hey guys i just failed a smog check: i just replaced the o2 sensor after the cat (used a universal bosch sensor). so this morning i i smog and failed here are my results
[IMG][/IMG]

i have a budget midpipe and greddy sp cat back, warm air intake

any help would be appreciated

thanks

 

NO (ppm) is what failed, you measured 913, max was only 430.

Any codes stored? The o2 after the cat will not have any effect on how the engine runs. It only verifies you catylist is working.

Clean the TB
Replace plugs
Make sure the air filter is clean
Retest

If you fail again, you should look at replacing the front o2's.

 

do that and see what happens?

 

You might want to check your knock sensor

 

how do you check knock sensor?, thanks for the info, im going to change my plugs and replace my air filter, do you think running the budget y pipe is affecting my smog?

 

If your car is properly heated your y-pipe shoud not affect your smog. Do this:

 

ok ill get the plugs and air filter tomorrow and let you know what the results are during the week

thanks

 

Looks like the engine is running lean. You should check for air leak. A few years ago my car had a leak between the throttle body and the air filter box, my NO got to 259.

 

Check your EGR valve functionality...clean the egr pipe. It tends to get clogged up pretty easily with carbon buildup. If you have a stepper motor EGR valve (99s) check the resistance across the pins where you connect the electrical plug. It should measure 22ohms according to the repair manual.
Good luck.

 

The two biggest causes of high NOx readings are:
bad/clogged EGR
bad front O2 sensors

 

KS wont affect it. I just passed emissions with knock sensor and evap codes

 

good info...thanks alot

 

i changed me egr about 8 months ago. went in for a smog yesterday and failed the 15mph NO test. i had 901ppm when max was 675. i passed the two previous years with the old factory egr, one year it was throwing an egr code intermittanly. i just went in for the check when the code wasnt on. passed fine. based on my experience, egr is not the biggest factor. i drove 25 minutes highway speeds in 4th gear to make sure the car was warm before testing.

 

Having a warm engine is good for lowering the HC and CO readings, but bad for NO. Having a cool engine helps lower the NO readings, of course at the expense of raising the HC and CO readings...

 

well guys i finally passed! my 15mph NO reading: 18 25mph:0 i replaced my spark plugs to find they were in good shape, i cleaned my filter, installed my stock y-pipe and passed with flying colors....thanks for all the help