87 5th Avenue Emission Problems

Discussion in 'General Motoring' started by Mr. Minnow, May 28, 2005.

  1. Mr. Minnow

    Mr. Minnow Guest

    I took my car(87 5th Ave with a 318(5.2L) v8) in for an emission test and it
    failed miserably

    Here are the results:

    ASM2525 Test
    Curb Idle Test

    Limit Reading Result
    Limit Reading Result
    HC ppm 83 197 FAIL 300
    504 FAIL
    CO% 0.46 0.16 PASS 1.50
    6.76 FAIL
    NO ppm 893 1220 FAIL N/A
    N/A N/A
    RPM 1092 VALID RPM
    854 VALID
    Dilution 13.8 VALID
    Dilution 17.2 VALID

    What are the possible causes and cures? TIA

    P.S. It passed the Gas Cap Pressure Test and Fuel Filler Integrity Check
    Mr. Minnow, May 28, 2005
  2. Mr. Minnow

    Mr. Minnow Guest

    Sorry about that here's a better version of the report

    ASM2525 TEST

    HC ppm 83 197 FAIL
    CO% 0.46 0.16 PASS
    NO ppm 893 1220 FAIL
    RPM 1092 VALID


    HC ppm 300 504 FAIL
    CO% 1.50 6.76 FAIL
    NO ppm N/A N/A N/A
    RPM 854 VALID
    Mr. Minnow, May 28, 2005
  3. It's *very* hard to read your results -- the tabulation didn't come out as
    you tried to make it do -- but it looks to me as if your results are:

    HC: 197ppm (limit 83ppm, FAIL)
    CO: 0.16% (limit 0.46%, PASS)
    NOx: 1220ppm (limit 893ppm, FAIL)

    Your CO is about 1/3 of the allowable limit, and is an excellent reading
    for a carbureted car -- but your HCs are more than double the allowed
    limit, and your NOx is 1/3 higher than allowed. This combination of
    results suggests your engine is running so lean that it is misfiring.
    Those cylinders that do fire produce a great deal of NOx due to the lean
    mixture, while those that do not fire produce a great deal of HC due to

    (These '85-'89 civilian M-body cars with the Holley 2bbl don't generally
    run very well in stock form, even when everything is set by the book. Lean
    surge under steady throttle is the rule, rather than the exception. Not
    that this helps you -- just saying.)

    So, what's causing your misfiring? Could be any number of things. A faulty
    Oxygen sensor in the driver side exhaust manifold (how long since you
    replaced it?). A faulty carburetor, a faulty Lean Burn computer, a plugged
    fuel filter...it might not even be a lean misfire at all; your readings
    could also be caused by the reduction portion of the exhaust catalyst
    system having reached the end of its life, resulting in very high NOx
    tailpipe readings and insufficient free Oxygen in the exhaust stream to
    allow the oxidation section of the catalyst to clean up the HC.

    Time for some systematic diagnosis by someone who has considerable
    experience with the carbureted Mopars of the mid '70s through late '80s.
    Just throwing parts at it will get very expensive long before the problem
    is solved.

    Daniel J. Stern, May 28, 2005
  4. Mr. Minnow

    aarcuda69062 Guest

    Running lean with a possible inoperative EGR and non functioning
    catalytic convertor.
    Way too rich.
    aarcuda69062, May 28, 2005
  5. Mr. Minnow

    Comboverfish Guest

    Dan, I haven't seen the whole original post; are these readings at
    idle? The limits seem rather strict for a 1987 vehicle. What state is
    this guy in?
    I would say that a lean burn 318 that met these failure limits is a
    decent running engine. That doesn't help the car owner, but it sounds
    like his state is trying to get rid of carbureted cars in one swoop...
    Lean misfire (very minor) is my immediate guess. I'm sceptical that
    the converter has failed to reduce NOx while still oxidizing CO like a
    champ. I mean, if his typical engine is producing typical CO, this
    converter is doing quite a job to get it down to .16%.
    Hear, hear! Some research in his yellow pages for a shop that doesn't
    wince when he mentions his problem would be a good start.

    Toyota MDT in MO
    Comboverfish, May 28, 2005
  6. Mr. Minnow

    Mike Romain Guest

    Away we go again. Dan, why do you suddenly cross post this BS without
    giving us the full post you are replying to?

    It makes you seem like a total ass and yet you do it all the time.

    The last couple times folks have asked for clarification, you have
    ignored it.

    86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
    88 Cherokee 235 BFG AT's
    Mike Romain, May 28, 2005
  7. Mr. Minnow

    Guest Guest

    Is this vehicle still 100% stock, or has somebody screwed around with
    the lean-burn?I've seen these engines "converted" to standard carbs
    (remove the lean-burn) not have a chance of passing E-Test

    Otherwise,Mr Stern has pretty well covered it.
    Guest, May 28, 2005
  8. This is the "Acceleration Simulation Mode" test, IOW a test under load.

    <snip another difficult-to-read report>

    Next time, type it up like this:

    HC: 197ppm (limit 83ppm) FAIL
    CO: 0.16% (limit 0.46%) PASS
    NO: 1220ppm (limit 893ppm) FAIL
    <snip> retyped:

    HC: 504ppm (limit 300ppm) FAIL
    CO: 6.76% (limit 1.5%) FAIL
    NO: N/A

    Still looks like lean misfire under load, possibly inoperative or clogged
    EGR system, possibly dead catalytic converter(s), possibly inoperative
    Oxygen sensor, possibly malfunctioning carburetor, possibly malfunctioning
    Lean Burn computer...

    ....answer's still the same: Proper and skillful diagnosis.

    Daniel J. Stern, May 28, 2005
  9. Those are ASM2525 (acceleration simulation).
    Oh, I donno...I had a '65 car that would reliably pass emission
    tests with similar limits. The guy's idle results and limits are

    HC: 504ppm (limit 300ppm) FAIL
    CO: 6.76% (limit 1.5%) FAIL

    Those are pretty standard state limits for an '87 car, and he's flunking
    them very, very badly.
    If he's running lean enough to cause those readings, there won't be much
    CO off the manifold in the first place, so the catcon won't have a big job
    getting rid of it.
    He might be on the phone awhile. There weren't all that many techs who
    could do a good job with these Lean Burn systems when they were current
    and new!

    Daniel J. Stern, May 28, 2005
  10. I included all the pertinent info supplied in the original post. When more
    info was posted in the original group, I supplied that, too.

    If you don't like my posts, don't read them -- problem solved.

    Daniel J. Stern, May 28, 2005
  11. Mr. Minnow

    aarcuda69062 Guest

    Lean misfire with 6.7% CO and attendant 504 ppm HC?

    I don't think so...
    Yup, the rest of the gas readings would be a big help also.
    aarcuda69062, May 28, 2005
  12. Mr. Minnow

    Comboverfish Guest

    OK, the limits seemed pretty tight for an idle test - that explains

    No doubt. I'd go after rich-running culprits first; gross causes like
    air bleed blockage in the carb, choke closed, etc...

    The converter may be toast already having to deal with this kind of
    overload (at idle).
    That's a challenge I like, but the work would be "by the hour" for

    Toyota MDT in MO
    Comboverfish, May 28, 2005
  13. Lean misfire *under load*. The 6.7% CO and 504ppm HC are idle readings.
    Daniel J. Stern, May 28, 2005
  14. Air bleed, perhaps, but a stuck-closed choke doesn't jive with 0.16% CO
    and 1220ppm NOx under load.
    Very possibly so. I can't remember if they were still farting around with
    multiple converters in '87.
    Well, that's part of the challenge: matching a tech able *and* willing to
    put in the time with an owner able *and* willing to pay him to do so!
    Daniel J. Stern, May 28, 2005
  15. Mr. Minnow

    aarcuda69062 Guest

    True enough... your text reply followed the idle reading though.
    aarcuda69062, May 28, 2005
  16. Mr. Minnow

    Comboverfish Guest

    That's the problem here... there are surely multiple problems which
    will all need to be corrected before all three gasses are within the
    allowable limits.

    We're theory pissing without hands-on testing. Great, now I just typed
    'pissing' and 'hands-on' in the same sentence.

    Toyota MDT in MO
    Comboverfish, May 28, 2005
  17. Mr. Minnow

    Mr. Minnow Guest

    I'm From Canada (ONT.) And I forgot to mention a stubborn oil leak from your
    guess is as good as mine(I just can't pin point it.) I know it's not the EGR
    or Cat Con (Replaced in '01 car drove it to Nov 2002 then it sat for 2003 &
    2004). I don't know if the oxygen sensor was replaced but more than likely
    it was.

    Thanks Mr. Minnow
    Mr. Minnow, May 29, 2005
  18. You really can't say the EGR and catcon are good just because they were
    replaced. With your HC as high as it is, the catcon could easily be
    cooked. And the EGR valve is only one part of the system; the crossover
    passage and ports (in the intake manifold and the heads, respectively)
    could well be clogged with carbon.

    Don't know where in Ontario you are, but I can recommend a couple of good
    shops in the Toronto area. Canadian Tire does not count as a good shop.
    Daniel J. Stern, May 29, 2005
  19. Mr. Minnow

    Guest Guest

    Where in Ontario? I'm in Waterloo.
    Guest, May 29, 2005
  20. Mr. Minnow

    Steve Guest

    Actually, a converted car WITH a working set of catalysts and correctly
    tuned SHOULD pass with flying colors. But what usually happens is that
    someone replaces the ignition system, disconnects the lean-burn
    computer, and leaves the lean-burn carb in place. That doesn't work so
    good, because the lean-burn carb NEEDS computer control to work right.

    There are two ways to do the conversion:

    1) replace both the carb AND the ignition and do away with the computer,

    2) Replace the ignition, but let the computer continue to control the
    carb. It doesn't "know" that its not still controlling the ignition, and
    will merrily hum along (assuming that the computer is working, the O2
    sensor is working, and the carburetor's VDC solenoid is working.)
    Steve, May 31, 2005
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.