PulsCar analysis of NHTSA public data, September 2026 Topic: jerking, bucking, shuddering and hesitation during acceleration License: CC BY 4.0 (attribution: "PulsCar analysis of NHTSA public data, September 2026") SOURCES - NHTSA Office of Defects Investigation flat file COMPLAINTS (FLAT_CMPL), field dictionary https://static.nhtsa.gov/odi/ffdd/cmpl/CMPL.txt 777,040 owner complaints received 1 January 2015 - 8 September 2026. - NHTSA ODI flat file MANUFACTURER COMMUNICATIONS (FLAT_TSBS), field dictionary https://static.nhtsa.gov/odi/ffdd/tsbs/TSBS.txt 187,827 distinct communications (NHTSA_ID) over the same period. - Downloaded and indexed 17 September 2026; queries run 18 September 2026. QUERY - "a jerk while accelerating" Step 1. Full-text search of complaint narratives for: jerk/jerks/jerking/jerked, buck/bucks/bucking, surge/surges/surging, shudder(s)(ing), lurch(es)(ing), stumble(s)(ing), hesitate/hesitates/hesitation, sputter(s)(ing), stutter(s)(ing). -> 33,850 complaints. Step 2. Negation filter: at least one symptom word must NOT be preceded within 40 characters by no / not / never / without / n't / any. Step 3. Acceleration context: an acceleration phrase (accelerat*, gas pedal, throttle, from a stop, take off, going uphill, merging, passing, "step on the gas") within 400 characters of the symptom word. -> 13,262. Step 4. Exclusions: motorcycle-only makes and motorcycle model codes; narratives matching pedal-misapplication and "death wobble" phrases. -> 12,255. Step 5. Sentence-level test: the symptom word and either an acceleration phrase or a powertrain word (transmission, engine, gear, shift, RPM, clutch, torque converter, CVT, misfire, spark plug, coil, fuel) must appear in the SAME sentence, and that sentence must not be about steering, glass, roof, frame, rust, airbags, seat belts, ABS, windshield, headlights, paint or door latches. -> 10,601 complaints. This is the published set. SAMPLE READING (required before publishing any keyword count) 30 random matches were read at step 4: five described something other than a powertrain jerk (a detached glass roof, a steering failure, frame rust, an ABS fault, a self-applying brake), about 17%. After step 5, 30 fresh random matches were read: 26 described jerking, bucking, shuddering or hesitation during acceleration; 4 did not (two unintended- acceleration crash narratives, one steering failure, one no-start). Observed false-positive rate for the published set: about 13% in a sample of 30. Counts in the article are described as "complaints whose narrative describes a jerk, buck, shudder or hesitation in an acceleration context", never as a count of confirmed defects. FIGURES QUOTED IN THE ARTICLE (published set, n = 10,601) Towed 3.22%, crash 2.18%, fire 0.26%; 92 complaints report at least one injury. Mileage: median 50,000, quartiles 15,000 and 89,042 (n = 6,092 with a usable odometer reading; rows with miles <= 0 or >= 400,000 dropped). 40.7% of those readings are at or below 36,000 miles. Shop could not duplicate the fault, or called it normal/as-designed: 527 (5.0%), counted by phrases such as "could not duplicate", "unable to reproduce", "no problem found", "operating as designed", "within specification". Ford Focus 1,272 and Ford Fiesta 246 complaints (14.3% of the set together), median 39,450 miles, 48.1% at or below 36,000 miles, concentrated in model years 2012-2017. NHTSA component tags: power train 6,552; engine 3,281; vehicle speed control 1,510; fuel/propulsion 1,382. A complaint can carry more than one tag. WHAT OWNERS SAID WAS REPAIRED (file: jerk-what-owners-said-was-repaired.csv) Text captured after "diagnosed with/as", "determined that", "found that", "replaced the", "replacing the", "needed a new", "needed to be replaced", "repaired the", "dealer replaced" and matched against part keywords. 1,264 of the 10,601 complaints contain such a phrase; that is the denominator. Categories overlap, so shares do not sum to 100. IMPORTANT: this is NOT a frequency ranking of the causes of jerking. It is a ranking of what gets written into a federal safety complaint, and cheap fixes (a coil, a plug set, a cleaned throttle body) are massively under-reported because owners do not file federal complaints about them. The article says so in the text next to the table. BULLETINS (file: jerk-shudder-bulletins-by-make.csv) Communication summaries searched for shudder/judder/jerk/surge/hesitation/ bucking/stumble: 1,893 distinct communications. Of those, 888 tie the symptom to acceleration, shifting, launch or the torque converter - the published set. 429 of the 888 mention software, reprogramming, calibration or a flash; 128 mention transmission fluid. Summaries are NHTSA's published abstracts, not the full bulletin text, so both shares are floors rather than exact measurements. LIMITATIONS - Complaints are unverified owner reports, not failure rates, and are not normalized by vehicles on the road. High-volume models produce high counts. - Nothing here ranks manufacturers by reliability and no such ranking can be derived from these counts. - A model with a well-publicized transmission problem attracts complaints from owners who read about it, which inflates its count relative to quieter faults. - Mileage is owner-entered and often rounded to the nearest 5,000 or 10,000. ------------------------------------------------------------------------------ CASE SENSITIVITY — SECTION ADDED 19 SEPTEMBER 2026 ------------------------------------------------------------------------------ NHTSA stores complaint narratives in ALL CAPS for records filed through roughly 2020 and in mixed case for records filed from 2021 on. A case-SENSITIVE search of the narrative field loses about 92% of the complaints filed after 2020, so this is the single largest way an analysis of this database can go wrong while still looking finished. Every query behind this file is case-insensitive. SQLite's LIKE and its FTS5 full-text index both ignore case by default, and no query in this work uses GLOB or any case-sensitive comparison. This was not taken on trust. On 19 September 2026 every published folder was re-checked against the same database, comparing the figures here with what a case-sensitive query would have returned. The result: the complaint set published here (33,850) is LARGER than the absolute ceiling a case-sensitive search of the same terms could have returned (9,064 narratives). A case-sensitive query cannot produce a bigger set than itself, so the bug is ruled out for this folder by arithmetic, not by assurance.