car failed inspection

87grandnat

Active Member
Joined
Oct 14, 2003
just had my car inspected and it failed (damn it) the guy said the nox is to highthe standard is 1047 on high speed and miy car had 1316 it also failed low speed the standard is 1146 and my car had 1352, if anyone has any info on what could cause it to fail it would be greatly appreciated, thanks
 
High NOX is usually caused by EGR not functioning. There could be other reasons as well. Your chip may also contribute to the high NOX reading.
 
The EGR valve is on top of the intake manifold on the driver's side. You may have a chip that disables the signal to allow it to work. Could you install a factory chip for the inspection?
 
a lazy O2 sensor may also contribute to high NOx. The EGR is on the drivers side of the intake (has a black round plastic cover over it). With the engine idling, place your finger underneath the valve, against the diaphram and lift the diaphram. At idle, the engine should stumble or die. This tells you the passages are clear. If you have a scan tool, you can watch the EGR duty cycle and the percentages should increase during light to medium acceleration. This tells you the computer is sending a signal to the EGR solenoid. If you disconnect the vacuum hose to the EGR valve and connect it to a vacuum guage and drive it and you should see vacuum on the guage at light to medium throttle. Next, with the help of a friend, start engine place foot on brake and select drive. Then you again rest your finger under the diaphram and lightly throttle up. The diaphram should move up as you throttle up and down as you release the throttle. If all thes these test pass, next look at the O2 sensor and then the cat.
 
yeah i could put the factory chip back in, but i would still like to know the problem for future references. it was kinda funny the guy at the inspection place told me to bring it back on saturday with 60 bucks and hed pass it, so i would do this if i had but would rather do it right
 
Put the factory chip in, turn fuel pressure down, get it good and hot. IF you can talk to the inspector and tell em to put the RPM's up as much as possible on the test. I'm an inspector in Georgia, Nox is usually EGR, cat. converter, and vaccum leak related. I'd check those three.
 
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