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Hi everyone, so i just picked up a 04 frontier with the 3.3 and i just did a tuneup on it last weekend. When i bought it, it had codes for a evap leak and the knock sensor. Ive since fixed those issues and did a tuneup with denso plugs pregapped to .040. I thought i had read somewhere that the recommended gap was .039-.044 so i didn't think anything of it, but now i am getting alternating p0420 and p0430 codes. These codes were not showing up when i first bought the truck so i feel like it is something i did. I did do a major tune up which involved timing belt water pump, plugs, wires, cap, rotor, etc. Do you guys think that my plugs could be the issue? Do i need to yank them out and regap them? Thanks
 

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The gap should be .044" and I would have a hard time believing that would cause your catalyst codes. I would have rather heard that you put NGK #2647 plugs in it, which are the original equipment plug. Denso makes quality plugs, but I don't use anything but NGK sparks in anything I own. If the timing belt was put on a tooth off, it could cause catalyst codes. If that were the case, you probably would have noticed it when you checked the ignition timing and found that you had to turn the distributor to the far end of the adjustment range. Try re-gapping the plugs or even reinstalling the old ones if you haven't trashed them, already, and go from there.
 

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The gap should be .044" and I would have a hard time believing that would cause your catalyst codes. I would have rather heard that you put NGK #2647 plugs in it, which are the original equipment plug. Denso makes quality plugs, but I don't use anything but NGK sparks in anything I own. If the timing belt was put on a tooth off, it could cause catalyst codes. If that were the case, you probably would have noticed it when you checked the ignition timing and found that you had to turn the distributor to the far end of the adjustment range. Try re-gapping the plugs or even reinstalling the old ones if you haven't trashed them, already, and go from there.
Thanks! I'll be honest i didn't do much research on this truck. I bought it and then that night i just sat on rockauto's website and started clicking through all their parts. Denso came to mind because i know they make oem parts for some manufacturers. I did read through the service manual and realized that i never checked the timing. Just checked it earlier and found it was sitting at 5 degrees! I just readjusted it to 10 degrees as per service manual. I hope this was the issue as i really don't want to deal with the plugs again. I happened to do them when the intake manifold was off. They look like a pain to do with it on.
 

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The only one that is a pain is the spark plug for cylinder #6; the rest aren't too bad. If you lined up the lines on the new timing belt correctly with cam sprocket marks, it should be in time. The dashed line matches to the right bank (passenger side) cam sprocket mark at the 11:00 position and the solid lines match to their respective marks on the left cam sprocket (@ 1:00 position) and crank sprocket (@ 5:30 position), with the arrow on the belt facing towards the front of the vehicle. The hold down bolt on the distributor will typically sit just a hair off of dead center within the adjustment slot. If it sits at the far end of the adjustment slot, it is usually an indication that the engine timing is off (timing belt off a tooth).
 

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The only one that is a pain is the spark plug for cylinder #6; the rest aren't too bad. If you lined up the lines on the new timing belt correctly with cam sprocket marks, it should be in time. The dashed line matches to the right bank (passenger side) cam sprocket mark at the 11:00 position and the solid lines match to their respective marks on the left cam sprocket (@ 1:00 position) and crank sprocket (@ 5:30 position), with the arrow on the belt facing towards the front of the vehicle. The hold down bolt on the distributor will typically sit just a hair off of dead center within the adjustment slot. If it sits at the far end of the adjustment slot, it is usually an indication that the engine timing is off (timing belt off a tooth).
Thanks. The distributor is now just a tad off center. The PO had it almost maxed out in one direction. When I did the timing belt the original was very loose. I hope that fixed my issue.
 

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the 420 and 430 codes are tripped from the downstream O2 sensors, the most common causes are exhaust leaks, cracked exhaust manifolds , leaking gaskets etc.

since you are getting both banks showing a code, I would also check all the ground wires, everywhere, on the chassis and on the block, and the ones on the exhaust system as well...
 

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The key grounds to check would be the EGI grounds, located on the intake plenum. There will be two, 10MM head bolts securing several black wires. Remove the bolts, clean the contact area on the plenum and the eyelets and reinstall.
 

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thanks. I will drive it around and see if the code pops back up. the 2 codes never came on at the same time. I guess i cleared the codes too soon each time.
 
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