High NOx after replacing gas cap

Tiny
MAYNARDGK
  • MEMBER
  • 1999 OLDSMOBILE INTRIGUE
  • 3.5L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 130,000 MILES
I went to smog test car down the road, it passed emissions but needed gas cap.
I drove to store and got new gas cap and returned directly to testing: Big fail!

1st test: 2nd test: Max:
HC NOx HC NOx HC NOx
24 291 <- 15 mph -> 17 873 51 419
23 422 <- 25 mph -> 19 596 35 706

There was no tampering with engine in between the tests. What component could
be producing such results, how could the fuel vapors change the behavior?
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Thursday, October 1st, 2015 AT 8:58 PM

1 Reply

Tiny
HMAC300
  • EXPERT
It may have got to much fuel and engine wasn't warmed up. Change oil and filter, drive about 20 miles down eway if you can to get good and warm then get it tested. If engine light comes on then have that checked for codes. It may be the canister prge didn't get enough time to work properly
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Friday, October 2nd, 2015 AT 7:11 AM

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