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p0420
1-4 of 4 Results
  1. Maintenance & Care
    My P0420 CEL code came up again after replacing my downstream O2 sensor a few months back. There has been no diminished engine performance, but my gas mileage was really poor 18-20mpg combined. Also an oil leak has flared up in front of the cylinder head by the valve cover. Even though I...
  2. Help!
    I've been having some trouble with my exhaust since the Fall. The flex portion of my exhaust rusted out so I replaced it with another flex pipe and clamped it in. I had to slip it in between the original portion of the flex pipe because otherwise the 02 sensor looks like it would have to be...
  3. Maintenance & Care
    So my 2003 Elantra has been getting horrible gas mileage, running super rich. I had a constant P0420 catalytic emissions code and one misfire reading. I'd clear it and it'd go away for about an hour and come back. I feared I would have to replace my whole exhaust manifold/cat part until I read...
  4. Help!
    I know you guys have heard it ten thousand time already, but I have the P0420 code. What I'm wondering is if this leads to acceleration issues or not? What happens is if I press the gas too hard, the engine loses power, won't accelerate, but if I back off the gas, WHOOSH and it flies. Extremely...
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