# US 2018/0023531 A1 · Spark plug fouling detection for ignition system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0023531 A1 - Document ID: US20180023531A1 - Status: Published application - Kind: A1 - Application number: 15/722,867 - Filed: 2017-10-02 - Published: 2018-01-25 - Earliest claimed: 2013-12-19 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Chris Paul Glugla; Garlan J. Huberts; Nelson William Morrow; Qiuping Qu - Web page: https://patentgrep.com/patent/US20180023531A1 ## CPC - F02P 17/12: Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60) - F02P 3/0456: {using digital techniques} - F02P 17/10: Measuring dwell or antidwell time - F01N 11/00: Monitoring or diagnostic devices for exhaust-gas treatment apparatus - F02B 2075/125: {Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber} - F02D 41/1441: {Plural sensors} - F02D 41/1454: {the characteristics being an oxygen content or concentration or the air-fuel ratio} - F02D 41/1495: {Detection of abnormalities in the air/fuel ratio feedback system} - F02D 2041/227: {Limping Home, i.e. taking specific engine control measures at abnormal conditions} - F02D 2041/228: {Warning displays} - F02P 2017/121: {by measuring spark voltage} - Y02T 10/12: Improving ICE efficiencies - F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00) - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Methods and systems are provided for determining a type of spark plug fouling. In one example, a method may include differentiating spark plug fouling due to soot accumulation from spark plug fouling due to fuel additive accumulation based on a current on a control wire of the spark plug following application of a dwell command. Further, exhaust oxygen sensor degradation and/or exhaust catalyst degradation may be determined based on switching frequencies of one or more exhaust oxygen sensors and the type of spark plug fouling. ## Claims ### Claim 1 A method for an engine comprising: for each combustion event of a cylinder of the engine, outputting a dwell command on a control wire of a spark plug ignition coil; estimating an ignition current switching time taken for a current of the control wire to drop below a pre-determined value; counting a fraction of combustion cycles of the cylinder over a given vehicle drive cycle that have the ignition current switching time longer than a threshold duration; and indicating fouling of the cylinder's spark plug due to fuel additive accumulation on the spark plug based on the fraction being larger than a threshold percentage. ### Claim 2 (depends on 1) The method of claim 1, further comprising estimating an average ignition current switching time for the cylinder over a number of combustion cycles of the given vehicle drive cycle. ### Claim 3 (depends on 2) The method of claim 2, further comprising, in response to the estimated average ignition current switching time being longer than a threshold time, indicating spark plug fouling due to fuel additive accumulation on the spark plug of the cylinder. ### Claim 4 (depends on 3) The method of claim 3, wherein the duration is a threshold duration based on the dwell command applied and an operational status of a current sink. ### Claim 5 (depends on 3) The method of claim 3, wherein the threshold percentage is based on an average percentage in an engine operating with a fuel not including fuel additives. ### Claim 6 (depends on 3) The method of claim 3, further comprising operating with the fraction smaller than the threshold percentage, and in response to the fraction being smaller than the threshold percentage, increasing an engine idling speed and engine load, and advancing spark ignition timing of the cylinder to maintain a tip temperature of the spark plug above a threshold temperature for a threshold duration. ### Claim 7 (depends on 6) The method of claim 6, further comprising; after the threshold duration, reassessing the fraction of combustion cycles of the cylinder. ### Claim 8 (depends on 7) The method of claim 7, further comprising in response to the reassessed fraction being smaller than the threshold percentage, indicating spark plug fouling due to soot accumulation. ### Claim 9 (depends on 1) The method of claim 1, further comprising, in response to the indication of spark plug fouling due to fuel additive accumulation, decreasing an engine load, and disabling fuel and spark for an adjacent cylinder configured to receive exhaust residuals from the cylinder coupled to the fouled spark plug. ### Claim 10 (depends on 1) The method of claim 1, further comprising estimating a response time of an exhaust oxygen sensor coupled upstream of an exhaust catalyst. ### Claim 11 (depends on 10) The method of claim 10, further comprising, based on the estimated response time being lower than a threshold, indicating degradation of the exhaust oxygen sensor due to fuel additive accumulation and confirming spark plug fouling due to fuel additive accumulation. ### Claim 12 (depends on 1) The method of claim 1, wherein the engine is a boosted engine. ### Claim 13 (depends on 1) The method of claim 1, wherein the engine is a direct injection fueled engine. ### Claim 14 A method for an engine comprising: boosting intake air delivered to the engine with a turbocharger; and for each combustion event of a cylinder of the engine, direct injecting fuel to the engine and outputting a dwell command on a control wire of a spark plug ignition coil; estimating an ignition current switching time taken for a current of the control wire to drop below a pre-determined value; counting a fraction of combustion cycles of the cylinder over a given vehicle drive cycle that have the ignition current switching time longer than a threshold duration; and indicating fouling of the cylinder's spark plug due to fuel additive accumulation on the spark plug based on the fraction being larger than a threshold percentage. ### Claim 15 (depends on 14) The method of claim 14, further comprising estimating an average ignition current switching time for the cylinder over a number of combustion cycles of the given vehicle drive cycle, and in response to the estimated average ignition current switching time being longer than a threshold time, indicating spark plug fouling due to fuel additive accumulation on the spark plug of the cylinder. ### Claim 16 (depends on 15) The method of claim 15, wherein the duration is a threshold duration based on the dwell command applied and an operational status of a current sink, and wherein the threshold percentage is based on an average percentage in an engine operating with a fuel not including fuel additives. ### Claim 17 (depends on 16) The method of claim 16, further comprising operating with the fraction smaller than the threshold percentage, and in response to the fraction being smaller than the threshold percentage, increasing an engine idling speed and engine load, and advancing spark ignition timing of the cylinder to maintain a tip temperature of the spark plug above a threshold temperature for a threshold duration. ### Claim 18 (depends on 17) The method of claim 17, further comprising; after the threshold duration, reassessing the fraction of combustion cycles of the cylinder. ### Claim 19 (depends on 18) The method of claim 18, further comprising in response to the reassessed fraction being smaller than the threshold percentage, indicating spark plug fouling due to soot accumulation. ### Claim 20 (depends on 14) The method of claim 14, further comprising, in response to the indication of spark plug fouling due to fuel additive accumulation, decreasing an engine load, and disabling fuel and spark for an adjacent cylinder configured to receive exhaust residuals from the cylinder coupled to the fouled spark plug.