Nissan Repair: Not passing 15mpg 1800rpm test NO to high, fuel pressure regulator, hello room

Question
QUESTION: Hello Room,
I am having a problem with No PPM on the slow speed test.
Here my test as of 3/13/07 7:00PM.
Speed PRM  %CO2  %O2   HC   CO %  NO
15    1833 13.99 0.69  99  .55    2149
25    2807 13.82 0.77  89  .66    715

Here is what i have done so far. Checked the operation of the EGR valve, replaced muffler, Cat is only had 15,000 miles on it. Replaced Exhaust pipes from Exhaust manifold
to tail pipe.   Replaced missing bolt's to exhaust manifold.  Removed EGR and checked ports.

EGR does kill engine if you use a small hand vac hooked to it.

Anyone help with this problem.
Thank you,
Leroy

ANSWER: Leroy,

A stuck injector will cause the problem at the lower RPM range.  Check the pressure on the injectors and see if you are within range.  Also, a broken fuel pressure regulator will do it too.  You mileage will drop and it will run fine but the car will fail test.  Check the pressure and after you cut the engine off see if the pressure drops instantly.  If so you have a defective injector.  Lastly, the fuel filter can cause the problem too.

---------- FOLLOW-UP ----------

QUESTION: Hello Von Sudderth,
First let me say thank your for help. Here's what i did from your input. I tested the Fuel pump holding at 36 psi no problem. Held pressure after sutting truck off for about 5 mins or more. Also tested the fuel pressure after the fuel filter. Then very slowly drop off.  Found a EGR vacume line leak fixed that when and retested and got this.
Speed PRM  %CO2  %O2   HC   CO %  NO
15    1833 13.99 0.72  107  .55    2341
25    2807 13.82 0.77  101  .66    889

Really no change,  What would you do now? Vaume leak in the intake manafold? TBI unit?  

I really want me 4x4 back on the road. Anymore help you can give would be great.

Thank you,
leroy

ANSWER: Leroy,

The fuel system seems to be in order as does the EGR.  So, check the distributor for oil on the optics and make sure the plugs are in good order.  The timing has to be on exact for the system to pass smog.  You can advance it a couple of degrees after the fact.  But, for the test the timing needs to be spot on.

---------- FOLLOW-UP ----------

QUESTION: Von,

I replaced all 8 of the plugs. Checked the timing and she is at 9.2 BTC Factory says 10 BTC idle changes from 800 to 850 back and forth.

Anything else to check Von?
THank you
Leroy

Answer
Sounds like the minimum air needs to be set for idle.  Also, you probably have a vacuum leak and the computer is freaking out due to this.  Lastly, check and replace the throttle position sensor if it is out of range.  Getting the thing to respond to throttle response is important to getting past the SMOG test.