Exhaust/ Emissions question

[MississippiSlim72]

I am at work in the middle of the gulf of Mexico but trying to figure out what happened to my Bronco...My wife tells me that it started "making noise" by the exhaust and it now stumbles when cruising around 60mph.  I got her to pinpoint that the exhaust on passenger side is rusted out/ has hole in it "where this little pipe comes up out of it"  I am trying to figure out what this "little pipe" is and where it goes.  I can't find a good exhaust diagram online.  Apparently it is around 1/2" dia and leaves the top of the y pipe between the exhaust manifold and the cat converter.  Any ideas?  I know that the EGR goes into the exhaust manifold but off the top of my head I am not sure where this pipe goes/ comes from and if it would make the engine run erratically/ stumble.  Any ideas, suggestions, etc.  One of the reasons I hate working away from home is that nothing breaks til I am out here!  I am probably gonna just get her to take it to my exhaust guy and have him fix it and see if the problems go away.

 

[miesk5]

yo Slim,

What year, engine, transmission?

Parts Break-Out Diagram in 96 5.0L & 5.8L Bronco & F-150, F-250, F-350 Regular Cab, SuperCab and Chassis Cab, 4x2 and 4x4, 4.9L SFI, etc.
Source: by Ford via http://www.thedieselstop.com/faq/9497faq/maint/stj/images/u2989c.gif

 

That small pipe is #4 9J454 Air Inlet Tube from Air Injection System;

The Smog pump pumps fresh air into the exhaust system, to burn left over hydrocarbons, lowering emissions. The computer uses 2 air valves (TAB & TAD) (next to Coil) to control where the air flows depending on engine operation.

Thermactor Air Bypass (TAB) shunts air to the atmosphere, when no air is needed.

When air is needed it sends air to the second valve TAD. Thermactor Air Diverter (TAD) diverts air either to the exhaust manifold, or directly to catalytic converter.

MIESK5 NOTE; If Engine Coolant Temperature Sensor (ECT) is Below 50 degrees F, then TAB is grounded & sends air to atmosphere; If Between 50 and 190 Degrees F, Bypass Valve sends air to Diverter and to Manifold; If Over 190 Degrees F, it is in closed loop & Air goes to Catalytic Converter

You exh shop can weld a new pipe, **** etc.

DTC 311 - "...Thermactor air system inoperable. The computer determined that for some reason the fresh air injection from the Thermactor system was not present. There are several components that make up this system. The initial component is the smog pump. The first checks I would make are the hoses and plumbing from the smog pump back to the diverter valve (behind the pass. cylinder head) and then on to the crossover pipe at the back of the heads and down to the catalytic converter. The check valves that are at the center of the cross over pipe and the top of the metal tube from the cat are often the culprits as they can and do snap in half as the get old. If the plumbing looks to be in good order we can discuss the slightly more complicated aspects of the system. The diverter valve also has two vacuum lines running to it. Make certain they are in place and intact. (Computer needs to be able to control the flow of fresh air by the Thermactor system)..."
Source: by greystreak92

 

[Rons beast]

Hey Slim,

Ditto M5 above....the tube for the AIR, ( smog pump) is rusted, or the exhaust is rusted around it.  This really messes up the cats efficiency, and then the computer is getting all sorts of "bad info" After the repair the codes need to be erased.

Good Luck