Misfire or rough idle on the 2018 Kia Forte
Only 4 reports for this mode came with an odometer reading, which is too few for percentiles to mean anything. The page is here because someone linked to it; treat the figures as anecdotes, and see the full report for this year instead.
When misfire or rough idle gets reported
There are 6 reports of misfire or rough idle on the 2018 Kia Forte, 4 with a mileage attached. That is too few to place the failure on the odometer with any confidence.
A part like this is normally expected to survive 92,000 miles. It is the 5th most-reported problem on this model year.
The whole distribution
| 10th | 25th | Median | 75th | 90th |
|---|---|---|---|---|
| — | — | 37,100 miles | — | — |
Read the 10th percentile as “one report in ten arrived this early”. Exact figures are shown in this table because it is the table of record; everywhere else on the site they are rounded to the precision the sample can carry.
What a percentile can and cannot tell you here
These five numbers describe the readings owners gave, in order. The median is the middle one: half the reports arrived below it. The 10th and 90th are the edges of the bulk of the distribution, and the distance between them is the part worth reading. A tight spread — say 70,000 to 95,000 miles — points at something that wears out on a schedule, and the schedule is knowable. A wide one, 20,000 to 190,000, points at a fault that hits some cars and never troubles others, which means the mileage on the listing in front of you tells you very little about your odds.
What these figures are not is a survival curve. Every reading here comes from a car whose owner filed a complaint, so the sample contains only failures: it cannot say what share of the fleet made it past 150,000 miles untouched, because those owners had nothing to report. Nor is the mileage the moment of failure — it is the odometer reading as recalled at the time of filing, which may be weeks later and is sometimes rounded to the nearest ten thousand by the person typing it.
Percentiles are shown at all only once 8 readings exist for the vehicle and mode. Below that the middle of a handful of numbers is noise wearing a decimal point, so the figures are withheld rather than dressed up.
What happens, and what it costs
Putting it right typically runs $250–$1,600 at an independent US shop. That range is an editorial estimate held in this site's failure-mode catalogue, not a figure from NHTSA, and it is a repair cost rather than a diagnosis cost.
The same failure on other years
The same failure is reported on 3 model years of this car. It shows up earliest on the 2018, at a median of 35,000 miles, and latest on the 2017 at 185,000 miles.
By volume the 2017 carries the most reports, with 17; the 2018 has 6. A mode that appears across most years of a model is usually a design choice rather than a bad batch.
If one year stands out to the left, that is the year to avoid; if the whole line sits at a similar mileage, this is wear rather than a defect in one production run.
Tick median reported mileage Solid middle half of reports Faint 10th to 90th percentile Colour how bad the failure is when it happens
What owners wrote
Verbatim from NHTSA complaint narratives, trimmed for length. The mileage is the one the owner gave.
Well at present my car only has about 400 miles on it I only picked it up on 4/4/2018 & it's starting to sound like the 2016 ford fiesta I traded in.. When stopped at a light the idle gets rough and if this was the 1960's I would say it had a bad spark plug or carburetor issues; however, this is 2018 so not sure but it's the only thing I can relate the idle issue with.. I spoke with the salesperson at the dealership that sold me the car but he said he knows nothing about inner workings of cars so I made an appointment with the service department for 4/25/2018 since I cannot get there at the times they want me to; and until then I can only monitor it.. This issue started after I had the car approximately one week; nothing like florida car dealers selecting a car for me off their lot that has issues..
This is a follow-up to my original complaint # 11088519 on 4/10/18.. When I brought the vehicle to the dealer on 4/25/18, I was told it was a bad spark plug huh on a new car; what would be next.. In any event the dealer had to order the spark plug another huh on that too.. Spark plug is in & I have an appointment tomorrow 5/2/18 to replace & repair & none too soon because the car sounds & runs 'terrible'.. Sitting at a light it sounds worse than the 2016 fiesta I traded in terrible rough idle & really bad when accelerating from a light which could be dangerous.. This kia forte at present has 465 miles on the odometer..
Also reported on the 2018 Kia Forte
Other engine problem
Other electrical problem
Other powertrain problem
Other speed control problem
Instrument cluster or gauge failure
Other fuel system problem
How far this goes
This page is kept out of search results because 6 reports is not enough to publish percentiles from. It stays reachable because somebody looking at this exact car would rather see the reports than be told there are none.
Complaints are voluntary, so 6 is a floor and not a count of affected cars. Mileages are typed in by owners and cluster on round numbers. And the mode itself is assigned by software reading the complaint text, which is reliable in bulk and fallible one report at a time.
Questions this page answers
At what mileage does misfire or rough idle happen on the 2018 Kia Forte?
Across 4 owner reports that included an odometer reading, half were filed by 35,000 miles. A quarter were filed before — and a quarter after —. These are the mileages owners reported when they complained, not a prediction for any individual car.
How common is misfire or rough idle on the 2018 Kia Forte?
6 reports have been filed with NHTSA, about 0.1 per 1,000 vehicles. Complaints are voluntary, so this is a floor rather than a count of affected cars.
What this is and is not. These are the mileages at which owners chose to complain to a federal agency, which is not the same as the mileage at which the part fails on every car. It skews toward failures that happened outside warranty, cost real money, or frightened someone. It is still the only public dataset that carries failure mileage at all, and the shape of a few hundred readings is informative even when a single one is not. Methodology · JSON · this failure on other cars
Source Owner complaints and recall records published by the US National Highway Traffic Safety Administration, model years 1996–2027 Figures rebuilt Published by AtWhatMileage How every figure is computed