I have a 93 f250 with a 351 v8 and it's 8600 gvw. Anyways, I pulled the engine out months ago and am reassembling and I'm almost done, 1 thing I cant figure out is where the two air tubes from the Cat Convertor hook up to? I have them on the cat and then going up to another piece and then nothing. Can someone take a picture of where theirs goes, i hope I didn't misplace a peice,. thanks
I threw mine away too, but if I remember right there should be a metal tube that runs from head to head across the back of the motor and it has a large hex fitting sort of in the middle. That fitting hooks up to a mass of tubing and vacuum valves that mount over where your coil is. The two tubes from the cat connect to the mass of tubing. I still have the pieces in my garage and I guess I could lay them out on the floor and take a pic if you still need one.
If you are not connecting the tubes at the cats then there's no point reinstalling all the other hardware.. pumping air to the cats is the only reason the system exists. The motor will run fine without it too as long as any holes in the exhaust system upstream of the O2 sensor are plugged and there are no vacuum leaks. For the record the AIR system on HD trucks is configured a little differently than the 1/2 tons, instead of pumping into the back of the heads it usually goes into the exhaust manifolds by the collector, and the diverter valves are mounted on top of the engine instead of behind and beside it. There was a posting here a little while ago with pictures of the smog setup on an F250 but damned if I can find it now, maybe do a search yourself if you really want to see it.
Are the wiring connectors for those valves still in the same place? I was going to reccommend that he order three of those large resistors from RJM to put across the connectors to keep the check engine light off. I've done it to mine and they work fine. I just shortened the leads and soldered some mini blades to them. Plugged them in and taped them up. No codes after I did that.
My truck was running fine until the PCM started messing up. I've also removed the EGR and the smog pump. Got rid of quite a bit of engine bay clutter.
The air control solenoids are in the same place.. next to the coil. I know some guys are hell bent on removing everything but if you leave them there and keep them electrically connected that will keep the CE light off too.
The idea behind the whole AIR system is to pump air (thus oxygen) in the cats and the back of the heads (or manifolds on the HD trucks) to help the cats start their chemical reactions faster on a cold engine. Once the engine warms up the air supply to the heads/manifolds/cats is shut off and everything pumped by the smog pumped is just being vented out into the atmosphere again. The AIR system can be safely removed from the truck, without affecting emissions testing results, provided testing is done with the engine fully warmed up (like it should be done anyways). There is a catch tho - you can remove the plumbing and the diverter valves, and you obviously plug any loose ports in the heads and manifolds and cats, but you have to leave the control solenoids plugged in their harnesses - the PCM really only cares about "seeing" them through the electrical signals it receives from them (it grounds them to trigger them), so as long as the harness is still plugged in then you can remove everything else (including the rats nest of vacuum lines) and there will be no error codes in the PCM.
Oh yes, you can only do this is counties where there are no visual emissions checks, as not having the AIR system will in many cases give you an automatic fail even tho your truck runs perfectly good and passes the actual sniffer test with flying colors...
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