On Sat, 28 May 2005 00:48:25 -0400, "Daniel J. Stern"
> wrote:

>On Fri, 27 May 2005, Mr. Minnow wrote:
>
>> 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:
>
>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 a
>
>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
>noncombustion.
>
>(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.
>
>DS
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.