Well, here's my fun story for today.

My truck is a 94 F250 with the 351. E40d if that matters. For a couple weeks there's been a bad exhaust leak at this metal tube that runs up from the back of the pass. side exhaust manifold, its broken off right at the manifold. The other side looks like someone mickey-mouse repaired it with some clamps, but im sure thats not a perfect seal either. I was going to get shorty headers, but I see none with provisions for this tube that i've never seen on any of my other trucks.

Anyways, since the leak started ive been trying to not drive the truck much, but since today I woke up to 5" of snow on the ground I took the truck to work. It started having a random misfire on the way to work a couple times. Then on the way home it got so terrible that I could barely climb hills, I'm surprised I even made it home it was so frustrating.

On a side note, I've never been terribly thrilled with how this truck has run in the past year. It's had idle issues ever since I bought it. Plugs, wires, cap and rotor are only a few months old but never improved anything. So when I got home today I pulled the codes and got 411 and 412, both related to the idle and a code 172 ( EGO Not switching, lean condition). I couldn't find any vacuum leaks, but im guessing that pipe at the back of the manifold is EGR related.

I searched the forum for the 411 and 412 code and I only found 1 person that replaced the ECM and solved the problem, so I'll probably start there.

 

Your "vacuum" leak is the broken AIR injection tube on the back of the head. It is not in any way related to the EGR. Code 172 is a lean code probably caused by the excess air in the exhaust stream caused by the broken pipe. Codes 411/412 are Key On Engine Running (KOER) only codes. They indicate the PCM cannot control the idle, again probably related to that broken air tube pipe.

 

It's always idled way too low(5-600 RPM), but never misfiring and running like junk like this till the exhaust leak.

All the extra manifolds I have don't have the provision for the AIR tube at the back, just the EGR at the front of the manifold. Would it help at all to replace the manifolds for ones without the provisions and cap off the air tubes?

 

I see no reason to keep the AIR injection system. It's a stop gap measure to compensate for other issues such as poor maintenance. Others may argue to the contrary. Plug the ports on the back of the heads if so equipped. Keep the TAD/TAB solenoids electrically connected to keep the PCM (computer) happy.

 

Edit: Deleted posted on the wrong forum

 

He said the pipe was broken right off at the manifold (not the rear of the heads)
That means it is the EGR pipe that is broken
I'd get the pipe fixed and retest the codes
I'd also leave the thermactor intact (air pump)
We all breathe the same air