at .022. I gotta tell ya, it's been the only thing with a noticeable difference that I can actually quantify.
Watching the scanner, I notice that my fuel trims are always very high, especially when idling. Since I closed down the gaps, I've noticed my fuel trims drop significantly while idling, idling smoother, and on the highway, instead of being around +4 or +6, I'm actually hanging around 0 or even going negative. My fuel efficiency has increased as well where I usually get 31-33 on the highway I'm getting 35-37. ( I drive 250 miles a day sometimes)

Not sure if anyone else is gonna try this, but I'm gonna go lower this weekend because while it's significantly better, it's still not perfect.
 
#11 ·
Takeeon:

Not sure about the safety of narrower plug gaps. It is an aluminum block, after all... But, you may not be totally wrong either. After I pulled the OEM coil packs and NGK plugs, I saw evidence of arcing above the stem, a neat little burn just above where the plug meets the cylinder head on CYL #3.

For those with less inclination to mess with manufacturer's specs, at least try my driving setup, which yields nearly flawless results (I said 'nearly'):

1. Sport mode off, since you'll be shifting at whatever RPM you choose. Manual shifting in Sport mode has given undesirable results (misfires), for me.

2. ESC/TC on (cuz I gotta have cruise control and there's none with it turned off).

3. Shiftronic on (stick pulled to the left) and use either the shift lever to up- or down-shift (1st to 2nd gears on corners only, for me), or the flappy paddles (my preferred methodology).

4. And finally, never shift below 3.5K RPM, so you can stay in the turbo's power band! Personally, I never shift below 4K and frequently ~5K. I never redline the engine, cuz I want it to last awhile, y'know?

NOTE: Basically, what you're doing is 'dumbing down' the car by removing some crucial decisions the ECM and TCM are horribly, laughably mismanaging. If I weren't concerned about voiding my warranty (but I certainly am), I'd probably consider an actual custom tune (but, I'm not gonna cuzza the aforementioned) to make the danged thing work the way it oughtta.

As a final note: If you're in a low-leverage situation (e.g., residential driving, wide-open highways, etc.), the car's performance is perfectly acceptable in Sport mode (all it does is keep the revs up a little higher... kinda pointless, really, unless higher rev-sound equates to 'sporty' to you) and full-auto DCT mode... But, if you have to rapidly accelerate even moderately (1.5K cruise with sudden increase to 3.5 or 4K), you can expect a single- or multi-cylinder misfire and undriveable power loss that won't correct until you pull over, turn off the engine, open the door to discharge electrics and then restart like nothing ever happened. It's waaay stupid, and not in the good sense of the expression.

P.S.
My Fiesta ST was a banshee, but they don't sell 'em in the Americas anymore (all trucks and SUVs, gag/puke), so I got the GT N-Line with tech pkg as the nearest suitable replacement. It's a comfortable car, all the bells and whistles... but, it ain't comparable to the FiST for performance, by a long shot.

-zed
 
#12 ·
My symptoms slowly crept back in, but they're still not at bad as they were. After adjusting I reset the ECU. It runs pretty good for a few days until it finally gets around to testing the evap system, then things slowly creep back in.

When it's running well, there's not any need to to even get to 3.5k most of the time. The low end torque is excellent.

All that aside, my fuel trims are still looking good and this fuel economy is blowing my mind
 
#13 ·
Takeeon:

My daddy always used to say, "If you drive like an old lady, you'll end up with an old lady's' car."

Now, granted, the low-end torque's alright... until you put your foot down, even a little. Then -- on my specific vehicle, at least -- the engine sputters, misfires and becomes virtually undriveable until I limp over to the shoulder and do a complete 'cold reboot', as outlined in my previous post.

For anyone who'll consider my findings:

1. Less drivetrain computerization is required, not more. There's a seat-of-the-pants sport car in this thing and imma find it, even if it hairlips the Governor!

I'm about 95% there, right now; I just can't trash 'muscle cars' the way I used to in my 2,400 lb. FiST, cuz Inertia is a Universal Law and responsiveness/'suddenness' is all about weight-to-power ratio. I doubt we'll see any Ed Block or Pros vs Joes videos featuring a GT N-Line.
(NB: I also doubt I'll ever be able to approach the FiST's performance in the GT, without significant and costly engineering-level mods. The HGTN-L just weighs too much at 3,500 lbs. -- see, 'Universal Law', above -- with the same HP and torque as the FiST, but no factory-standard 30-sec turbo overboost to 230 HP/210 ft-lb; but it's fast enough to do all the things I need it to do, given the right driver. Meaning, me.)

2. I'm not saying you should drive the car aggressively at all times. Rather, that it should driven as aggressively as is prudent for longevity in the vehicle, whenever you get the chance -- like, when entering a highway or making a passing/overtaking maneuver.

My goal when driving is to get to my cruising speed (speed limit plus 10%, e.g., 77 in a 70) as rapidly as possible and then make as few adjustments to speed as practicable thereafter. It keeps the car running right... or, as right as possible given the apparent computer problems this manufacturer has throughout their lineup. Why pay for and drive a titular sport car, if all you really need is a squirrel-in-a-cage, 86 hp/56 ft-lb FWT putter-buggy?

3. On my 108-mile roundtrip daily commute, I always accelerate up to </= 6K RPMs (sub-7K-redline), but fewer than 7 occurrences, for 30 seconds or less each time, in my total 2 hour drive (i,e., between 2 and 3 total minutes of 'hard acceleration' over a 2-hour timeframe). The rest of the roundtrip, I'm chillin' in cruise, Normal mode and full-auto DCT, letting the computer do most of the highway cornering, pulling about 2.5K RPM and making 35-37 MPG, depending primarily on headwind/tailwind factor. And I'm doing that on mid-grade 91 octane.

ADVICE: Dumb the car down, as described in previous post. ...It's already too smart for its own good...

Parenthetically
-zed
 
#14 ·
Upon further review:
Turning off Electronic Skid Control
does virtually eliminate uneven acceleration. So now, I only turn it on when at cruising speed on the highway and in low-leverage situations, as described above, so I can use cruise control. Kind of a PitA, given that my Fiesta ST would do cruise control regardless the status of ESC.

...and why in the name of all that's holy would the ESC be so stingy? I could see it if the GT N-L had the HP/torque of a Veloster N or i30 N. 'Granny' overkill and no Hyundai-based solutions likely forthcoming for this discontinued model. Meh.
 
#15 ·
Agreed, after reading this thread earlier, I started turning it off and it makes a big difference.

I own a 2018 Porsche Cayman GTS and I bought the N Line for my daily driver. Naturally I compared the Elantra to the Cayman and the Elantra paled in comparison. With our area getting cooler temps with approaching winter I pumped up the tires 3 psi over the recommended pressure and wasn’t I pleasantly surprised at how much better it handled. Less darty, more planted and more confidence inspiring in high speed cornering. Still no Porsche, but a great improvement.
 
#17 ·
If anyone is still reading this:

I swear by Gumout products. I used them regularly with my Fiesta ST (FiST, to enthusiasts of the car, sadly discontinued in the Americas), about once every month and a half, or so.

I don't really know why it took me so long to use a bottle with my 2020 Elantra GT N-Line; but, I stuck in one of their complete fuel system treatments for GDI vehicles ($4.77 at Walmart) about 3 weeks ago, on an empty tank before fill-up and... Whoosh!

In Sport mode -- even in the plain-Jane, usually hiccup-y DCT -- the danged thing took off like its butt was on fire! And it's still running hell bent for leather,1.5K miles later.

Looking like my idea of a sport car, after all, wasting all those big-bore lead sleds when challenged... This is getting good!

-zed
 
#21 ·
Product page:
Regane® Complete Fuel System Cleaner – Gumout

gumout.com

Walmart sells it online for $4.44 USD:
https://www.walmart.com/ip/Gumout-Regane-Complete-Fuel-System-Cleaner-6oz-510014W/16888904
NOTE: The treatment packaging I use has GDI prominently displayed on the label; but the detail on Walmart's page says:

"CLEANS
GDI/direct and port/indirect fuel injectors, intake valves and ports, piston tops, cylinder heads, combustion chamber

CONDITIONS
Fuel to fight ethanol and water corrosion

PREVENTS
Future carbon buildup.

BEST FOR
Maximized performance and fuel economy in one fill-up, reduced emissions

DIRECTIONS
Oxygen sensor safe. Safe for use in turbocharged and supercharged vehicles. Will not void OEM/manufacturer’s warranty. Add entire bottle to nearly empty gasoline tank, then fill tank with up to 21 gallons of gasoline. For best results, do not refill tank until near empty. Use every 3,000 miles." (Emphases mine)

-zed
P.S.
I am not affiliated with, nor a paid promoter of Gumout. Their stuff just works.
 
#22 ·
Thanks for the info. I have a manual and find that it acts up as others have mentioned. I try to remember to shut off the traction control and the stability control off. I try to run 93 octane when ever I can. Top Tier of course. I have heard that using a different weight oil in Hondas 1.5 turbo, 0-18 or 0-16, I dont recall at the moment, has stopped the oil/gas dilution problem that Honda has with the 1.5 turbo. I had one in 2017 and you could smell the gas on the dip stick. So I will try that next oil change. I think I will try re-gaping the plugs just a little. Winter tires are going on next week as it is getting a lot colder here in Michigan. LOL Very disapointed with Hyundai for not continuing the hatchback GT N Line. I really like the car. Has more to offer than the Civic si. And now has more power over the 2022 si
 
#24 ·
This goes back quite a few years but I think it’s relevant. In the early 80’s I was a property manager for Shell Oil co and they released their new premium gas at the time SU2000 and I fell for the hyperbole about how great it was and began using it in my 1984 Nissan Sentra. I learned quite a bit about gas, octane and gas additives back then. My Sentra started to lose performance about a year into using the SU2000 and it turned out that Shell was using a dye in the fuel that contributed to deposits, that plus using premium higher octane in an engine that didn’t require it also contributed to deposits.

I ended up using Harley Davidson combustion chamber cleaner in the car followed up with Multiple applications of Gumout Regane. Yes, Regane existed way back then. The two measures returned the cars performance back to new and I started using the Regane at every oil change. I had that car for over 12 years and 150,000 miles and the performance never suffered or declined after again. I sold the car to a coworker and he got another three years use trouble free until he dumped it because of bad body rust.

Regane is good stuff and that and not using fuel that has higher octane than required is what I do with my current vehicles.
 
#25 ·
I tried the gumout. Still running through 1st tank that had the gumout added, but it really does seem smoother, down to about 1/2 tank right now. Only have 10,000 miles, catch can and breather bypass since about 4000, so I have been protecting the intake tract most of its life. However not much top tier gas around me, and the manual does say to treat the gas at every oil change if not available. Perhaps the injectors, fuel line, etc. are getting cleared up from the low grade fuel.
 
#26 ·
Will_p:

GDIs are known to carbon up. Also, they don't much like ethanol, which is pretty much ubiquitous in gasolines today. Gumout Complete Fuel System treatment purports to address both those issues. I'm not a petrochemist. I just know it works, it ain't snake oil; but, I wouldn't use it beyond the manufacturer's recommendation: once every 3,000 miles. As to breaking down your cylinder heads or over-gapping your plugs -- as others are doing -- I just wouldn't. I'm pretty sure that would void my warranty and possibly ruin my engine. I've swapped out the OEM plugs and coil packs; but, I'm not otherwise gonna alter the car mechanically, for the same reason.

I can say that Gumout has made a significant improvement in my 2020 GT N-line and that I will use it religiously henceforth, as I did with my previous 2 Fiesta STs.

Happy motoring!

-zed
P.S.
I'm 63 years old and my daddy taught me to drive at the age of 8 in his sky blue Ford Falcon station wagon (3-speed satellite-shift manual, 'three on the tree') on an abandoned section of The Old Galveston Highway. When I was 13, I taught my mom how to drive... So, I've been around the block a couple times.
 
#27 ·
Your P.S. Made me smile. My father had a 63 Dodge Dart with the three on the tree and he decided to teach me to drive it. He was aghast that I knew how to drive it when we started. What he failed to realize and that I never told him, was that I had been working on an old Divco Milk truck with a guy as a runner For about a year. The old man that I worked with was an alcoholic and he had some customers on the route that he would personally take the order in and leave me in the truck with the engine running. These special stops would entail him being gone for 10-15 minutes and he’d return reeking of alcohol. While he’d be in these special stops, I had learned to drive that old Divco by driving it forward a few hundred feet and then backing it up to where I started. This gradually progressed into driving around the block as I got braver with time.
My ability to drive the truck came in handy more than a few times while working for him when he got so drunk on a few occasions that I had to drive the truck back to his home.
P.S. This was back in the early 60’s when I was 11 or 12 years old. I made five dollars a day every Saturday doing this for a couple of years. The days were long, we’d leave at dawn and it was not uncommon to go 12 hours or more to complete his route.
 
#28 ·
I see what you're getting at, but I don't understand why it's a problem that can't be solved and we should all be interested in a proper solution. There seems to be varying levels of the same issue going around here, mine being particularly terrible. Turning off traction control helps a little mashing it from a stoplight, but when I trying to get from 60 to 70 on the highway, it doesn't do anything.

If anyone around here has a scanner of any sort, my guess is you'd look at the fuel trims and see they're super high. My combined fuel trims are usually 20% or higher at idle. So high there should be a code, but there never is. The car runs too rich. I can smell the sulfur all the time. It's either the factory time is F'ed or a sensor is lying throwing off the air/fuel mixture. The fact that it runs almost normal after you reset the computer points this out, so unless there's a massive air leak, which I've tested for many times, the trims should stay real close to zero in most conditions. And while some times, mashing the gas makes it move, there's a lot of times when it just falls flat on its face.
I've been driving vehicles with forced induction for 25 years and never ran into issues until GDI became a thing. (My 2017 Cruze also had issues where it would go into limp mode after driving for a day or two)
 
#29 ·
Try one of these:

I got one before I figured out the car needed new plugs, coil-overs and Gumout (e.g., not the turbo's fault) and the tuner box really didn't do much with the car still in stock condition. Those easy upgrades improved the car so much I forgot to put it back on for a while. It's a 5-minute install, so I thought, why not try it again?

I did and now I'm completely fixed. Just absolutely trashing turboed lead sleds, trucks, SUVs... everything but motorcycles. Very sudden, hiccup free acceleration to over 100 MPH...

Closest I got to busting a knuckle was swapping out trash NGKs for Bosch iridiums. Closest I got to reprogramming my ECM was resetting code-trips with my phone via BT to OBDII. So simple, a girl could do it.

My car is now everything I hoped it might be when I bought it 4 mo/16K miles ago. Sometimes, less work is the more effective solution.

-zed
 
#31 ·
I got one before I figured out the car needed new plugs, coil-overs and Gumout (e.g., not the turbo's fault) and the tuner box really didn't do much with the car still in stock condition. Those easy upgrades improved the car so much I forgot to put it back on for a while. It's a 5-minute install, so I thought, why not try it again?
So if I'm reading this correctly, installing Bosch Iridium spark plugs, new coils, and using Gumout should have it running great without the need for the tuning box? The tuning box just makes it as fast as we all wish it could be?

What coils did you go with?
 
#30 ·
To those who might be interested in TDI's box, some notes:

  1. It ships from Chelmsford, England, UK (The World, The Solar System, The Universe). I got it within a week, shipped free via DHL.
  2. Follow instructions carefully. For the GT-NL, it's only two bypass connectors. You will want to remove your filter box to reach one of the connectors (10mm socket x 4 bolts).
  3. 50 mile burn-in (or 1 leg of trip to work for me). After that, it has 'learned' your ECM/turbo data and gains set in. If you get impatient and start switching program modes before that, you're only going to disappoint yourself. Show a little restraint and you will be rewarded.
  4. Reverse the install before taking it for service (another 5 minutes) to avoid stink-eye, at the minimum. After service, when you get back home, let the engine cool down and reinstall tuner box.
  5. It's so simple to do, I don't even have to read the little instruction sheet anymore, after having installed and de-installed twice for dealership service.

Just remember to swap plugs and boots for premium grade ones and run at least 1 bottle of Gumout ($1.44 at Walmart), or you won't really see much alleviation of hiccupping throttle and limp-mode.

With all that done properly, the little car even roars a bit now, so you can shift by pitch rather than eyeballing the tach. ...Just the way I like it!

I've said my piece and I'm out.
-zed
 
#39 ·
...No, it's when a plug (or other part) degrades the vehicle's designed performance that it becomes cheap and worthless. That's what this thread is about: sub-standard performance from a superiorly designed automotive platform...

...And it's because of cheap-ass, sub-standard plugs and coil packs. Quick search on i30n OEM standard plugs reveals "NGK 97080 SILZKR8E8G Laser Iridium Spark Plug" heat range 8, as I listed above. The only time they go cooler is on remap.

You may be over-thinking this.
 
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