PULSCAR ANALYSIS — P0304 (CYLINDER 4 MISFIRE) IN NHTSA'S PUBLIC FILES PulsCar analysis of NHTSA public data, September 2026. License: CC BY 4.0. Attribution: "PulsCar analysis of NHTSA public data, September 2026." Published alongside https://www.pulscar.io/blog/p0304-code ------------------------------------------------------------------------------ 1. SOURCE FILES ------------------------------------------------------------------------------ NHTSA's published flat files, downloaded 24 September 2026 and loaded into SQLite without modification: COMPLAINTS_RECEIVED_2015-2019, _2020-2024, _2025-2026: 780,071 distinct vehicle complaints by ODI number, received 1 Jan 2015 - 21 Sep 2026 FLAT_RCL_POST_2010 (recalls reported from 2010) TSBS_RECEIVED_2015-2019, _2020-2024, _2025-2026 (manufacturer communications) Bulletin PDFs were located through api.nhtsa.gov/safetyIssues/byNhtsaId and downloaded from static.nhtsa.gov on 25 September 2026. The 23 documents marked "Y" in p0304-recalls-extensions-bulletins.csv were read in full; the other two rows (GM recall 25V-274 and a Honda service article) were read in NHTSA's published text. ------------------------------------------------------------------------------ 2. THE COMPLAINT SET (p0304-345-complaints-flags.csv) ------------------------------------------------------------------------------ Case-insensitive whole-word match in the narrative on \bP[O0]304\b (P0304, also written PO304 with a letter O). Result: 345 complaints. name no other cylinder code and not P0300 184 contain a code range such as "P0301-P0304" 61 (pattern) Flags (pattern, case-insensitive): coolant or antifreeze 120 (34.8%) spark plug 97 engine, short block or long block replaced 82 ignition coil 60 fuel injector 45 valve, lifter, rocker or camshaft 36 piston rings 21 recall, extension, extended warranty or settlement 125 flashing or blinking light 51 word "stall" 48 NHTSA flags: towed 4, crash 1, fire 1, injured 2, deaths 0. Mileage: 91 rows with 0 < miles < 400,000; median 87,701; quartiles 60,000 and 126,979. Filed by year: 2015 5, 2016 3, 2017 7, 2018 12, 2019 11, 2020 24, 2021 20, 2022 16, 2023 38, 2024 58, 2025 72, 2026 (to 21 Sep) 79. By manufacturer group: Ford and Lincoln 127 (coolant 108, engine or block replaced 62, piston rings 0); Honda and Acura 95 (coolant 3, injectors 28, piston rings 15, spark plugs 38, recall/extension/settlement 46). ------------------------------------------------------------------------------ 2b. WHICH CYLINDER EACH MODEL NAMES (cylinder-code-fingerprint-by-model.csv) ------------------------------------------------------------------------------ All complaints naming any of P0301-P0308 (whole word, O or 0): 1,346. Because owners paste bulletin ranges, the comparison uses only the 1,027 complaints that name exactly one cylinder code and not P0300: P0301 191, P0302 305, P0303 259, P0304 184, P0305 42, P0306 29, P0307 10, P0308 7. The CSV gives, for every model with five or more complaints, both the "names" counts (any mention) and the "lone" counts (single-cylinder only). The article uses the lone counts. Examples: Honda Odyssey 32 lone, all on cylinders 1-4; Honda Pilot 30 lone, 26 on 1-4; Chevrolet Silverado 1500 21 lone, 8 on cylinder 4; Jeep Wrangler 19 lone, 9 on cylinder 2 and 6 on cylinder 4; Ford Escape 199 lone, 27 on cylinder 4 and 82 on cylinder 2. These are complaint counts, not failure rates. ------------------------------------------------------------------------------ 2c. A RANDOM 50, READ IN FULL (p0304-random-50-read.csv) ------------------------------------------------------------------------------ 50 of the 345 (sorted by ODI number) were drawn with Python random.seed(20260925); random.sample(rows, 50), and each read in full. P0304 only inside a quoted code range or list, not stored 15 of 50 the car really stored P0304 35 of 50 Of the 35 (one primary code per report): not diagnosed or not resolved 12 coolant or head gasket 10 valvetrain or cylinder head 4 rings or oil consumption 4 engine failed, cause not stated 4 ignition parts (trouble continued) 1 -> inside the engine (coolant, valvetrain, rings, engine) 22 parts fitted before the cause was found 8 engine stopped or lost power while moving 8 (11 of 50) One reader, one pass, no second coder. At n=35 a share near one half carries a 95% margin of about +/-17 points. ------------------------------------------------------------------------------ 3. OWNER-REPORTED AMOUNTS (p0304-owner-reported-amounts.csv) ------------------------------------------------------------------------------ Every dollar figure between $40 and $25,000 in the 345 narratives (92 figures) was read in context. 42 belong to this code's repairs, by lane: ignition parts and carbon cleaning (4) $357 to $1,023 fuel injectors, Honda (9) $899.19 to $2,000 piston rings to short block, Honda V6 (5) $1,000 to $12,000 cylinder head, Jeep 3.6L (2) $3,700 to $4,850 lifters, followers, engines, GM (3) $4,300 to $10,479.57 coolant intrusion, Ford EcoBoost (17) $4,700 to $11,000 head gasket or engine, other (2) $4,000 to $8,001.88 Excluded: transmissions, tows, loans, diagnostics and unrelated work. ------------------------------------------------------------------------------ 4. DOCUMENTS (p0304-recalls-extensions-bulletins.csv) ------------------------------------------------------------------------------ Full-text search of manufacturer communications for P0304 and for cylinder 4 wording ("cylinder 4", "no. 4 cylinder", "#4 cylinder" and variants): 636 documents. Most list P0304 inside a range of cylinder codes; the CSV keeps the ones that single out cylinder 4 or a group of cylinders including it, plus the extensions and programs that cover P0304 repairs. No NHTSA safety recall from 2010 names P0304. ------------------------------------------------------------------------------ 5. PRICES AND LIMITS ------------------------------------------------------------------------------ Price ranges marked as estimates in the article are US shop estimates carried from PulsCar's repair guides, verified July to September 2026. Complaints are self-reported and over-represent bad outcomes. Nothing here is a failure rate.