There is a vacuum line that was disconnected on my 1992 F-150 and I'm wondering if someone can tell me where it goes. Here's a link to some pictures of my truck, the vacuum line I'm talking about is in the 4th picture from the top.

http://www.cardomain.com/ride/2521409/1

One line comes from the vacuum canister on the fender, then it Ts off. One end goes to the manifold, and the other is disconnected?

Any help is appreciated.

 

Looks like things might be a little different on your 4x4 than they are on my 4x2. However, normally, the vacuum line that comes off the manifold directly to the VRES has a check-valve in it. Then a line goes back from that over to the TAB/TAD/EGR valve assembly, mounted at the back of the left bank valve cover, right next to the coil. My VRES is mounted on the right fender (passenger side), not too far from the EGR, and the check valve is built into the fitting on that.

BTW, I noticed the red plug wires. Are those the really nice MSD wire set? If so, don't kid yourself. Let the truck idle in a dark garage, and you'll see why. Get some good Motorcraft 8 mm or 9 mm wires. You won't regret it. Been there, done that. Dunno why, but the Motorcraft wires seem to be the only ones that work on these trucks without misfire or leakage. If you're having idling/driveability issues, the vacuum leak is certainly an issue, but I'd make sure to put nothing but Motorcraft wires on it. Make absolutely sure, if it's the 5.0, that you keep 7 & 8 separated, too. BIG TIME cross firing problems if you don't. I liked the MSD cap/rotor over the Motorcraft, though. The MSD has copper (not plated) terminals, not the normal aluminum found on the Motorcraft caps.

 

Ok, I'll check around the EGR.

Yes, the wires came with the truck when I bought it. I think they may actually be the exhaust "tick" that I'm hearing.

 

brian do you know what item number that cone filter is? or what make it is?


thanks

 

Hi there, it's a K&N filter setup. Unfortunately I don't know the part number for it.

 

Probably should look a little closer at the small rack with three valves on it. (looks like 4 valves, but it's actually 3). Mine is plastic tubing that's color coded, but looks like yours may have been replaced with rubber. I believe the one going to the VRES is black, and the one going back to the valve header is red. TAB green, TAD is yellow, and EGR is also green. (Don't quote me on the colors, though) I'm still confused why Ford didn't mount the valve header next to the VRES to shorten up some of those vacuum lines, and make them less prone to breakage and leaks. Silly me for thinking that way.

 

I saw your reponse to another post about engine surging and I'm wondering if I have additional vacuum issues too. I have the same problem with the surging and the stalling, only when the truck is hot and it doesn't happen all the time. It also doesn't want to shift into 3rd when it's acting this way.

I do get a check engine light with code 122 for the TPS when it acts up, but I'm not so sure that the TPS is the actual problem.

 

The TPS is not accessible unless you pull the throttle body, so obviously, a lotta folks don't wanna replace it unnnecessarily. However, look at the cost of replacing that, and the cost of letting a dealer work on it, and I think that will make your mind up real quick. My '92 gives 2 digit codes, so yours was probably built after mine, thus some of the minor differences. But if mine were pointing at the TPS, I'd swap it. The EEC-IV doesn't lie often.

 

brian, there should be a vacuum diagram under the hood of you truck. I have a 93 and mine is on the underside of the hood towards the back. It has all the specs for your engine on it. If you study the diagram your should be able to trace them all out and check them closely for cracks. I had a severe driveablity problem with mine that turned out to be a vacuum problem. The best way to check them is to get a handheld vacuum pump and check each line with both ends unplugged from the engine then plug one end and put vacuum pump on other. This is how I found a hard line that was melted and a rubber line that had a small split. I could not hear a leak. FYI

 

The item you are calling the vacuum canister is your speed control diaphragm and I think you are asking about the hose going towards the front of the truck. I think that hose goes to a vacuum reservoir for the speed control system and has nothing to do with the TAB/TAD/EGR valve assembly.

This speed control vacuum system is not in the diagram under the hood.

 

Thanks for the clarification subford, that definitely helps knowing which component I'm dealing with. I'll have to look around for a reservoir, haven't been able to find anything that is missing a line so far.

I did, however, replace the TPS and that seems to have solved my idle/surge issue. It was pretty easy to replace too.