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28/12/2020 1:29 pm
Topic starter
- 2002 dodge dakota 5.9 magnum v8 140k miles. I've got a PO420 cat code but from my knowledge a lot of things can cause that code to go off. It has a slight misfire but I havent had any codes for it yet. You can hear it puffing at the exhaust and is also running rich, smell of gas is very apparent at the tailpipes. Has one cat converter 2 o2 sensors and a muffler that duals out the back. Downstream o2 sensor is new. 8 new spark plugs, compression test was fine, lowest dry pressure was 2 cylinder back from the passenger side I got 120 pounds dry. From what I've researched thats still within spec. MAP sensor seems to be working, unplugged it and the idle got worse. New pcv valve as well, going to get the old o2 sensor changed tomorrow and see if that fixes it. If not moving to replace all injectors and regulator, any ideas scotty? Also burns a bit of oil at high rpm im not sure if the new pcv valve fixed it or not.
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28/12/2020 2:22 pm
You have to check the upstream and down stream O2 sensor by graphing them side to side. Normally your upper o2 will show activity and if the cat is anything good..the down stream cat will show hardly any activity meaning it is efficient and working...but if it has activity then it is not efficient and NOT doing its job. if it shows as much activity as the upper stream O2...its a goner
If you had missfires and they were going on for a long time it destroys the CAT eventually. Missfires usually show up in the Missfire menu on a scanner. Basically the missfire indicated to the ECM that one cyl has slowed compared to the others and thats how the ECM tags the slow cyl number.
