I have a 2003 Maxima SE AT with about 130,000 miles on it. I just got a bluetooth OBDII scanner and I've downloaded Car Gauge Pro and Torque Pro. I was curious what PIDs should I be looking at to know if my car is running efficiently.

I ask because at my last smog check in 2011 (I'm in CA) the smog guy mentioned that my HC (measured 30 when the ave. was 4) and CO(%) (measured .19, when the ave. is .01) were a bit high but not high enough to fail. My NOx was 0 when the ave. is 16.

I had already replaced my primary O2 sensors a couple months before the test and had new plugs put in about a year before the test. I also replaced the MAF (did the swap you see on the ORG)

I also don't feel like I'm getting the MPG that I used to get. It actually seemed to go down AFTER my new plugs. I didn't put them in so I'm not sure what was installed.

I have a rear valve cover leak that I'm going to fix in a couple weeks and I plan on putting in NGK iridium ix plugs. I have also just replaced my VIAS solenoid valve (had a ghost code).

While I'm changing the plugs should I replace the knock sensor since I'm have the UIM off? Anything else I should do while in there?

Just looking for a little advice on what I should be monitoring so I can make sure everything is running as efficiently as they should.

Thanks!

EDIT: Forgot to mention the car runs smoothly and idles perfectly and no other codes pulled since replacing my VIAS solendoid.

 

say bye to the cats and show them no mercy

 

I live in California so I don't think I can say bye to my cats. Are you saying that this is an indication that my cats are going bad?

I'm a relative noob and still learning. If my cats are going I better start saving my money because that's an expensive job here in Cali.

 

That's an expensive job anywhere. Probably more so in Commiefornia.

But yes, with everything else working properly the performance of the catalyst is probably degrading. The only way to fix that would be to replace the catalytic converters. This isn't keeping your car from running efficiently though unless they are clogged. Could also be burning excessive oil, or the A/F mixture could be off. But most likely it's your old cats.

 

Gut plus O2 sim = success (what a bull**** state)

It's a guarantee that they're going bad b/c every single one will fail. Mine disintegrated at 75k. Driving like a grandma will prolong their life, but it's inevitable. They clog and fall apart.

 

I was hoping I didn't have to replace the cats. I wonder if I do this, do I just replace all of them or find a way to see which one is bad. I don't have any codes yet and I wonder if I should just wait for a code or do a preemptive strike?

I burn about what is average for a 2003 max but I do have that rear valve cover leak I have to fix.

How can I check to my A/F mixture? Is this something I can do with my new OBDII scanner?

Thanks for the info, just trying to learn as much as I can. This org and it's members really help a lot.

I don't plan on gutting, I would rather not do that. I don't mind spending the money if it means I can drive the car another 100,000 miles.

 

Which iiiissss?

 

sorry, i knew i forgot something...

I'd say about 1 quart maybe a little more between my oil changes which is between 3,000 to 5,000 miles. I'm not too scientific with it, just keep an eye on it every month or so.

And I do have that oil leak with my rear valve cover, which I just discovered a few weeks ago. I never noticed it until a mechanic had it up on a lift and pointed it out to me.

 

Yeah, sounds about right. I burn a half quart every 3k. Change the oil every 8k or so. Change the filter at about 4-5k.

Adding roughly 1.5-2 quarts per 8-10k.

 

NmexMAX - you've always been extremely helpful when i've posted a question.

could you point me in the right direction on checking my A/F ratio to make sure things are running well. i have an OBDII scanner and torque pro app on my phone.

also, do you know how to check which cat could be going bad or would i just replace all cats? i have no codes or pending codes.

thanks!

 

Lapdog....check the West Coast forum. There is a thread in there about new regulations for the emissions. From what I understand this includes no more sniffer test. Instead they will do a visual check of your components and hook it up to an OBII tester to check for any engine codes.

With that...you can gut the cats and get O2 sims to pass. Provided the O2 sims look like OE.

 

You can gut your PRE cats in the Y pipe. The main cat just replace.

 

You need an AFR gauge... Maximum efficiency will be obtained at around 16:1... but EPA requires cars to run with an A/F ratio of 14.7:1 so the catalytic converter would work at maximum efficiency...

 

Thanks everyone. i'm going to start doing some research. appreciate the time you guys took to help me out!