Elisa Posted March 7, 2022 Report Share Posted March 7, 2022 I have replaced all 6 spark plugs and coil packs. Yet, my spark plugs continuously misfire and I have replace #5 on three occasions in the past 4 months. What is the cause of the continuous misfire on 5? What does PO420 mean? I have replaced the catalytic converter 11 months ago. Could the spark plug misfire be related to a cylinder issue? Quote Link to comment Share on other sites More sharing options...
John/Horace Posted March 7, 2022 Report Share Posted March 7, 2022 Welcome to forum. Yes it could be a cylinder issue, compression if too low can cause misfire. A bad injector, not very common thing, could also cause misfire issue. Intake manifold seals if leaking air can also cause misfire codes. CPS crank position sensor which is a wear item at high milage, can cause misfire codes; although stalling engine is more common symptom. Lots of potential causes for misfire, unfortunately. Quote Link to comment Share on other sites More sharing options...
tsteves5 Posted March 7, 2022 Report Share Posted March 7, 2022 P0420 is a detected issue with the Bank 1 (rear/firewall side) catalytic converter efficiency. Unfortunately, a misfiring cylinder can damage a cat. I had a difficult misfire issue on a Town and Country (with the same 3.6 V6) a while back. Replaced plugs, coils, fuel injector, crank position sensor, and checked manifold leaks. None of those fixed it. Ended up doing a leak down test. Found a ton of air bypassing the piston. Ended up being a bad piston ring. I hope that you don't have that issue. Quote Link to comment Share on other sites More sharing options...
Elisa Posted March 7, 2022 Author Report Share Posted March 7, 2022 @tsteves5 - Thanks for your response. Was it an expensive piston ring fix? Quote Link to comment Share on other sites More sharing options...
tsteves5 Posted March 7, 2022 Report Share Posted March 7, 2022 (edited) 1 hour ago, Elisa said: @tsteves5 - Thanks for your response. Was it an expensive piston ring fix? It was cheaper to install a new (used) engine. Edited March 7, 2022 by tsteves5 Quote Link to comment Share on other sites More sharing options...
Elisa Posted March 12, 2022 Author Report Share Posted March 12, 2022 @John/Horace Thank you for the guidance. I have been reviewing similar concerns on this site. Has anyone heard of the extended warranty that Dodge had released regarding a known cylinder issue that causes the continued replacement of spark plugs (misfires)? I believe it’s 10 years or 150k. It’s not a recall which makes it difficult to track. At least for me. I want to research that further as well. I was certain that I had read info. on a thread on this site. Quote Link to comment Share on other sites More sharing options...
2late4u Posted March 12, 2022 Report Share Posted March 12, 2022 (edited) https://static.nhtsa.gov/odi/tsbs/2014/MC-10069161-0335.pdf 2011 12 13 model yrs,,, from google for more info contact your local dodge dealership Edited March 12, 2022 by 2late4u Quote Link to comment Share on other sites More sharing options...
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