'90 F150. - Exhaust System Question

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mpdsville1@yahoo.com - 23 Oct 2005 01:02 GMT

1990 F150 , 5.0 v8, 4x4 , longbox.

Bought it recently for $500. Truck has 170k miles, "Rebuilt Engine
has 65k. Rusty, but runs strong and starts immediately and doesn't
burn oil. No regrets. But its LOUD.

Removed the {completely empty} glass pack and put on a real
muffler. Still loud. Found the problem. Appears there are two
catalytic converters, basically inline. The short pipe between
the two has a fitting on it that vents exhaust gas and noise
straight up into the engine compartment.

God Bless the chilton book I have that completely omits the
exhaust system. (I'll save that for a different rant/thread)

Questions: Where's that hole supposed to go?
Can I cap it off?
If I can cap it, with what?

NOTE: I don't expect many years of service from this truck.
The rust is non trivial.

Thanks ,
Mike D

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Razorblade - 23 Oct 2005 06:51 GMT

Sounds like it would be an O2 sensor bung. Why it would be in between two
cats is beyond me. Usually there is one before a cat and one after the cat
to make sure it is doing it's job but then I have never seen two cats in
series before. Sounds like more "barnyard" mechanic work to me.

Razor

> 1990 F150 , 5.0 v8, 4x4 , longbox.
>
[quoted text clipped - 20 lines]
> Thanks ,
> Mike D

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lugnut - 23 Oct 2005 13:18 GMT

>1990 F150 , 5.0 v8, 4x4 , longbox.
>
[quoted text clipped - 20 lines]
>Thanks ,
> Mike D

That is the air tube from the air injection pump that is
supposed to be mounted to the lower right front of the
engine. It is to provide fresh air to the converter to
complete the combustion process. If you do not have to deal
with emissions inspection and someone has removed the
injection pump, you can put a cap on it. A muffler shop
should be able to do the job.

Lugnut

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Al Bundy - 24 Oct 2005 13:54 GMT

An honest muffler shop will not be tampering with his emissions system.
He could easily plug it himself with a tapped screw or a lag bolt.

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mpdsville1@yahoo.com - 29 Oct 2005 06:38 GMT

> >1990 F150 , 5.0 v8, 4x4 , longbox.
> >
[quoted text clipped - 30 lines]
>
> Lugnut

Thanks again lugnut. The pipe to the airpump is gone, just a
rusty stump left on the exhaust pipe side. I'll cap it
off as I'd rather not shake/bend the exhaust/cat assembly
too much (and wind up with new cracks), and judging by the
rusty stump it will take a lot of force to get the old
fitting off.
The hole is appx 3/4" ID. Any creative ideas how to plug
it?

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