Bad Cat
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From: Phoenix
Bad Cat
i have a 4 banger not a truck or a ford for that matter but most engine systems are very close to being the same so i pulled a p0421 code off of my car and its is very intermittent the code only comes on when the idle gets rough and then goes away for a few hundred miles the idle gets rough like the egr is stickin. so my question is can a stickin egr cause a p0421 engine code
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Don't just test the O2s, check the fuel trim. The trim is shown as a percentage. It should be less than 5%, ideally less than 2%. If the fuel trims are not near zero, there is a fuel management problem that much be resolved before replacing the cat. It is possible that the cat may begin working again if the condition is corrected. Fix the cause first.
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From: Phoenix
its actually a hyundai i bought second hand i replaced o2 sensors both pre and post cat cause it had some miles and the wires looked bad on the post cat o2 i am led to believe that it is something other than the cat though due to the fact that it is intermittent how it comes and goes
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From: Phoenix
i gave it a seafoam treatment a few days ago i know its not a fix but more of a maintenance item and i reset the computer and WOW it made a huge diff oh and i drove it 300 miles and no MIL/CEL came on. i feel as though perhaps i should use it more as a maintenance item every other oil change or every other other oil change
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Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Good idea. And my notes don't show a problem with that year of Hyundai. The only ones I see problems with are the Accent and the Elantra with the 1.5L, 1.6L or 2.0L motors from '99'-02
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