jrobinson Posted March 3, 2019 Share Posted March 3, 2019 Hi all, My Ford Fiesta 2007 16v recently had the engine management light come on. I had noticed that the car had started to judder a bit a week or two before the light came on. When I got home from work, I plugged in the ODBII reader and discovered this error: P0304 Cylinder 4 Misfire Detected I did a quick troubleshoot, inspected the spark plug and the HT Lead as well as the top of the ignition coil. All seemed visually fine. I also switched the spark plug from cylinder 4 into cylinder 1. Ran the car and checked the OBDII reader again. I got the same error code (P0304). I noticed this time however, that there was a code pending too. When I checked it was P0301 Cylinder 1 Misfire Detected. (This may have been there during my original test but I did not notice it). I would love some advice from you more experienced folks: Do Cylinders one and four work as a pair? If so, and I am receiving faults for both, what does this suggest the problem may be? Could it be the initiation coil at fault? If so, how would I check? Thank you in advance for your help, I really appreciate it! James Quote Link to comment Share on other sites More sharing options...
nashdm2 Posted March 3, 2019 Share Posted March 3, 2019 If you moved the spark plug from cylinder 4 to 1 and then the fault code also moved from cylinder 4 to 1, then surely that means the spark plug is faulty, unless I have missed something? Quote Link to comment Share on other sites More sharing options...
Nick_T Posted March 3, 2019 Share Posted March 3, 2019 As above this would probably indicate a duff plug, for the sake of a tenner I would stick a new set of plugs in.... Quote Link to comment Share on other sites More sharing options...
jrobinson Posted March 3, 2019 Author Share Posted March 3, 2019 2 hours ago, nashdm2 said: If you moved the spark plug from cylinder 4 to 1 and then the fault code also moved from cylinder 4 to 1, then surely that means the spark plug is faulty, unless I have missed something? Sorry, I'm not sure if I explained myself properly. I did move the spark plug from cylinder 4 to 1 but I'm still getting the error on cylinder 4 as well as an error pending on cylinder 1 according to the OBD reader. Quote Link to comment Share on other sites More sharing options...
isetta Posted March 3, 2019 Share Posted March 3, 2019 Did you definitely clear all fault codes when you changed spark plugs around before you restarted the engine? Quote Link to comment Share on other sites More sharing options...
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