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Bill_Crosby, UK Car Mechanic
Category: UK Car
Satisfied Customers: 3307
Experience:  City & Guilds Vauxhall Master Technician & Auto Electrician Since 1993
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renault megane 04 engine misfire! not coil as removing any

Customer Question

renault megane 04 engine misfire! not coil as removing any lead produces the same reaction 1st o2 sensor voltage dances all over the place second o2 sensor stable code reader says 13 o2 sensor wiring circuit
Submitted: 8 years ago.
Category: UK Car
Expert:  badj replied 8 years ago.

Hi there,


Once the engine is warm, the 1st O2 sensor voltage should switch between 0.8v and about 1.2v - If it is switching to extremes (0v to 1v etc.) and the 2nd O2 sensor is reading low (about 0.4v ish) then you are probably looking at a faulty 1st O2 sensor.


I have experienced this on newer Renaults in the form of a Lean misfire (foot down, car hesitates and seems asthmatic). Usually seen in conjunction of the emissions light. New O2 sensor in this case works a treat.


Best of luck



Customer: replied 8 years ago.
no i replaced the 1st o2 sensor this morning @ £90 and everything is still the same
Expert:  Bill_Crosby replied 8 years ago.

Good evening, I hope I can help you.


What engine size do you have and do you have any 'P' codes from the code reader .




Customer: replied 8 years ago.
Hi its a 1.6 and i have no p codes just 13 o2 sensor circuit
Expert:  Bill_Crosby replied 8 years ago.

Hi again. First off all the front O2 sensor should as you say dance all over the place. It should vary between 0.2v and 0.8v. The rear sensor should be more stable with its reading of approx 0.7v.


Usually a misfire like yours, where you cannot determine what cylinder is at fault, eg removing plug leads and misfire doesnt change is normally caused by an air induction leak. You could try spraying WD40 around the manifold gasket area and vacuum hoses to see if that alters engine sound.



Customer: replied 8 years ago.
Ok I will try wd40 and get back to you tomorrow
Cheers Rick!!
Customer: replied 8 years ago.
Hithere! i sorted it but i has taken all day!!!the catalitic converter was blocked solid