Hi everyone. I'm new to the forum, but not new to Ford trucks. I have a 96 F150, 3 speed automatic w/overdrive that I think may have a vacum problem. It began by not downshifting going up hills at about 60 MPH. I would be down to 40 MPH by the time I topped the hill, pedal to the metal and no downshifting. I manually took it out of overdrive and it went into 3rd fine. I manually put it into 2nd also fine, and upshifted manually as needed. The transmission does not slip and starts out in 1st gear when I come to a stop. I found the black vacum line on the front of the manifold/throttle body had broken off so I repaired it. Everything was good good for a couple days to a week or so. I started having the same problems, plus sometimes when I start away from a full stop, it would shift out all the gears in about 30', or it would wind out 1st gear way too long. Also prior to this the CEL was on and had some stumbling and dying at stop lights. I then found a red vacum line off at the rear of the engine. I stuck it back into what looked like a dead end vacum line plug with a hole in it. The truck ran great for about 2 weeks and the CEL went out within the first 5-10 miles after reconnecting the red vacum line. The same symptoms reappeared. I started driving the wife's car to work while trying to figure this out. One day she needed her car so I took my truck to work. It ran great------ for 2 days. It will run good for a couple days and then act up. I park it for a few days then try again and it will run OK. My work is slow, so I hesitate to run up a big bill from a mechanic. I don't know if this is related, there is a hose that looks like it is silver colored, flexable coming out of a can on the passenger fender wall that has the end of the hose open. The rubber hose goes to the air pump from this can. I feel suction from the silver hose. Should there be something on the end of the silver hose. Sorry for such a long post. Please help if possible.

 

Anything? Please.

 

If you have an overdrive auto there is no vacuum line to it. As a first step you will need to get the trouble codes. If the system is OBD2 you will need to take it somewhere to get it scanned for codes, if OBD1 (unlikely) you can get the codes yourself. The emissions sticker under the hood will say which system you have.

 

Did '96 F-150 come with both OBD-I and II? I was under the impression EPA mandated ALL vehicles be OBD-II compliant by '96 model year. My impression maybe was wrong. impish

 

No, they only came with OBD-II here in the states.

Your impression is incorrect. Light duty vehicles under 8500 lb GVWR (Federal Emissions) were not mandated to use OBD-II. California emission models blur the line of demarcation. Let's stick to Federal emission models....