My 1995 240 has 46,000 miles on a new engine it is an automatic, runs PERFECT."I THOUGHT", here in Texas we have to run the roller dyno at 2 speeds, the engine uses burns no oil, gets excellent mileage, but failed the NOx, it was almost double, there is a code in it, and it states the 3 way catalyst is bad, but there are 2 cats, i am assuming the front is bad since the O2 sensors are before and after the front converter, here is what the car did, HC(ppm) standard132 current 104 pass (high speed)HC (ppm) standard 136 current101 pass (low speed)co% standard .73 current .42 pass (high speed)co% standard .76 current .43 pass (low speed)O2 1.1 (highspeed)O2 1.2 (low speed)
NOx standard 945 current 2118 FAIL (high speed)
NOX standard 1045 current 2181 FAIL (low speed) I know the converter is probably bad , but the HC wasnt that bad, also i pushed up on the egr valve and the engine stumbled at idle, like the passages were clear, when you rev it up in neutrall, it raises up but drops back down, it doesnt stay up all the time it is reved, I put vacuum, on it and it holds the valve up all the way untill let go, please let me know what you think I should do, ...........("front CAT????") thank you in advance for any help Is this vehicle obd-2?, it has the connector and the 2- o2 sensors, but they classify it as not here in Texas, 1996 and newer doesnt have to go on the roller!!!!
Modified by 240sx man at 2:35 PM 11/15/2005
1995 240sx failed the emisson test
-
Magnes
- Posts: 101
- Joined: Thu Jan 30, 2003 6:58 pm
- Car: '89 240SX, done up with a chrome-plated ground wire to the engine.
Re: 1995 240sx failed the emisson test (240sx man)
It sounds like it is OBDII, but there are some cars with the OBDII connector, and dual O2 sensors that are not fully OBDII compliant, so I'm not sure.
You only have 1 catalytic converter. The thing ahead of the rear axle is a pre-muffler. Your EGR is behaving normally, change the cat.
You only have 1 catalytic converter. The thing ahead of the rear axle is a pre-muffler. Your EGR is behaving normally, change the cat.
Re: 1995 240sx failed the emisson test (Magnes)
Thanks for the reply, the car has an exhaust manifold,then an O2 sensor, a cat on the down pipe, an O2 sensor, then another cat, then a resonator, then the muffler at the back. here is a page with them both on it
http://rep.racepages.com/parts...e#top
http://rep.racepages.com/parts...e#top
-
Magnes
- Posts: 101
- Joined: Thu Jan 30, 2003 6:58 pm
- Car: '89 240SX, done up with a chrome-plated ground wire to the engine.
Re: 1995 240sx failed the emisson test (240sx man)
Hmm, 2 cats, only one of them is monitored. That's news to me.
What I can say is that a cat needs O2 sensors upstream and downstream for it's performance to be monitored. If you are getting a "bad cat" code then it has to be the upstream cat according to your description of the O2 sensor locations.
What I can say is that a cat needs O2 sensors upstream and downstream for it's performance to be monitored. If you are getting a "bad cat" code then it has to be the upstream cat according to your description of the O2 sensor locations.
Ok I need your CO2 readings to to enter into a table to calculate if you are dealing with more then a bad cat. I think you are based strictly on your NOX readings. Your oxygen content is high which does suggest the cat is very weak.
Now let me clarify something with nissan systems and OBDII in general. IF any of you take a very close look at nissans total car line up in 1994 then look at the line up in 1995 almost all nissan models changed design from 94 to 95. Every model that changed The sentra went from B13 to b14, the 240 went from s13 to s14, the max went from j30 to A32. The altima was still new so its change held till 97. In any case all the cars that got model changes got newly designed engine control systems. These new systems contained OBDII charicteristics and did have OBDII connectors. THough the systems were not fully OBDII compliant some aspects were missing [most evap moniters were not installed]
So in your case you have the OBDII cat moniter but your car is not technically OBDII. Federally manidated OBDII standards have 2 very important requirements that car manufacturers must have on the cars. 1)the emissions system must be able to moniter and test its components to determine if they are functional.If not A check engine light must be set if they fail the test. During debate between government and the manufacturers the agreement the light doesnt have to come on until the second failure during moniter/test. So if theres a hickup the light wont unneccesarily send people to the dealer for repairs. 2) The systems must have a connection that is universal on all vehicles for scan tool diagnostics on a generic scan tool.
Nissan continued to use their own scan tool [Consult/consultII] connection point as well as having the generic connection point from 96 till 2000 when they finally converted all consult communications to the OBDII connector.
Your oxygen readings are slightly high for the table. That oxygen reading suggests you might be getting air in the exhuast some where [an exhaust leak]. This also could suggest why your NOx are high. If their is even a small hole in your exhuast somewhere it will reduce the back pressure enough to not allow the EGR to open and hold. You can not acuratly test the EGR function at a stand still since there isnt enough back pressure even with perfect exhuast pipeing. The car would need to be underload and a vaccum gauge tee'd into the egr vaccum line between the BPT and EGR. If it gets vaccum under cruise or steady lite throttle and holds it shows vaccum will be supplied to the egr when needed. You then prove the egr will open and hold vaccum with a manual vaccum pump which you did. Rpm dropped more then 100rpm which suggests it has enough flow. When vaccum testoing the egr you only apply the vaccum the gauge showed when you drove it as that is all it will see. If you have the same results with that vaccum then the egr can and will work. I will say if your supply vaccum to the egr under driving conditions is around 3hg of vaccum the egr is not going to work well enough. The reason that vaccum isnt available to the egr is likely because the BPT is not closeing the vent to ship the vaccum to the valve. This would be the result of having a small exhaust leak.
Alot to read I know but you can say your now well informed right....lol
Now let me clarify something with nissan systems and OBDII in general. IF any of you take a very close look at nissans total car line up in 1994 then look at the line up in 1995 almost all nissan models changed design from 94 to 95. Every model that changed The sentra went from B13 to b14, the 240 went from s13 to s14, the max went from j30 to A32. The altima was still new so its change held till 97. In any case all the cars that got model changes got newly designed engine control systems. These new systems contained OBDII charicteristics and did have OBDII connectors. THough the systems were not fully OBDII compliant some aspects were missing [most evap moniters were not installed]
So in your case you have the OBDII cat moniter but your car is not technically OBDII. Federally manidated OBDII standards have 2 very important requirements that car manufacturers must have on the cars. 1)the emissions system must be able to moniter and test its components to determine if they are functional.If not A check engine light must be set if they fail the test. During debate between government and the manufacturers the agreement the light doesnt have to come on until the second failure during moniter/test. So if theres a hickup the light wont unneccesarily send people to the dealer for repairs. 2) The systems must have a connection that is universal on all vehicles for scan tool diagnostics on a generic scan tool.
Nissan continued to use their own scan tool [Consult/consultII] connection point as well as having the generic connection point from 96 till 2000 when they finally converted all consult communications to the OBDII connector.
Your oxygen readings are slightly high for the table. That oxygen reading suggests you might be getting air in the exhuast some where [an exhaust leak]. This also could suggest why your NOx are high. If their is even a small hole in your exhuast somewhere it will reduce the back pressure enough to not allow the EGR to open and hold. You can not acuratly test the EGR function at a stand still since there isnt enough back pressure even with perfect exhuast pipeing. The car would need to be underload and a vaccum gauge tee'd into the egr vaccum line between the BPT and EGR. If it gets vaccum under cruise or steady lite throttle and holds it shows vaccum will be supplied to the egr when needed. You then prove the egr will open and hold vaccum with a manual vaccum pump which you did. Rpm dropped more then 100rpm which suggests it has enough flow. When vaccum testoing the egr you only apply the vaccum the gauge showed when you drove it as that is all it will see. If you have the same results with that vaccum then the egr can and will work. I will say if your supply vaccum to the egr under driving conditions is around 3hg of vaccum the egr is not going to work well enough. The reason that vaccum isnt available to the egr is likely because the BPT is not closeing the vent to ship the vaccum to the valve. This would be the result of having a small exhaust leak.
Alot to read I know but you can say your now well informed right....lol
Oh an additional note here on the 2 cats. Yes some had 2 cats and some had only one. It didnt matter where the cars were sold or anything. I think it had something to do with how the car emitted in factory testing. Any how the second cat after the second O2 is simply a clean up cat [oxidizing cat] You can not tell by looking at the exhuast weather it is a cat or not. It may just be the shell of a cat and be empty inside. They use it either way. Only way to tell is look inside of it. IF it is a cat it does not need to be moniters as it does not do the bulk of the clean up.
WOW!!!!! that was a great response, here is my CO readings high speed 14.3---low speed 14.3 exactly the same, O2-high speed 1.1, low speed 1.2 , of course all the things related to this car wernt disclosed,are they ever???, my son told me that on the first engine the first cat on the downpipe, turned completly red ,burning the floor pan rubber, that is on the underlay of the carpet, the cause was my son washing the engine and not telling me it was bucking and missing for 2 days he was away at school, water had gotten down to the plugs in the head shorting out against the tube for the plugs, he just now told me that....sorry.......there is also an exhaust leak at the front of the rear cat , enough to hear and feel slightly........I am going to put on some new cats and try again, thank you for taking the time to help........
Re: (NISTECH)
PASSED!!!!!....man that took a while, from ordering the cats from california to ,not getting the right exhaust gaskets ,to the flange on the down pipe, not being welded in the right spot, causing the gasket to not be able to stay on,if i had not needed to get this thing inspected before 15 days were up , I would have sent the down pipe back for another one,ended up being ,first cat almost gone completly, just a small amount left, the rear cat completly blown through, ok so here are the numbers .... down pipe cat installed, under seat cat installed, new plugs , and premimum fuel in 3 seperate tank fulls...........
HIGH SPEED LOW SPEEDHC - STD. 132 - CURRENT.20 STD. 136-CURRENT- 36CO% .73 .03 .76 .06CO2 15.0 15.1O2 0.0 0.0NOx 945 353 1045 753DILUTION >6 15.0 >6 15.2
The cats did the trick as well as ,making sure the exhaust leaks were fixed, thanks again NISTECH..........I really think it could have been better since the cats were hot and ready, we had a 40 degree day and it sat for over 3 hours waiting for the retest, they got to make that money.......also they tried to run the front of the car up on the dyno, it is the kind that just sits on the floor and sticks up,about a foot, I had to run out and tell him it was a rear wheel drive.he then asked ."ARE YOU SURE????"......I told him," if he wants to check ,look for the large pipe that goes back to the rear end under the car.".................
HIGH SPEED LOW SPEEDHC - STD. 132 - CURRENT.20 STD. 136-CURRENT- 36CO% .73 .03 .76 .06CO2 15.0 15.1O2 0.0 0.0NOx 945 353 1045 753DILUTION >6 15.0 >6 15.2
The cats did the trick as well as ,making sure the exhaust leaks were fixed, thanks again NISTECH..........I really think it could have been better since the cats were hot and ready, we had a 40 degree day and it sat for over 3 hours waiting for the retest, they got to make that money.......also they tried to run the front of the car up on the dyno, it is the kind that just sits on the floor and sticks up,about a foot, I had to run out and tell him it was a rear wheel drive.he then asked ."ARE YOU SURE????"......I told him," if he wants to check ,look for the large pipe that goes back to the rear end under the car.".................