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Discussion Starter · #41 ·
Massachusetts safety inspection is fairly strict. Along with all that you mentioned, the state has several cameras monitoring the inspection... So, the shop I go to performs it to the tee, Big Brother is watching him... He even jacked up the front end to check for tie rod and bearing wear on my brand new 19's initial inspection. He caught that my '03 had a tiny bit of tie rod slop just before I traded it for my '19 Murano, so I got a rejection sticker (it's not legally drivable with a rejection sticker, but I only live a mile from the inspection station.) However, he TOTALLY missed the severe front subframe rot only inches away from where he was jacking up, lucky for me at the time, but bad from a safety inspection standpoint... Luckily I caught it myself about a week later, so I traded it for my '19. It was expensive to repair, about $1500-2000, not worth it for an '03 IMO.
That seems a little unrealistic, who is really gonna review all those videos??
 

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That seems a little unrealistic, who is really gonna review all those videos??
They're piped in real-time to the RMV. The inspection guy mentioned they are monitored, and can certainly be reviewed if an inspected car is involved in a safety related failure incident... Right or wrong, he was pretty spooked by them...
 
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New Jersey ended vehicle safety inspections back in 2010. Opponents for repealing the program asserted that traffic crashes would increase dramatically as a result. A few years later, NJ did a review and found no discernible change in the rate of safety-related traffic crashes. In fact, the few studies that looked at the effectiveness of safety inspection programs in general couldn't find a statistically-significant effect on traffic crashes (see this one for example that compared D.C. with NJ: It's No Accident: Evaluating the Effectiveness of Vehicle Safety Inspections by Alex Hoagland, Trevor Woolley :: SSRN).

The Government Accountability Office (GAO) also did a study on this a few years ago and while state officials claimed their programs increased highway safety (no surprise), GAO couldn't find any direct evidence for this and could not determine whether or not the costs of running these programs justified them (see publication GAO-15-705).

Frankly, I think these programs mainly just drive business to repair shops. Whenever a state talks about getting rid of safety inspections, the stakeholders that lobby the hardest against repeal are auto repair businesses. Programs like this cost money to run, even when private businesses are doing the inspections. If a public program is costing taxpayer dollars and can't be shown to have any direct benefit then it should be done away with, IMO.

Now, emissions inspections are another story and are well worth it (...and congratulations to the OP on passing).
 

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Discussion Starter · #44 ·
New Jersey ended vehicle safety inspections back in 2010. Opponents for repealing the program asserted that traffic crashes would increase dramatically as a result. A few years later, NJ did a review and found no discernible change in the rate of safety-related traffic crashes. In fact, the few studies that looked at the effectiveness of safety inspection programs in general couldn't find a statistically-significant effect on traffic crashes (see this one for example that compared D.C. with NJ: It's No Accident: Evaluating the Effectiveness of Vehicle Safety Inspections by Alex Hoagland, Trevor Woolley :: SSRN).

The Government Accountability Office (GAO) also did a study on this a few years ago and while state officials claimed their programs increased highway safety (no surprise), GAO couldn't find any direct evidence for this and could not determine whether or not the costs of running these programs justified them (see publication GAO-15-705).

Frankly, I think these programs mainly just drive business to repair shops. Whenever a state talks about getting rid of safety inspections, the stakeholders that lobby the hardest against repeal are auto repair businesses. Programs like this cost money to run, even when private businesses are doing the inspections. If a public program is costing taxpayer dollars and can't be shown to have any direct benefit then it should be done away with, IMO.

Now, emissions inspections are another story and are well worth it (...and congratulations to the OP on passing).
In PA, I'm certain that the state makes money from inspections because they regulate how much the inspections cost and they also issue the window display stickers. I'm sure they charge the inspection stations for the stickers and a percentage of each inspection. And of course the shops make money too. I know shops that literally turn away any true repair work. All they do is inspections, oil changes, and brake pads for the most part. Any other repairs are far and few in-between.
That's exactly why my murano was off of the road for so long. I literally had 4 shops turn me down. One guy quoted me $2500 hoping I would run. I called his bluff (because it was the same quote as the Nissan dealer) and said I would pay it so then he claimed that my murano had a whole bunch of other codes and I should just get rid of the car lol 😆
He even said that I could do it myself (which technically he wasn't lying) but considering he had a professional shop with all the tools he could possibly need he could have done it way faster than I did and easily made a good profit (I wouldn't have really paid the $2500 but he could have charged me say $500 on top of parts costs). He just simply didn't want to do the work lol

I think the states involvement as far as inspections is a reliable income stream that isn't considered taxes. Same with 50 dollar registration fees and drivers license renewals that don't even require you to do a written test let alone a driving test. In PA they also control all the liquor sales so I'm sure they have all of it accounted for before hand.

And BIG THANKS to you I Need Coffee. You really helped me out a whole lot with getting my murano back on the road. Can't thank you enough bro!!!!
 

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Discussion Starter · #45 ·
Update..... After about three weeks since I put everything back together BOTH CODES ARE BACK (P0420 and P0430)
Virtually all city/suburb driving with a little highway but no long or notable trips
So I changed pcv valve and since the intake plenum gasket was dirty and oily I changed that out too. Reset the codes. Both are back again.

According to live data on my scanner both upstream 02/AF sensors are reading right around 2.1 volts and both downstream O2 sensors are reading between .1 and .9 volts as the engine runs. From what I understand that's what they are supposed to be reading.
I have no idea why the code is being thrown if the O2 sensor are within range. I'm thinking maybe fuel injectors but Murano's have codes for air mixture that is too rich or also too lean (P0174)

I'm all out at this point... it must be the cats... maybe I got to them too late. I have no idea what else to try at this point smh
 

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At least you already pass your smog/inspection. I would try the anti fouler I mentioned earlier. You know, when you get those codes, the downstream O2 sensors are actually telling you that the CAT is not within specs. The sensors are not really defective because its reporting the readings its getting. The upstream A/F sensors really has nothing to do with those 2 codes. (wasted money in my view). When I added the anti fouler on my 99 odyssey with original exhaust system 240K, I used the same downstream O2 sensor and the code disappeared. Replacing the downstream O2 sensor is the last step/attempt in fixing those codes before replacing the expensive CAT. But there is that anti fouler trick you can try and see how it goes. You have a whole year before the next smog so lots of time to deal with it.
 

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Discussion Starter · #47 ·
At least you already pass your smog/inspection. I would try the anti fouler I mentioned earlier. You know, when you get those codes, the downstream O2 sensors are actually telling you that the CAT is not within specs. The sensors are not really defective because its reporting the readings its getting. The upstream A/F sensors really has nothing to do with those 2 codes. (wasted money in my view). When I added the anti fouler on my 99 odyssey with original exhaust system 240K, I used the same downstream O2 sensor and the code disappeared. Replacing the downstream O2 sensor is the last step/attempt in fixing those codes before replacing the expensive CAT. But there is that anti fouler trick you can try and see how it goes. You have a whole year before the next smog so lots of time to deal with it.
I just don't understand how that code is being thrown even tho the downstream sensors are with in range.
 

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Update..... After about three weeks since I put everything back together BOTH CODES ARE BACK (P0420 and P0430)
Virtually all city/suburb driving with a little highway but no long or notable trips
So I changed pcv valve and since the intake plenum gasket was dirty and oily I changed that out too. Reset the codes. Both are back again.

According to live data on my scanner both upstream 02/AF sensors are reading right around 2.1 volts and both downstream O2 sensors are reading between .1 and .9 volts as the engine runs. From what I understand that's what they are supposed to be reading.
I have no idea why the code is being thrown if the O2 sensor are within range. I'm thinking maybe fuel injectors but Murano's have codes for air mixture that is too rich or also too lean (P0174)

I'm all out at this point... it must be the cats... maybe I got to them too late. I have no idea what else to try at this point smh
2.1 volts is very slightly rich--what are long-term fuel trims (LTFT) for each bank at idle when the engine is warmed up?

Can your scan tool graph live data that you can post (e.g. pic or screenshot etc.)? If so, try a wide-open throttle/decel test while graphing the upstream and downstream O2 sensors. Put the car in low gear and put the pedal to the floor until you exceed 5,000 RPMs and then let your foot off the pedal and coast for a 5-10 seconds. Do one run for each cylinder bank (i.e. graph A/F Bank 1, O2S2 Bank 1 and then A/F Bank 2 + O2S2 Bank 2).

Then, do a separate set of graphs for each bank just cruising at the speed limit while throttling the gas pedal about 1/4 for 3 seconds and let off (decel) for 3 seconds--do this a few times.

The point of all this is to see how the sensors react to varying driving conditions.
 
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One other thing I forgot to add...your scan tool should be able to access mode $06 which is the OBDII non-continuous monitors. These show the various results of tests the ECM funs on the emissions systems and they generally show the minimum and maximum passing values along with the value the ECM actually tested. If you can access this information, there should be tests for catalyst efficiency. The values themselves likely won't makes sense, but you want to see if the tests failed (likely because you have DTCs) and whether the failure was borderline or really badly based on the test value vs. the acceptable range.
 
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Try a bottle of chevron Techron concentrate in your gas tank. 1 oz per gal. ratio.

You can also check for exhaust leak. You can use a leaf blower or shop vac with blower capability and put it on one of your tail pipe and cover the other with plastic or something to seal it. Then turn on the blower and start spraying soapy water on all the joints where a leak may occur.

How many miles do you have? These engines are a also known to burn some oil. That could add to the quicker demise of the CAT.

 

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Discussion Starter · #51 ·
2.1 volts is very slightly rich--what are long-term fuel trims (LTFT) for each bank at idle when the engine is warmed up?

Can your scan tool graph live data that you can post (e.g. pic or screenshot etc.)? If so, try a wide-open throttle/decel test while graphing the upstream and downstream O2 sensors. Put the car in low gear and put the pedal to the floor until you exceed 5,000 RPMs and then let your foot off the pedal and coast for a 5-10 seconds. Do one run for each cylinder bank (i.e. graph A/F Bank 1, O2S2 Bank 1 and then A/F Bank 2 + O2S2 Bank 2).

Then, do a separate set of graphs for each bank just cruising at the speed limit while throttling the gas pedal about 1/4 for 3 seconds and let off (decel) for 3 seconds--do this a few times.

The point of all this is to see how the sensors react to varying driving conditions.
So I start the car up to get the fuel trim, now I have p0430 and p0174 (system too lean bank 2) lol 🤦‍♂️
So P0420 cleared on its own on this start up

Long term fuel trim Bank 1 reads 10.2%
Long term fuel trim bank 2 reads 10.9%

O2 sensor bank 1 sensor 1 reads at 2.2 on average. It fluctuates as low as 2.180 and as high as 2.210
O2 sensor bank 2 sensor 1 reads at 2.30 on average. It fluctuates as low as 2.210 and as high as 2.260

O2 sensor bank 1 sensor 2 reads .650 on average and its not fluctuating much
O2 sensor Bank 2 Sensor 2 reads about .550 on average and its not fluctuating much either

Can't do the throttle test now. But I'll try to do it tomorrow.
I'll also get another reading tomorrow morning from a cold start.
 

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Discussion Starter · #52 ·
Try a bottle of chevron Techron concentrate in your gas tank. 1 oz per gal. ratio.

You can also check for exhaust leak. You can use a leaf blower or shop vac with blower capability and put it on one of your tail pipe and cover the other with plastic or something to seal it. Then turn on the blower and start spraying soapy water on all the joints where a leak may occur.

How many miles do you have? These engines are a also known to burn some oil. That could add to the quicker demise of the CAT.

I'll try the exhaust leak detection this weekend. Car is at about 140k miles. What's techron?? Is that like sea foam??
 

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So I start the car up to get the fuel trim, now I have p0430 and p0174 (system too lean bank 2) lol 🤦‍♂️
So P0420 cleared on its own on this start up

Long term fuel trim Bank 1 reads 10.2%
Long term fuel trim bank 2 reads 10.9%

O2 sensor bank 1 sensor 1 reads at 2.2 on average. It fluctuates as low as 2.180 and as high as 2.210
O2 sensor bank 2 sensor 1 reads at 2.30 on average. It fluctuates as low as 2.210 and as high as 2.260

O2 sensor bank 1 sensor 2 reads .650 on average and its not fluctuating much
O2 sensor Bank 2 Sensor 2 reads about .550 on average and its not fluctuating much either

Can't do the throttle test now. But I'll try to do it tomorrow.
I'll also get another reading tomorrow morning from a cold start.
These are at idle, correct? LTFT is high (lean). What are STFT values for each bank (esp. bank 2)?

What happens to LTFT values when you increase RPMs slowly up to 3,000? Do they drop toward 0? Do they increase?
 

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Discussion Starter · #54 ·
These are at idle, correct? LTFT is high (lean). What are STFT values for each bank (esp. bank 2)?

What happens to LTFT values when you increase RPMs slowly up to 3,000? Do they drop toward 0? Do they increase?
I'll drive it in to work tomorrow and let you know. Maybe air is getting into the system somewhere??
 

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Discussion Starter · #55 ·
These are at idle, correct? LTFT is high (lean). What are STFT values for each bank (esp. bank 2)?

What happens to LTFT values when you increase RPMs slowly up to 3,000? Do they drop toward 0? Do they increase?
Yes the numbers I posted yesterday were at idle. Here are some screencaps of live data from this morning after I drove to work (about 10 miles)
P0174 is now gone lol
P0420 is back and P0430 is still there
I took video for a better look at the live data but I can't upload it until this evening when I'm back home.
53671
53672
53674
53675
53676
 

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Discussion Starter · #56 ·
These are at idle, correct? LTFT is high (lean). What are STFT values for each bank (esp. bank 2)?

What happens to LTFT values when you increase RPMs slowly up to 3,000? Do they drop toward 0? Do they increase?

Here is the live data. Didn't realize father's day was coming up when I said I would post it this weekend.
I haven't rpm tested it yet but I will asap.
 

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It's always better to graph O2 sensor PIDs because then you can visualize what they're doing.

In only a span of about 14 seconds (0:09 to 0:23), the bank 1 downstream sensor switched from lean -> rich-> lean-> rich-> lean-> rich. Pretty much the same for the bank 2 sensor. These values are at idle, correct? If that's the case then that's way too much switching for the downstream sensors. Values downstream should be smooth and relatively steady (usually leaning rich) because the catalytic converters modify the chemistry of the exhaust stream as discussed earlier in this thread. The activity of those sensors is likely why the ECM is throwing those codes. BTW, I believe you replaced all 4 sensors (upstream and downstream), correct? What brand did you use?

Given the high fuel trims, the first thing I would suggest is to verify whether or not you have a vacuum leak. When you get a chance, warm the engine up and then let it idle. Watch LTFT for both banks as you slowly increase RPMs. If they start to drop toward zero the higher the RPMs get then there's a vacuum leak somewhere and you would need to fix that before further diagnosing those converter efficiency DTCs. You'll also want to verify that you don't have any exhaust leaks as nitely suggested previously (esp. since you just had the exhaust apart). Look on YouTube for the ChrisFix video tutorial on that.
 
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Discussion Starter · #58 ·
It's always better to graph O2 sensor PIDs because then you can visualize what they're doing.

In only a span of about 14 seconds (0:09 to 0:23), the bank 1 downstream sensor switched from lean -> rich-> lean-> rich-> lean-> rich. Pretty much the same for the bank 2 sensor. These values are at idle, correct? If that's the case then that's way too much switching for the downstream sensors. Values downstream should be smooth and relatively steady (usually leaning rich) because the catalytic converters modify the chemistry of the exhaust stream as discussed earlier in this thread. The activity of those sensors is likely why the ECM is throwing those codes. BTW, I believe you replaced all 4 sensors (upstream and downstream), correct? What brand did you use?

Given the high fuel trims, the first thing I would suggest is to verify whether or not you have a vacuum leak. When you get a chance, warm the engine up and then let it idle. Watch LTFT for both banks as you slowly increase RPMs. If they start to drop toward zero the higher the RPMs get then there's a vacuum leak somewhere and you would need to fix that before further diagnosing those converter efficiency DTCs. You'll also want to verify that you don't have any exhaust leaks as nitely suggested previously (esp. since you just had the exhaust apart). Look on YouTube for the ChrisFix video tutorial on that.
Ok so I'm looking at live data (scanner doesn't have graphing) and I took a look at STFT and LTFT.
Short term fuel trim is high. Never gets lower than 5.0 on either bank and gets as high as 25.0 on either bank as it fluctuates from what I understand this is way too high.
As for the Long term fuel trim each bank is at around positive 10 at idle (closed loop). When increasing the rpms to about 2500 - 3000 and holding it there, bank 1 drops to negative 9.4 and bank 2 drops to negative 7.0
I've created this change 3 times in a row by increasing the rpm to 2500 - 3000 so it's a solid reading.
So now I'm trying to understand. This is a lean condition correct?? So I'm looking at a vacuum or exhaust leak, or MAF sensor being dirty??

I actually was able to put my leaf blower in my tailpipe and spray soapy water and I didn't find anything on top of the engine or on the joints of the cat catalytic converters.

So the 3 codes I have are
P0174
P0430
P0420

Should I be checking for exhaust leaks now??
 

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This is a lean condition correct?? So I'm looking at a vacuum or exhaust leak, or MAF sensor being dirty??
Likely vacuum leak. A dirty MAF sensor typically causes the opposite reaction to fuel trims (i.e. they get leaner as RPMs increase). Nevertheless, you can still remove the MAF sensor and inspect it.

Should I be checking for exhaust leaks now??
That was what you did with the leaf blower and soapy water and you said that you didn't find anything, correct?
 

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Discussion Starter · #60 ·
Likely vacuum leak. A dirty MAF sensor typically causes the opposite reaction to fuel trims (i.e. they get leaner as RPMs increase). Nevertheless, you can still remove the MAF sensor and inspect it.



That was what you did with the leaf blower and soapy water and you said that you didn't find anything, correct?
Yes, I did do the leaf blower and soapy water but I think I'll try it again. One thing that concerned me is air wasn't blowing out from anywhere tho (I did plug the drivers side exhaust while the leaf blower was blowing thru passenger side exhaust).
So if I did it correctly, wouldn't the air properly escape from somewhere??
 
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