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Discussion Starter · #1 ·
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 hard to do in 3rd, way, WAY too easy to hit in 2nd and 1st. It's driving me nuts! I hooked up a tool and the only code is the P0420. If I hold down the gas in this state, it still won't go, but the CEL flashes, still doesn't throw any other codes tho. Is this "normal"?

I've tried my very, very hardest to come up with any and all information I could. I spoke to mechanics, the guy who sold me the car, co-workers, searched the forum, ran a logger scan-tool on my car, and I've come to the conclusion that I can't fix this. I can't find any other reason why it would do this weird power loss thing.

The previous owner ran the mileage too high and now I'm ineligible for the Catalytic Converter replacement TSB (otherwise I'd go right to the dealer). I'm not buying a new Cat, because I just passed an E-test. I was far under the limit and now have another 2 years before it's needed again.

So that being said, I'm looking at the "non-fouler on the end of the o2 sensor" trick and if that doesn't work I'm gonna cut the harness, hook a voltage divider circuit up to the sensor lead, and put a resistor on the heater circuit. Do you think that the removal of this code will prevent the ECU from cutting back on me?

Any input would be greatly appreciated, thanks in advance.
 

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Discussion Starter · #4 · (Edited)
No, not plugged, the car wouldn't do highway speeds if it were plugged. That happened on my Ranger and I had to have my foot to the floor in all gears to go anywhere.

So, I reiterate: I feather the gas pedal and it takes off, push too hard and it's like you're not pressing the gas at all. This limit rises as engine RPMs rise, and if you press past that point for too long (even though you're slowing down at this point), the CEL starts flashing. But it doesn't show any other codes. As you bring your foot off the pedal you get this burst of power from the engine as you pass that point again. It's wierd to drive like this, please help.

So how do I get myself out of this horrid limp mode! I have a catalytic converter, honest! I'm not trying to cheat but I thank Hyundai for accusing me of doing so. What do I do to restore normal driveability? ANY ideas would be greatly appreciated.
 

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Discussion Starter · #6 ·
OK, so it IS the second O2 sensor. I think I might just wrench the thing off and put a spacer (or two) on it then. Do I have to do anything out of the ordinary to reset the CEL Light? Like is there a "limp mode reset" that has to be done after the light is off?
 
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