Hi Guys Last month the Megs started misfiring. Initially the problem was under boost, felt like a spark issue where engine power was limited and stuttering. Scanned it with OBD and found the following: Car Scanner ELM OBD2 Version: 1.118.0/401180/GP DTC report Connection profile: Renault Renault Megane III RS [EN]Date: 3/05/2025 6:07:35 PM VIN: VF1DZY106D0683673 ============================ OBD-IIOBD-II DTCs: 11 ---------------------------- P0303 [0x0303] Cylinder 3 - misfire detected Status: Confirmed ---------------------------- P0300 [0x0300] Random/multiple cylinder(s) - misfire detected Status: Confirmed ---------------------------- P0304 [0x0304] Cylinder 4 - misfire detected Status: Confirmed ---------------------------- P0130(11) [0x013011] Archive (inactive) Heated oxygen sensor (HO2S) 1, bank 1 - circuit malfunction Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0301(F8) [0x0301F8] Archive (inactive) Cylinder 1 - misfire detected Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0302(F8) [0x0302F8] Archive (inactive) Cylinder 2 - misfire detected Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0303(F8) [0x0303F8] Archive (inactive) Cylinder 3 - misfire detected Status: Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0304(F8) [0x0304F8] Archive (inactive) Cylinder 4 - misfire detected Status: Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0300(F8) [0x0300F8] Random/multiple cylinder(s) - misfire detected Status: Test failed, Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0313(F8) [0x0313F8] Archive (inactive) Misfire detected - low fuel level Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0130(09) [0x013009] Archive (inactive) Heated oxygen sensor (HO2S) 1, bank 1 - circuit malfunction Status: Test failed since last DTC clear, Test not completed during this operation cycle ============================ Engine control unit (11 bit)Engine control unit (11 bit) DTCs: 8 ---------------------------- P0130(11) [0x013011] Archive (inactive) Heated oxygen sensor (HO2S) 1, bank 1 - circuit malfunction Odometer: 95648 km Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0301(F8) [0x0301F8] Archive (inactive) Cylinder 1 - misfire detected Odometer: 198955 km Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0302(F8) [0x0302F8] Archive (inactive) Cylinder 2 - misfire detected Odometer: 174665 km Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0303(F8) [0x0303F8] Archive (inactive) Cylinder 3 - misfire detected Odometer: 209526 km Status: Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0304(F8) [0x0304F8] Archive (inactive) Cylinder 4 - misfire detected Odometer: 209526 km Status: Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0300(F8) [0x0300F8] Random/multiple cylinder(s) - misfire detected Odometer: 209538 km Status: Test failed, Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0313(F8) [0x0313F8] Archive (inactive) Misfire detected - low fuel level Odometer: 99926 km Status: Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0130(09) [0x013009] Archive (inactive) Heated oxygen sensor (HO2S) 1, bank 1 - circuit malfunction Odometer: 52192 km Status: Test failed since last DTC clear, Test not completed during this operation cycle ============================ ABS control unit (11 bit) No DTC found. ============================ Dashboard/Instrument cluster (11 bit) No DTC found. ============================ Heater & air conditioning (11 bit) No DTC found. ============================ BCM (11 bit) No DTC found. ============================ EMM (11 bit) No DTC found. ============================ Emergency Call and Communication Module (11 bit) No DTC found. Car was sent to French Car Care who found oil leaking into the cylinder head from a busted breather hose, replaced the breather hose and cleaned the oil out of the head, replaced the plugs, coil packs, injectors, rewired the entire loom for all these components, changed the fuel filter and pump, air filter and oil. Compression test came back all 4 cylinders above 150. Picked the car up today, mechanic said it should be all good after running for a while and told me to floor it to clear any congestion in the fuel system. This did not work, the car barely ran and long story short, I put an OBD reader on it and found I was running on 2 cylinders all the way home. Scanned with OBD when I got home and it returned the following. Car Scanner ELM OBD2 Version: 1.118.0/401180/GP DTC report Connection profile: Renault Renault Megane III RS [EN]Date: 5/30/2025 8:25:55 PM VIN: VF1DZY106D0683673 ============================ OBD-IIOBD-II DTCs: 11 ---------------------------- P0304 [0x0304] Cylinder 4 - misfire detected Status: Confirmed ---------------------------- P0302 [0x0302] Cylinder 2 - misfire detected Status: Confirmed ---------------------------- P0300 [0x0300] Random/multiple cylinder(s) - misfire detected Status: Confirmed ---------------------------- P0136 [0x0136] Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction Status: Pending ---------------------------- P0136(13) [0x013613] Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction Status: Pending, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0302(F8) [0x0302F8] Cylinder 2 - misfire detected Status: Test failed, Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0302(66) [0x030266] Cylinder 2 - misfire detected Status: Test failed, Pending, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0304(F8) [0x0304F8] Cylinder 4 - misfire detected Status: Test failed, Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0304(66) [0x030466] Cylinder 4 - misfire detected Status: Test failed, Pending, Test failed since last DTC clear, Test not completed during this operation cycle ---------------------------- P0300(F8) [0x0300F8] Random/multiple cylinder(s) - misfire detected Status: Test failed, Test failed (current drive cycle), Pending, Confirmed, Test failed since last DTC clear ---------------------------- P0300(66) [0x030066] Random/multiple cylinder(s) - misfire detected Status: Test failed, Pending, Test failed since last DTC clear, Test not completed during this operation cycle ============================ Engine control unit (11 bit) No DTC found. ============================ ABS control unit (11 bit) No DTC found. ============================ SRS/Airbags (11 bit) No DTC found. ============================ Power steering (11 bit) No DTC found. ============================ Dashboard/Instrument cluster (11 bit) No DTC found. ============================ Heater & air conditioning (11 bit) No DTC found. ============================ BCM (11 bit) No DTC found. ============================ EMM (11 bit) No DTC found. ============================ Sonar (11 bit) No DTC found. ============================ Emergency Call and Communication Module (11 bit) No DTC found. So the Lambda/Oxy sensor issue jumped from one to the other, now I'm stuck wondering if it's the sensors that are faulty or the catalytic converter itself.... or something else entirely. The car barely runs, stuttering consistently through the rpm range. Engine light is flashing repeatedly. Under deceleration the car sounds perfect, no indication of engine damage, no knocking or strange noises at all (besides an annoying vibrating heat shield). Has anyone suffered a similiar issue? If so I'd like to know how this was resolved, as I don't want to replace parts blindly. Thanks Guys
Message Ianplymouth on here, he will probably be able to help you. If not, try the facebook forums, its a more active sight.. Let us know how you get on.