I forgot to post the photo (actually I forgot my Photobucket password and ID) but thought the Fordheads here could help me by description.

I have a 1988 F250HD with 5.8L and 5 speed. I'm troubleshooting an idle problem with the IAC, etc. when I noticed a couple things that seemed odd to me.

First, we're looking at the engine compartment from the grill/radiator. There are two canisters on the passenger fender well. One is about the size of the old coffee cans Ford used to use. The other is about 3" long and 2" in diameter. They both have a hose about 3/4" diameter running to one end of each. The small one has a hose nipple on the opposite end that is not connected to anything, just open. The large one appears to be closed except where the hose connects. They are both on the same bracket.

Suspected problem on the small one is that when the engine is running it has air coming out of it enough to make a low purr out of the hose nipple.

Suspected problem on the larger canister is that the closed end (crimped on lid of some sort) has enough rust that it looks like it has rusted a hole in it.

Now for the dumb questions, do I need to replace the rusted out canister and should the small one be pumping out air?

Replacing the rusted one seems obvious. If the small one shouldn't be pumping out air what valve or device is failed that needs to be replaced. These look like they are connected to the AIR pump but could be plumbed into the pipes and hoses that go to some black plastic valves over the driver side valve cover.

Help with advice please.

 

The small one sounds like the muffler for the AIR system. I also have a coffee can looking thing next to my AIR muffler but it has 2 small vacuum lines running to it, it's a vac reservoir. The vac reservoir is metal whereas the muffler is plastic.

 

There's a vacuum canister, the smog pump inlet and the one with the open nipple is the smog pump air bypass outlet. It is normal for it to be open.

 

Thanks for the great info. The smog pump inlet is the one that is rusted out on the bracket end. Do I need to replace this if it has a rusty hole in it?

By the way, as I was scrutinizing other underhood things this weekend I found a big hole in the charcoal canister and a busted hose nipple. The busted nipple appears to be for the line coming from under the cab so it must be the line from the fuel tanks. There is a quarter size hole broken open in the top next to one of the little vent ***** on the top of the canister. I imagine this needs to be replaced???

I assume it is the charcoal canister. It is rectangular with two **** like things on the top and a line coming from the fuel tanks then running up to the throttle body between the two throats of the throttle body. When I unplugged that line from the throttle body this thing ran worse than before.

 

Yes, that's the carbon canister.

Yours sounds to be in pretty rough shape. I'd consider a junkyard replacement if you can find one.