Nissan Forum banner
1 - 10 of 10 Posts

· Registered
Joined
·
136 Posts
Discussion Starter · #1 ·
Seems my shotgun method took care of all the rough idle, etc....and I now have an intermittent P0420. I can clear the code, and as long as i don't hard accelerate - especially at 70mph+, then no code. I am guessing the hard, rough drive home when the rough idle initially happened probably pumped a bunch of unspent gas into the exhaust.

After reviewing all kinds of articles about P0420 / P0430 I am not clear on how to accurately determine if its the O2 sensor or the cat. My logic would take me to replace the O2 as it is (A) cheaper, and (B) much less involved to remove and replace. And, if replacing the O2 isn't the fix, then I would go the route of replacing both cats (L+R) and the left side O2 as well. (the cats were replaced about 8 years back)

One way is about $100 the other much much more $$$.

Any thoughts?
 

· Registered
Joined
·
82 Posts
If the cats were replaced 8 years ago......chances are that they are still good. Both cats failing at the same time is unlikely. Aftermarket USA catalytic converters have to be effective for a minimum of 5 years (DOT & FEDERAL emissions standards).

Record your o2 numbers while the engine is operating under Open Loop operation and place the data here for interpretation.
 

· Registered
Joined
·
136 Posts
Discussion Starter · #5 ·
Give it time......you installed alot of parts on the rig to eliminate a lot of unwanted situations. Give the computer time to make its own adjustments to your driving style......see what happens.
I was wondering about that. Prior to this P0420 - there were P0305, P0302, and P0300. I have replaced ALL coil packs and injectors, PCV valve, and the left side camshaft sensor, Additionally, a couple-two-three hoses were replaced as they were either split out at the ends - or were showing signs of splitting.

What drives me crazy with the P0420 is that it comes and goes, I am assuming that if the SEL goes out - AND no codes are stored or pending - then it is not an issue. I am not familiar with specific conditions that would trigger the code - or extinguish it.
 

· Registered
Joined
·
82 Posts
What drives me crazy with the P0420 is that it comes and goes, I am assuming that if the SEL goes out - AND no codes are stored or pending - then it is not an issue. I am not familiar with specific conditions that would trigger the code - or extinguish it.
l
I wouldn't worry about the P0420 code. I mean, I mean, with all those new parts, the computer needs time (drive cycles & heat cycles) to get things sorted out.

The reason why a SEL will turn off is because the PCM has recognized enough consecutive heat cycles with acceptable catalytic threshold performance.
 

· Registered
Joined
·
136 Posts
Discussion Starter · #7 ·
And i think you just might be right on target! I've had to make some runs into town, and so far - no codes. I even took her up to 80+mph - gradually - and no code. I figure i'll go a few more trips before I do the passing gear routine - and i've got my fingers crossed!
 

· Registered
Joined
·
136 Posts
Discussion Starter · #8 ·
I hoped that some additional miles would allow things to mellow out...but, P0420 still pops up now and then - but only on higher speed 70+ or a hard acceleration at moderate speed. And while I wished the code would just go the hell away, I am coming to terms with my future including new cats and sensors both sides. #[email protected]%*!
 

· Registered
Joined
·
3,822 Posts
You could try some Cataclean, or a sensor spacer if that doesn't help (provided you're not in an inspection state). If a cat is completely dead, P0420/P0430 will usually pop up like clockwork after two drive cycles. The fact that your P0420 pops up on-and-off indicates the cat probably has a little life left. If you go with a spacer, just be aware that it basically disables your early warning system, and a melted cat on a Miller-cycle Nissan engine can be catastrophic. So it's a good idea to pull out an IR thermometer and check the cat's temperature periodically when using spacers. When a cat is lit, the inlet temperature will always be lower than the outlet if the cat is alive. If the outlet is equal or less then it's in danger territory and it's time to ditch the spacer and replace the cat.
 

· Registered
Joined
·
136 Posts
Discussion Starter · #10 ·
"The fact that your P0420 pops up on-and-off indicates the cat probably has a little life left. "

Fully agree that "life" is running out on that cat. It is still throwing the code randomly.

If I remember correctly, both front cats have to unbolt to slide the exhaust backwards for access. In that, I think I will plan on replacing both cats as they are now over 10 years old. Granted, I don't drive the mileage I used to....but for a couple hundred more, both sides are new. Haven't decided whether to replace the upstream O2 sensors or not. I'm thinking replacing the O2's falls into that "while you have it all undone..." category.
 
1 - 10 of 10 Posts
Top