Miss fire problem solved. Finally.

[1994_4x4]

Hopefully this will help others. The truck has been miss firing since I bought it a year ago. I've done a full tune up, intake cleaner, injector cleaner, among other things. It was a 90 degree vacuum elbow off of what I believe is a emissions device of some nature . It now purrs like a kittin, has more power and my fuel mileage increased.

Being under the hood of this thing a lot nothing appeared to be wrong with the elbow, but upon closer inspection it did have some rotting.

Ford wanted 80 dollars for the part, but I ended up going with a 2.99 part from a parts store that appears to be of superior quality. I honestly don't know the function of this emissions device, but it goes from the black box to the intake behind the throttle plate. If someone knows what this is please chime in.

 

[shane96ranger]

I believe that is the elbow for the charcoal canister. You are talking about the "orange" circled piece of hose that is blacker than the rest of the components, right?

 

[1994_4x4]

I believe that is the elbow for the charcoal canister. You are talking about the "orange" circled piece of hose that is blacker than the rest of the components, right?

Correct.

 

[Mark_88]

Yeah, it's basically an overflow...that is supposed to let excess gas go, eventually, back to the tank...good to know it can cause a miss fire though...I'm sure someone will benefit from that knowledge...

If you really want someone to benefit, make a short write-up about it and stick it in the Submit Info for Tech Library or Magazine...at least it won't get pushed 40 pages back to from the day to day that comes into this section...

 

[shane96ranger]

My Brothers Explorer had all of the hoses eaten on the charcoal canister. It was a 5.0, and it didn't affect how it ran. His canister was directly under the battery, and it had leaked on it - and that's what caused it to erode.

I just replaced it all with regular vacuum hose though. It worked out OK.

Sent from a Commodore 64 using a 300 baud modem

 

[Mazda]

This hose also comes undone at the throttle body. A bit hard to get to I finally put a hose clamp on it after about 30 min of cussing at the thing. Watch when you are replacing the PCV valve you can unhook the tube.

 

[adsm08]

Yeah, it's basically an overflow...that is supposed to let excess gas go, eventually, back to the tank

No.

The charcoal canister is in no way an "overflow" nor does it send anything back to the tank. In fact liquid fuel will destroy it. That is why "topping off" the tank after the pump kicks off is a bad idea. It can force liquid fuel up into the carbon canister and ruin it.
It is connected to the tank and the intake manifold by vapor lines. There is another line connected to a valve (on some years) that allows fresh air to be drawn in.

As fuel evaporates in the tank the vapors move up the line and are trapped in the charcoal matrix of the canister. When the appropriate conditions are detected as valve at the intake (purge valve) and the fresh air valve (vent valve) are opened. The engine vacuum pulls fresh air into the evap system and as it passes through the canister it draws the fuel vapor out of the charcoal and into the intake so it can be burnt as fuel.


That is how the more modern ones work anyway. On a 94 the system is far less sophisticated but works on the same basic principles.

 

[Mark_88]

Ah, the mystery explained...thanks!

Mine has a line running to the tank from the canister..and it has a large hose coming off the carb...I've actually seen fuel dumped into the canister from the carb...and thought that the line to the tank was to let fuel or vapor go back to the tank...

But that was caused by the float being set too high and, of course, the needle was dislodged somehow...which resulted in plenty of fuel being dumped directly into my canister...which is probably toast by now...

There was a vacuum line connected to it a long, long time ago...in a galaxie carb far far away...but that was the original carb...and this carb is off an even older (78 Mustang II) vehicle...not sure if I swapped out the canister when I did the carb swap...but at least I know now how it should work...lol

 

[1994_4x4]

This hose also comes undone at the throttle body. A bit hard to get to I finally put a hose clamp on it after about 30 min of cussing at the thing. Watch when you are replacing the PCV valve you can unhook the tube.

So the PCV is in that area? Ha. That's another brand new part I have bought and haven't been able to locate. That hose at the throttle body is going to be my next thing to replace. I'm just assuming it's rotted out too. It looks to be just a straight hose, so I hopefully a vaccum line may work.