At 10:10 PM 05/17/2001 -0500, Pat Washburn wrote:
>James A. Crider wrote:
>
>> Check the O2 sensors -- I gotta think something is latched lean, which
>> causes the ECU to run the engine way rich. Running that rich will lead to
>> really high EGTs, too, which will kill the cats, too (by melting the
insides).
>
>I'm guessing, but wouldn't the exhaust readings indicate this
>condition? According to the guys running the anylizer, everything is
>"within spec".
Yes, but did you SEE the printout and the spec? If all they did was an
idle test, you probably wouldn't notice the problem. There's a tendency to
rely on the machines that go "Bing!" too much and not do proper diagnostics
anymore. This is a shame and can lead to some heinous "shotgun debugging"
sessions, which can get expensive quickly.
>>
>> Are the plugs okay? Something like this, the plugs should be nearly
>> dripping wet with fuel fouling.
>
>They were wet when removed the other day. It is ceratinly running rich.
Okay. This tells me it's either stuck injectors, or, more likely,
something's either starving it for air or otherwise tricking the thing into
running way rich.
>> Vapor cannister purge system is another
>> possibility. But nearly all of these should twig something in OBD-II. Is
>> the crankcase full of gas? Air filter clogged? Exhaust plugged?
>
>Hmmmm. We just had copper exhaust header gaskets installed due to
>failure of the OEM gaskets, and they are blowing by too. No matter how
>they are torqued, they leak. Could there be excessive back pressure due
>to the cats plugging the exhaust? would this cause the gasket blowout?
>You would think we would notice an appreciable power loss if the system
>was clogged. (Tows a 14,000 lb, 45 foot goosneck trailer with no
>problem.) Funny the testers wouldn't notice either? Is there a quicky
>way to check the cats, or flow in general? Will have to check the
>crankcase and the cannister purge system, I don't know.
Best way to check the cats is to pull the Y pipe and check 'em with a
borescope if you can't eyeball the front and rear of each cat. If they're
slagged, plugged, broken up, or (I've actually seen this) rotated within
the converter can, it'll be a problem. It can take varying degrees --
minor, not noticed by seat of pants, to "why won't this truck rev above
1500 rpm?" The manifold gasket failures are certainly a sign that
something is amiss downstream.
>I found it humorous how many people suggested fuel theft! Nice try
>guys, but we towed to Daytona and back and tracked the mileage
>carefully. My boss tows his Pro Stock drag car and can track the
>mileage too. Leaks were considered, but we use this for work and park
>it indoors at night. One would think an odor would be detected if a
>leak. We will take another look just to be sure.
I'd put a locking cap on it just in case. :)
>All signs lead to rich running, but to dump this much fuel in this motor
>and not get red flags during testing is odd IMO. Could it be possible
>that we fixed the original problem, but have since melted the cats which
>is now preventing us from solving the problem??? Thanks Jim, and thanks
>to all for all of the great, and some funny, responses!!!!!
That is entirely possible -- fixed the original cause, but damage was done
already. If the cats are indeed bad, they should be covered by the
Fed-required emissions warranty, BTW.
Jim Crider
autojim@att.net
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