2011 5 sp. bucks intermittently at low RPM on light ~ moderate throttle - Hyundai Forum - Hyundai Enthusiast Forums

Go Back  Hyundai Forum - Hyundai Enthusiast Forums > Vehicle Line Up > Hyundai Accent
Reload this Page >

2011 5 sp. bucks intermittently at low RPM on light ~ moderate throttle

Hyundai Accent Offered in a 2 or 3 door hatchback, or 4 door sedan ,this compact offers room to seat 4 people and excellent economy.

2011 5 sp. bucks intermittently at low RPM on light ~ moderate throttle

  #1  
Old 01-09-2019, 09:54 PM
Junior Member
Thread Starter
Join Date: Jan 2019
Posts: 3
Default 2011 5 sp. bucks intermittently at low RPM on light ~ moderate throttle

I bought the car used with 21K mi. on the clock from CarMax. History unknown, except it came from NJ, and was very clean. Obviously well cared for. No particular history in online VIN searches. Currently at 35K mi.
Prior to purchase I had it evaluated by a local Hyundai dealer. They found no problems other than old firmware, which they updated. Motor & running gear is box-stock AFIK.

It's run fine until recently.

Code history:
~31K mi. P0302 - examined and swapped coils #1 & #2. Code never returned.
~33K mi. P0303 - close examination of #3 coil showed a very faint hairline crack on the outer surface at the plug end. Not a die line. An actual crooked crack. Not sure it even went all the way through. Replaced that coil with a new Delphi coil. Code never returned.
~33K mi. - replaced plugs along with the #3 coil above. The old plugs looked fine, just normal spark erosion.
No other codes have been seen during my ownership.

Let's define some parameters:
Buck - the feeling that spark or fuel is cut for a fraction of a second, then resumes. If you've ever experienced a single-coil vehicle that is way overdue new plugs, under load (climbing a hill), where the spark is simply "blowing out", that's what it kind of reminds me of.
Intermittently - doesn't always do it, although the longer it runs, the more likely it is to buck. When it bucks, it usually only bucks once.
Low RPM = 1,500 ~ 2,000 RPM.
Low ~ moderate throttle = that which would be applied in, say, second gear after making a right turn at an intersection, accelerating to a 2-3 upshift in a 25 MPH zone.
Or,
Coasting toward a red light. Light turns green. Downshift 4-3 @ 30 MPH (~1,700 RPM in 3rd.) and accelerating in a 35 MPH zone.
It'll buck in any gear; it seems RPM-dependent.

Cold starts and the first 5 ~ 10 miles or so miles it runs fine regardless of throttle or load.. The longer it runs, the more likely it is to exhibit the "bucking" symptom at low RPM. By the time it's run for 20 ~ 25 mi. it tends to buck more & harder under the same throttle and load.

Fully warm and just off idle after 20 ~ 25 mi. there is a noticeable stumble just off-idle when applying throttle from a standing start. Again, low RPM at low ~ moderate throttle.

EDIT: After running long enough to exhibit the problem, there is a very random, subtle, instantaneous stumble at idle. It's not a cyclical miss; happens maybe once every 5 ~ 10 seconds. It's barely felt, and deflects the tach needle by only the tiniest amount, maybe the width of the needle tip if that.

Higher RPM (2,500 and up) and greater throttle up to WFO loads do not exhibit any bucking or performance problems.

The fact that it begins to misbehave only after running for a time leads me to believe it may be heat related. I just don't want to throw parts at it hoping something will stick.

What say the forum motorheads?

Thanks for your help.

slmjim
 

Last edited by slmjim; 01-11-2019 at 07:10 AM. Reason: Clarity & additional symptom info
  #2  
Old 01-10-2019, 12:00 AM
Senior Member
Join Date: Aug 2015
Location: Iowa
Posts: 138
Default

That's a GDI engine? - Check for crud on the intake valves.
 
  #3  
Old 01-11-2019, 07:18 AM
Junior Member
Thread Starter
Join Date: Jan 2019
Posts: 3
Default

Originally Posted by allegretto View Post
That's a GDI engine? - Check for crud on the intake valves.
I haven't looked close enough to know if it's port, GDI or CRDI. The online research I've done is inconclusive.

What would the mechanism be that would cause the symptoms described if intake valve deposits are present?

Also, see the edit re: idle symptom.


slmjim
 
  #4  
Old 01-11-2019, 11:42 AM
Senior Member
Join Date: Aug 2015
Location: Iowa
Posts: 138
Default

The deposits accumulate on the back of the intake valve and on the walls of the intake channel. They are restricting the airflow. That causes rough idling , hesitation , misfires, increased fuel consumption. In sequential port fuel injection engines the valves and the intake channels get cleaned by the fuel and this problem does not occur.
Meanwhile there are cleaners available that do a reasonable job of removing the deposits. I don't have experience with them because I don't have a GDI engine. CRC products tend to be trustworthy.
This guy gives you a good idea of what to expect:

Good luck.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Shay Moshe Itshacovich
Hyundai Accent
0
11-08-2015 10:42 AM
Neil
General Tech Help
3
01-01-2013 10:00 PM
tiBuronGt
PRIVATE For Sale / Trade Classifieds
0
01-03-2009 11:31 PM
outtowinpahc
PRIVATE For Sale / Trade Classifieds
4
02-09-2008 12:06 PM
mpryjd2
Hyundai Sonata
2
02-27-2007 05:00 PM


Thread Tools
Search this Thread
Quick Reply: 2011 5 sp. bucks intermittently at low RPM on light ~ moderate throttle


Advertising
Featured Sponsors
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.