Failed CA Smog 3.0 N0x very high

[Konman]

I just bought an 88 T4R with a 95 3.0 at least that is what i was told. The truck currently has 4.10's with 32x11.5x15, its a dog...will be getting 4.88's later this week. The previous owner also installed a 2.5" pipe half way after the CAT and welded a flowmaster 1 hamber on it.


I just signed on today but have owned a couple of Yotas previously (84 semi bulit mini-truck and just sold a bulit 88 FJ62). I have worked on a lot of LC's (2F,3FE).



So here is the deal. Iike an idiot i didnt check the truck over before heading down to get a smog.


Timing was at 25 BTDC during the test. Here are the numbers


%CO %O2
Test RPM MEAS MEAS
15 MPH 1555 13.1 2.7
25 MPH 1690 13.6 2



HC
Test RPM MAX GP MEAS
15 MPH 1555 84 308 56
25 MPH 1690 70 258 39




CO%
Test RPM MAX GP MEAS
15 MPH 1555 0.49 2 0.28
25 MPH 1690 0.63 2.2 0.22



Nox (PPM)
Test RPM MAX GP MEAS
15 MPH 1555 1006 1788 1952
25 MPH 1690 866 1588 2000


As you see I passed everything but NOx. I think the machine only goes to 2000.


The smog tech told me to change the CAT and check the EGR system and fix the timing.



I went home and changed the oil and was driving to a friends house to look over the truck when the MIL came on. It threw code 71 EGR. I checked the EGR per the manual and checked the whole system with the exception of the VSV. I will check that in the next day or so. I found that my EGR vacuum mudulaor had a blocked filter and was all wet. I changed it with one from a LC that very close part numbers. I restested the modulator and it passed all the vacuum reading tests per the manual. I set the timing to 10 BTDC and cleared the MIL. No more MIL. I also changed the CAT yesterday as the previous owner was paying for it.


I went for a retest today and would have failed if the tech didn't stop the test. I am going to test the large metal pipe from the EGR as they tend to gum up in the LC's all the time.

I have also read her about O2 sensor, spark plugs and filter. I don't want to just change parts.


Any help would be greatly appreciated.

 

[Froglips]

Since all your emissions are okay except NOx, I would suspect the O2 sensor. On other combustion sources such as boilers, reducing combustion air is one way to reduce NOx (a lot of nitrogen is brought in with the air). If the O2 sensor is fouled, it keeps asking for more air. With the CO being as low as your numbers are, it is obvious that you are getting plenty of air, possibly too much. Of some curiosity however is that I only had one vehicle that I have had to replace the O2 sensor on and it gave me a Check Engine Code that I could look up.

 

[MikesToy]

Don't they have pass or don't pay shops anymore in CA?

 

[Konman]

Yes, the tech stopped the test so that the results are not provided to the State. If you fail 3 times in a row, you may have to go see the referee. I going to try Seafoam and check oscillations for the O2 sensors.

 

[MikesToy]

I used to live in CA and passed every smog test.