Failed smog

Tiny
TAYLORANDKYLIE
  • MEMBER
  • 1989 PLYMOUTH VOYAGER
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 268,000 MILES
I have a 1989 Plymouth Voyager that has failed it's smog check. On the initial test, it passed all emissions, but failed the pressure test of the EVAP system at.070 with a max of.040. I went through all the lines and found two hoses that were not connected very well, one actually leaked fuel when moved. Thought that this would fix the problem, but when re-tested, it failed again, but at.053 this time. I am having it smoke tested now to locate the leak, but more concerning is the fact that it failed the NOx on the second test. On the first test, the NOx were at 407 with a max of 613, but the HC were 118 with a max of 123. Thinking that if I got the cat hotter, the HC would drop, which it did, all the way down to 91, but the NOx jumped to the 786. Any ideas on what would cause the HC to drop, yet make the NOx jump up so much?
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Monday, February 14th, 2011 AT 11:04 PM

2 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
That catalytic converter may not be functioning properly. Also, have the O2 sensors checked to make sure they are working properly. As far as the leak, most times the only way to find them is with a fog test. So, you're doing the right thing there.
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Wednesday, March 23rd, 2011 AT 6:42 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
PS: Keep in mind, by eliminating vacuum leaks (EVAP) you are running a richer fuel mixture to the engine. Thus, the HC will increase.
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Wednesday, March 23rd, 2011 AT 6:43 PM

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