87 5th Avenue Emission Problems

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

 

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

ASM2525 TEST

LIMIT READING RESULT
HC ppm 83 197 FAIL
CO% 0.46 0.16 PASS
NO ppm 893 1220 FAIL
RPM 1092 VALID
DILUTION 13.8 VALID

CURB IDLE TEST

LIMIT READING RESULT
HC ppm 300 504 FAIL
CO% 1.50 6.76 FAIL
NO ppm N/A N/A N/A
RPM 854 VALID
DILUTION 17.2 VALID

 

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
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

 

Running lean with a possible inoperative EGR and non functioning
catalytic convertor.

Way too rich.

 

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

 

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.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

 

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.

 

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.

DS

 

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!

DS

 

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.

DS

 

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.

 

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

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
sure.

Toyota MDT in MO

 

Lean misfire *under load*. The 6.7% CO and 504ppm HC are idle readings.

 

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!

 

True enough... your text reply followed the idle reading though.

 

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

 

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

 

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.

 

Where in Ontario? I'm in Waterloo.

 

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.)