I have a 1993 nissan altima gxe - 2.4 ltr engine with 85,000 and have been having problem passing the nox emmisson part of my inspection. I have changed the egr valve, vaccum solonoid switch, bpt valve, oxygen sensor and all of the vaccum hoses. Everytime I fail the shop keeps saying its my catalytic converter (its only two years old), my question is how can you tell if I have a 2-way converter or a 3-way converter because its my understanding is that if its 2-ways it only takes care of HC's and the CO" s which it passes. What would you recommend?
The EGR passages could be plugged with carbon. Manually pull on the EGR valve at idle, car should come very close to stalling, if not actually stalling. If littel or no change is seen then the passages must be cleaned out.
July, 3, 2007 AT 5:39 PM
I did test the egr valvle at idle and engine stalled. I am starting to think I have a defective catalytic converter even though its two years old. I even put in BlueSky (6oz) twice ran the gas down to practically empty followed all the directions and still failed (the readings did come down a bit from 3.23 to 2.89 and the limiit is 250 this is why I and now thinking the converter is somehow defective. Have you ever heard of such a problem with a converter?
July, 4, 2007 AT 7:29 AM
Yes, but it isnt real common. If you have a vacuum tester, hook a long piece of vacuum line to it and use the tester in place of the EGR valve and drive it with the tester where you can see it. This will tell you if the system that controls it is applying vacuum to the valve when driving
July, 10, 2007 AT 2:02 PM
I performed the test you suggested, by teeing in a vaccum gauge between the bpt and the egr valve. I am getting 3 inches of vaccum at the egr valve on accelleration with the rpm at 2000 to 2500 rmps. When I deaccelerate the vaccum falls off and turns back on when I accelerate. I would like to know if I should take a chance and retest, this would be my fourth time at $29.00 a pop. I am still leary of the converter. I ran this test for 26 miles and it was consistant. I also contacted the manufacturer of the converter and explained the problem. He concurred with me that is possible that the converter could be bad and is covered under warranty. What do you think should I get the new converter then retest?
July, 11, 2007 AT 7:24 AM
If it is free, go for it. Not sure 3 inches of vacuum is enough to activate the egr valve.
July, 11, 2007 AT 9:35 AM
Would the converter cause me to get low vaccum as you suggest? According to all the manuals (Haynes - Shop Manual for 1993 manual) they said 3 inches was enough what should it be - because I'm going for the converter and I going to try your test again.