At 08:09 AM 6/14/99 -0700, you wrote:
>My '77 has this exact same problem. It backfires while
>idling down from high RPMs. I removed the air pump
>belt to eliminate the back firing, but don't like the
>idea of removing emission devices. Plus, my air pumps
>works good I don't want it to freeze up.
I suggest removing the pump and check valve. Spray WD-40 or some such
inside the pump, seal it in a ziploc, then save it for a rainy day. :)
>
>I thought maybe the check-valve on the tube behind the
>air pump was shot.... allowing the back-fire.
Can't say. I know that mine goes put-put-put with the pump disconnected.
I think the check valve's purpose is to prevent hot exhaust gases from
ruining the pump itself.
>
>How could the catalytic converter be the cause of the
>problem? Restricted flow?
I think so. (I don't claim to be an expert here.) When a carb runs rich the
Cat overheats and literally 'melts' down into a lump. Instead of flowing
the exhaust through it, it blocks the gassy, hot mixture & it ignites.
Early-eighties midsize GM cars had converters that would melt down so bad
the exhaust would plug up and the engine wouldn't run! So it's not a
unique Triumph problem. That's why early cats had recommended replacement
intervals of 25 - 30k miles.
Atwell (Out on a bit of a limb here theory-wise, but I know my advice is
sound)
|