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  1. #1
    FEP Super Member cb84capri's Avatar
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    Exclamation emissions gurus needed...

    I recently picked up a 98 dakota 3.9 2wd. Anyways, I am having trouble getting this truck to pass emissions. I have tried 3 times now. Here's a rundown of what is going on.

    First test:
    I brought it to the testing facility hot. The results indicated a bad cat, failed hc, co, and nox at 40km/h roll miserably. Passed idle though.

    Results:
    40km/h

    HC ppm Limit 55 Reading 96 Result:Fail
    CO% Limit .31 Reading .80 Result:Fail
    NO ppm Limit 612 Reading 2906 Result:Fail
    Dilution 14.34

    Idle

    HC ppm Limit 150 Reading 107 Result:Pass
    CO% Limit .7 Reading .65 Result:Pass
    Dilution 13.99

    Second test:
    I found my original cat was hollow! I cut it off and installed a new 3 way cat. Truck passed idle, and hc and co at 40km/h roll, but failed nox while rolling. Brought truck in hot.

    Results:
    40km/h

    HC ppm Limit 55 Reading 22 Result:Pass
    CO% Limit .31 Reading .00 Result:Pass
    NO ppm Limit 612 Reading 1229 Result:Fail
    Dilution 14.60

    Idle

    HC ppm Limit 150 Reading 18 Result:Pass
    CO% Limit .7 Reading .00 Result:Pass
    Dilution 14.30

    Third test:
    In my attempt to get cooler combustion temps, I switched out to the autolite plugs equivalent to rc9lc's gapped .040", installed a 180* t-stat and flushed and refilled the cooling system. Brought truck in hot.
    Failed nox a little worse than test 2. What gives?

    Results:
    40km/h

    HC ppm Limit 55 Reading 19 Result:Pass
    CO% Limit .31 Reading .00 Result:Pass
    NO ppm Limit 612 Reading 1271 Result:Fail
    Dilution 14.40

    Idle

    HC ppm Limit 150 Reading 11 Result:Pass
    CO% Limit .7 Reading .00 Result:Pass
    Dilution 14.10

    So my conclusion is the truck is running lean, I want to try and check for vacuum leaks tomorrow again, but I haven't found any so far. How do I richen it up? The oil is new. Is there some way to rig up an egr system? Can timing be retarded? This truck has a distributor. The pcv valve seems to be cycling just fine. I need to get this truck on the road and my capri put away. I really need some help on this one.

    cale
    Last edited by cb84capri; 11-16-2010 at 01:00 AM.

  2. #2

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    I'm not an expert but have dealt with California emissions too much.

    Timing is very important. The O2 sensors can cause a lean or rich mixture. They can be tested but you need a book. Lean can certainly be caused by a vacuum leak but on a 98 Dakota there shouldn't be very many vacuum leak areas. One area of concern is the air intake. It must not leak or the Mass Air Flow sensor can read wrong. No cracks or holes or loose clamps on the ducting.

    I'm not familiar with the 3.9 Dodge V6 but I'm surprised there is no EGR. That's the one thing that will reduce NO but Chrysler may have dealt with it another way.

    Check codes. They could tell you a story of what's going on but not necessarily what to fix. Service manuals are a must when dealing with emissions. Haynes and Chilton may not tell you much but may describe how to test each item.

    If I remember right timing that is too far advanced will result in high NO. Too retarded will increase the HC. It looks like with the new Cat that the HC is under control. Since timing is the easiest to deal with definately check that first.
    1986 Tbird 3.8
    1992 Ford TBird LX 3.8
    1992 Ranger XLT 2.3

  3. #3
    FEP Super Member cb84capri's Avatar
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    thank you for your response, tbirdsps!

    the check engine light is not on, and there are no codes. i hooked up my code reader to it and found nothing. and you are right there are not many vacuum lines.

    from memory, the only vacuum devices are:
    -power brakes
    -hvac vacuum line t'd off power brake vacuum hose
    -evap purge valve
    -pcv valve

    this truck does not have a maf sensor. it must be speed density. i think the only way chrysler dealt with nox emissions was through the use of a 3 way catalyst.

    i am unsure as to whether i can just turn the distributor to retard the timing on this. normally i would try this and not think twice but i saw somewhere something mentioned about there being some goofy procedure to this (more than just unplugging the coolant temperature sensor).

    this is the cat i bought:
    http://www.jegs.com/i/Dynomax/289/15...oductId=744730

    could this be the culprit?

    and i forgot to put this but i ran a can of sea foam through the pcv with the old cat still on the truck.

    thanks,
    cale

  4. #4

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    Being a 98 I'm surpised that you have no codes. The OBDII system is designed to report misfire, lean, rich etc. It sure sound like you said...lean.

    You need a book to adjust the timing or someone who has one to instruct you. My experience is all Ford and we have to disconnect the SPOUT in order to adjust timing. My newest Ford is 1992. In general the computer won't let you change the base timing on a Ford unless the SPOUT is disconnected.

    How about a google search on the Dodge for timing instructions.
    1986 Tbird 3.8
    1992 Ford TBird LX 3.8
    1992 Ranger XLT 2.3

  5. #5
    FEP Super Member cb84capri's Avatar
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    Quote Originally Posted by tbirdsps View Post
    Being a 98 I'm surpised that you have no codes. The OBDII system is designed to report misfire, lean, rich etc. It sure sound like you said...lean.

    You need a book to adjust the timing or someone who has one to instruct you. My experience is all Ford and we have to disconnect the SPOUT in order to adjust timing. My newest Ford is 1992. In general the computer won't let you change the base timing on a Ford unless the SPOUT is disconnected.

    How about a google search on the Dodge for timing instructions.
    from what i found doing a search, timing is not adjustable on the magnum engines. the distributor drives the cam sensor and this controls the injectors. this could be entirely wrong, hopefully i can get on all data tomorrow and find some concrete answers.

    cale

  6. #6
    FEP Power Member 4eyegt's Avatar
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    Can you get a DRB and hook it up? Chrysler will allow a +/- 10 on the long term and short term fuel trims and still be normal if i remember correctly. I swapped to stand alone on my 98 Dodge since I have no smog. Mine is speed density from the factory.

    I've never tried this but I heard with brand new cats you can run isopropal alcohol in the tank to reduce Nox for testing purposes.

    Best bet is to get the DRB, which is Chryler scan tool, and hook it up to see what is going on.

  7. #7
    FEP Super Member cb84capri's Avatar
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    tomorrow i am hooking up a snap on scan tool to see some live data. i'm going to run it on an exhaust gas analyzer too. i just put 5 gallons of 93 octane in it to see what happens, since i had it laying around.

    i'll research more on the isopropal alcohol, thanks! i've got a couple other tricks up my sleeve as well as a last resort.

    cale

  8. #8
    FEP Power Member Durango's Avatar
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    Edit: Didn't notice this thread is 2 months old - any updates?

    That is totally the *wrong* converter. There's a reason the cat you bought is $90 and the correct one over is twice that. All cats are not the same - part of the reason why you cannot stick these generic "football" cats on an OBD-II vehicle in the state of California. You must install the correct converter for the vehicle.

    The converter that belongs on there has a different catalyst makeup than the correct one does. A properly functioning OBD-II vehicle does not need to be "brought in hot" to pass smog. If it's up to normal operating temp, that's fine.

    The timing on this is computer controlled. You shouldn't be messing with the distributor. You can check the base timing to make sure it is where it belongs, but leave it alone. I am not positive on the V6, but you may have no effect even if you loosen and move the dist - the computer may compensate for that.

    Have you checked the oxygen sensors to make sure they are switching properly?
    1981 Durango (ends my 18 year drought of not owning a F/Z)

  9. #9
    FEP Super Member cb84capri's Avatar
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    just saw this response. ya i figured it out. magnaflow heavy metal cat solved all my nox problems, and i got it for less than the price i paid for the walker. it passed with flying colors. i got a full refund on that walker piece of crap too.

    i checked the o2s and they were switching just fine on the scanner. that was when i determined the new cat was junk.

    oh and there is no way of adjusting the timing mechanically on this truck.

    cale
    Last edited by cb84capri; 02-03-2011 at 10:46 PM.

  10. #10

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    Quote Originally Posted by cb84capri View Post
    just saw this response. ya i figured it out. magnaflow heavy metal cat solved all my nox problems, and i got it for less than the price i paid for the walker. it passed with flying colors.
    I'll give it a try. Magnaflow vs. nox analyzer round 1! Wish me luck.

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