Hey guys. I have a 96 Max SE w/ only 115k on it and it's failing smog on the 0-15mph test in CA. It passes on the 15-25mph part, but is running very lean on the lower part of the test and fails what they call NOX. The guy told me to replace the 02's and the cat and it would definitely pass then. I replaced the 02's first and then had it pre-tested. No change whatsoever. I then replaced the rear cat and still no change. The test shows a very lean condition when the car is running. I've heard that a bad KS can cause this, but I'm not getting an engine light for it and I removed it and did an OHM test on it. I'm not sure if I'm doing the test right though to see if it's good or bad. How exactly do you test them? What else would cause a very lean condition in the motor. Someone told me I may have clogged breather tubes that run in the front and back of the motor as well? Anyone heard of this? Would it possibly be the front 2 cat's that are causing it to run lean? I just don't understand. The car has only 115k on it. What else can I check or replace? Thanks for the help.

daveyg68

 

Are you letting the car get some miles on it before taking it for inspection?

 

Clean your throttle body and the intake runners.
You could have a bad MAF sensor.
Check the resistance of the engine coolant temperature sensor when the car is at operating temperature. It should be approx. 200 ohms when the car is completely warmed up. Run a bottle of Techron fuel injection system cleaner through and drive it hard.

 

Thanks guys. I didn't run it much after installing the cat or 02's. I did hear that you have to run new cat's like 60 miles to really get them heated up. I was going to clean the throttle body and check the EGR tube as well. What are the intake runners? How would I know if the MAF is bad? When checking the resistance on the coolant temp sensor, how exactly are you testing it with the OHM meter? I'll throw the Techron FI cleaner in too.

 

There may well be answers to some of these questons in the stickies, FAQs and on motorvate.ca, however, I suggest you go out and spend $20 (or less) and buy yourself a Haynes manual.

 

Read this thread. http://forums.maxima.org/showthread.php?t=404200

Before spending time checking and cleaning this and that and spending money buying new components, simply have the tech manually open your EGR valve with a vacuum pump. This worked for me as well as other people.

 

CalsonicSE, I did just that today. The tech tested the EGR valve. It was working properly and got vacuum. He then did a pretest and would you believe it passed smog????? He said that he heated up the car so the CAT got super hot before he did the test. I was so psyched. I spent 160.00 to another mechanic that kept testing the car and it wouldn't pass. I take it to a very reputable SMOG shop where they deal with the problems every day and it passes. Lesson: Get the car diagnosed properly from a reputable smog mechanic and don't try to save 20.00 here or there.

BTW, I took off the new CAT and O2 sensors and put the stock ones back on before the test. I was convinced that they were still good and I was right. They tested the 02's and they were working fine, and by heating the CAT up like they did, it was working fine as well.

Thanks for the tips guys and I highly recommend Lafayette Autocare in Lafayette, CA if you need any car work done. Cheers.

 

You should run your car a couple of milesABout 30 miles before doing your smog check. Try changing your filters, spark plugs, fuel system cleaner. Change the easy small things before you spend the big money. If anything get it done ILLegaly.