Hypermiling affecting emissions test

Discussion in 'Emissions' started by SentraSE-R, Jan 15, 2012.

  1. SentraSE-R

    SentraSE-R Pishtaco

    My car failed CA emissions testing last week, and I'm confident my hypermiling had a direct relationship to the problem. When I took it in for the test, I hadn't driven the car in a month, except for a brief drive up the freeway to warm the engine up before the test.

    The failure was due to my clearing the check engine light/malfunction indicator light in October. Since then, I'd driven 800 miles, but some of the drive cycle monitor readiness flags hadn't been set since the MIL clearing.

    My Scion xB regularly triggered the MIL, with trouble codes P0301, P0302, P0303, and P0304, indicating multiple cylinder misfires. But they would all come on as soon as the ignition key was switched on, before the engine was started. I deducted this was because FASing told the OBDII the car was rolling at a speed inconsistent with the (presumed) idle speed timing advance. Once I installed a kill switch, the MIL issues went away.

    Except in October, during a road trip, a connector came loose, disabling my kill switch. I reverted to ignition key FASing, and my MIL came on, with the same P030X TCs. I reconnected my kill switch, cleared the MIL, and drove 800 miles with no issues, until my car failed the functional test, shown above. The smog check tech said a couple of the drive cycle readiness monitor flags hadn't been set since I'd disconnected the battery, or cleared the CEL/MIL. I asked what I needed to do to set the readiness flags, and he recited the common wisdom (you'll see it on the web) that I should drive the car for a week. He'd seen some people needing 2000 miles to set the flags.

    The Scion community saved me a lot of random driving. The catalytic converter driving cycle is 15 minutes at speeds between 60-100 kph, and the O2 sensor driving cycle is >40 mph. The evap emissions leak testing and purge flow monitoring cycles start 5 hours after the ignition is switched off, if the engine coolant temperature has dropped below 35 degrees C.

    I drove 15 minutes one way on the highway, turned around and repeated it, then stopped by the smog testing center. They confirmed the only readiness flag still unset was evap. They suggested I drive 50-60 miles, and it would clear. Instead, I parked my car, confident it would start the evap monitor cycle 5 hours after I turned the key off.

    The next day, I warmed the car up, driving it enough to add 100 miles since the test failure. The car passed smog testing. Examination of the retest shows cleaner emissions after driving the car a distance at speed. Low speed HC results had been 62, only 2 below the maximum allowable level, but dropped to 39 on the retest. Inactivity or the normal way I drive may be raising my emissions, as my HC levels are 3-15X more than average, CO levels are 1-6X the average, and NO levels are 4-7X more than average.

    My other concern is that 800 miles of driving never completed the cat drive cycle. Comments?
    Last edited: Jan 15, 2012
  2. Unleaded

    Unleaded Well-Known Member

    That is strange. My car will be "ready" after only 20 minutes of driving after clearing the CEL. In the summer of 2010 I had a CEL code P0430 (Cat converter) that kept comming on a couple weeks after clearing the code. The day before I had to go for emissions, the CEL came on with the same code. Without the funds to replace the cat converter at the time, I just cleared the code. The next day I went in for the test. I checked the monitors before going, they were all ready. I went in and passed the test. :D
  3. jcp123

    jcp123 Caliente!

    Interesting. I would drive the car some more. Getting the engine and cat warmed up are two big keys to the emissions test. It's conceivable that driving may blow out/burn up some excess buildup in your cat or EGR system. In any case, if your car has an EGR valve, I might remove it and clean it up, then reinstall. I am less familiar with the evap testing, is there perhaps a real fault in the evap system (loose/bad fuel cap, vac lines, etc.)? Maybe you need to find a more "friendly" smog check station (something a lot of people I know may or may not have done when I lived in the Bay Area). Those smog checks are one reason I went to smog-exempt cars out there :D
  4. SentraSE-R

    SentraSE-R Pishtaco

    I set my UG to monitor cat temperature, and took it on a 900 mile roundtrip last week. The cat temperature typically was in the 1100-1185 degree F range while cruising on the freeway.

    My car runs an amazingly low, and emissions-inefficient, 285-550 degree F cat temperature during non-highway P&G. No wonder my HC and NO emissions values were several times the average vehicle's values.
  5. FSUspectra

    FSUspectra Practicing true conservatism!

    Your UG can monitor cat. temps? Was it a listed gauge for your car? I never thought that would be a gauge.
  6. SentraSE-R

    SentraSE-R Pishtaco

  7. FSUspectra

    FSUspectra Practicing true conservatism!

    I'll have to go through mine and see if I can monitor it. Thanks.
  8. SentraSE-R

    SentraSE-R Pishtaco

    Well, thinking this over, I use ~56% of the gas the average xB owner does, but I spew out 3.5-15X the HCs, 3-7X the NOx, and up to 6X the CO of the average xB, when the cat is lit.. If I run the engine 50% as much as the average driver, but spew out 5X the pollution with the cat lit, I'm still polluting the air with 2.5X the pollution of the average.

    Worse, I didn't light the cat significantly for 800 miles. If a cat is 50% efficient, I'm dumping out double the pollution when my cat is unlit. If a cat is 90% efficient, I'm dumping out ten times more pollution when my cat is unlit.

    Logic tells me by saving ~45% on gas, I'm dumping up to 15-75 times the HC, and 15-35 times the NOx, of the average car. P&G is looking like a major loser.
  9. Nevyn

    Nevyn Well-Known Member

    If you insulate the cat to keep it warm for FAS'ing, it'd probably overheat in other conditions. :/
  10. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Do you have any reports from your other vehicles? I know this is the first one for this car (exempt for 5 years), but do you have anything "normal" to compare this to?
  11. herm

    herm Well-Known Member

    How about not stopping the engine?.. let it idle while gliding then pulse. You probably should not P&G near a major city, but out in the country it should be fine.

    The Sonata Hybrid does an automatic P&G on the hwy, shutting off the engine for nearly 1 minute.. somehow they have mastered the catalytic converter problem.

    Most likely there is something wrong with the system.. perhaps a contaminated catalytic converter.. are you using any fuel additives?
    Last edited: Feb 1, 2012
  12. SentraSE-R

    SentraSE-R Pishtaco

    No, I don't have any other emissions tests of my other cars. I did take my car back to the smog test station after my 900 mile RT to SoCal, and its HC levels are back to average, proving there's nothing wrong with my car. They wanted $50 to do the complete test with printout. I opted for a manual test that's not comparable, but it will have to do.
  13. CRT1

    CRT1 Newbie McNewbster

    I read this full thread over at Ecomodder last night with great interest. Sounds like Sentra fouled up his xB pretty bad and needed to burn of a lot of carbon build-up to get the system right again.

    How are other intense FAS P&Gers doing on their emission tests? Sentra's experience is a valid data point, but we must have others out there as well?!

    Here is MA we have required tailpipe tests at the purchase of the vehicle and every year thereafter, regardless of the age of the vehicle. I go in for my year 1 in Sept.

    I am concerned because when I FAS my FIT, when I key-on it runs Open Loop for 2-3 seconds. This is generally when I want to get on the gas for a Pulse. If my pulse only lasts 5 seconds I am spending 40-50% of my time in Open Loop. It is really troublesome to key-on wait for the loop to close and then pulse, but I think that is what I may need to do. Grrrr.
    Last edited: Jul 6, 2012
  14. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    We don't have emissions tests in Texas, except the metro areas of DFW, Houston, Austin, San Antonio. Here in East TX we have marginal air quality, but it's from coal power and manufacturing, not from cars, so they don't test the cars. In other words, I don't know my emissions. I did just replace my cat when the old one developed a crack, so I do care about emissions.
  15. shadescape

    shadescape Banned


    we don't have emission tests in Kansas either
  16. waltermlee

    waltermlee Well-Known Member

    The catalytic converter needs to be heated up to work efficiently. In the first few minutes when a gasoline engine is warming up from a cold start it is emitting its highest level of pollutants/ emissions because the catalytic converter has not warmed up to its optimal temperature. If you are FASing before the catalytic converter can get to its optimal operational temperature or if you are turning off the engine for too long and the temperature of the catalytic converter drops below its optimal range then you might be outputting more smog. The failed emission test may likely be caused by pollutant/residue from previous trips when this has occured. :(

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