Misfire or rough idle on the 2012 GMC Terrain
When misfire or rough idle gets reported
Owners of the 2012 GMC Terrain report misfire or rough idle at a median of 40,000 miles. A quarter of the reports come in before 20,000 miles and a quarter after 95,000 miles, from 13 reports that carried an odometer reading.
A part like this is normally expected to survive 92,000 miles. It is the 8th most-reported problem on this model year.
The mileage distribution
The reported range runs from 20,000 miles at the tenth percentile to 100,000 miles at the ninetieth, a spread of 82,816 miles across the middle 80% of reports.
When the reports scatter this far, the mileage is telling you about how these cars were driven more than about the part itself.
38% of the dated reports were filed under 36,000 miles.
The whole distribution
| 10th | 25th | Median | 75th | 90th |
|---|---|---|---|---|
| 17,956 miles | 17,956 miles | 41,000 miles | 95,860 miles | 100,772 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 5 model years of this car. It shows up earliest on the 2019, at a median of 5,000 miles, and latest on the 2010 at 100,000 miles.
By volume the 2011 carries the most reports, with 14; the 2012 has 14. 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.
The vehicle has been in the shop for 10 to 12 times due to failure with the engine misfiring as well as traction control lights and stability trac as well as transmission not shifting right and loss of power while driving on major highways and brought into the dealership where they tell me they can find or make the problem reappear. But have shown the dealership service department video and have had 3 general motor techs that they hired from hp and been told the vehicle is safe and that there will be no more problems but have been in the vehicle while the problems have happened and have it on video to the point where I almost lost my life yesterday night. The vehicle is a death trap and many customers including myself on gmc terrain forum as well as online have had the same problem and have been told the same thing that it is nothing to worry about but it is. Please help have been told by gm to keep my mouth shut they would offer me 5,000 dollars for my troubles and that my kids are worth that much from a legal advisor at general motors legal. Have ask to be taking out of the vehicle for something safe and still I'm being told…
The vehicle has been in the shop for 10 to 12 times due to failure with the engine misfiring as well as traction control lights and stability trac as well as transmission not shifting right and loss of power while driving on major highways and brought into the dealership where they tell me they can find or make the problem reappear. But have shown the dealership service department video and have had 3 general motor techs that they hired from hp and been told the vehicle is safe and that there will be no more problems but have been in the vehicle while the problems have happened and have it on video to the point where I almost lost my life yesterday night. The vehicle is a death trap and many customers including myself on gmc terrain forum as well as online have had the same problem and have been told the same thing that it is nothing to worry about but it is. Please help have been told by gm to keep my mouth shut they would offer me 5,000 dollars for my troubles and that my kids are worth that much from a legal advisor at general motors legal. Have ask to be taking out of the vehicle for something safe and still I'm being told…
The vehicle has been in the shop for 10 to 12 times due to failure with the engine misfiring as well as traction control lights and stability trac as well as transmission not shifting right and loss of power while driving on major highways and brought into the dealership where they tell me they can find or make the problem reappear. But have shown the dealership service department video and have had 3 general motor techs that they hired from hp and been told the vehicle is safe and that there will be no more problems but have been in the vehicle while the problems have happened and have it on video to the point where I almost lost my life yesterday night. The vehicle is a death trap and many customers including myself on gmc terrain forum as well as online have had the same problem and have been told the same thing that it is nothing to worry about but it is. Please help have been told by gm to keep my mouth shut they would offer me 5,000 dollars for my troubles and that my kids are worth that much from a legal advisor at general motors legal. Have ask to be taking out of the vehicle for something safe and still I'm being told…
Also reported on the 2012 GMC Terrain
Excessive oil consumption
Other engine problem
Timing chain, belt or tensioner failure
Wiper or washer failure
Other visibility problem
Other electrical problem
How far this goes
Complaints are voluntary, so 14 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 2012 GMC Terrain?
Across 13 owner reports that included an odometer reading, half were filed by 40,000 miles. A quarter were filed before 20,000 miles and a quarter after 95,000 miles. 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 2012 GMC Terrain?
14 reports have been filed with NHTSA, about 0.2 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