Strange BUCKING...Vacuum leak?

[YourNameHere]

So I was stopped at a traffic light on Friday when my car started bucking back and forth. Felt like someone was behind me pushing the truck repeatedly.
I noticed a slight hiss every time I touched the gas pedal when I left in the morning. Yet, everything ran just fine.
That is, until the bucking started. It did it on 3 occasions on the way home. If I put my foot on the brake and gently touched the gas, the bucking went away.

I went out today and found that one of the vacuum caps was missing from the vacuum tree, and 1 was cracked.
Would this be the cause of the intermittent bucking? I'm positive it was the cause of the hissing.
I just don't want to take it out and have it shlt the bed on me in the middle of nowhere.
I know my fair share about Fords, but never encountered a problem like this. Not sure if it's trans/torque converter related, as this is my first Automatic vehicle.


Thanks for any help in advance!
-P.J.-

 

[Blacksheep Josh]

Yup, they're known to fall off. I know exactly how you feel, like the engine wants to die but can't make up it's mind.

It's pretty easy to cap off again, I just took one of the other hoses that had some slack in it, cut some off, stuck it where the cap was, and then put a bolt in the hose.

Here ya go, this is what it looks like now. Notice the rear and front have about an inch of tubing, then the bolt in the end to cap it off.

 

[YourNameHere]

Oh ya, I know the old vacuum hose/bolt trick! I've used that many a time. LOL After all, i am a Ford guy.
So, you think that was the problem?

 

[94Jo]

Just a FYI, a pencil eraser (the cone kind you attach to the end of the pencil) is a perfect replacement, plus it adds that little extra color spice to the underhood! lol

 

[Blacksheep Josh]

i'm almost positive that would be the problem. it makes sense, i had it doing for a week and i could NOT figure it out, then all of a sudden i just happened to look on the vacuum tree and saw the opening. just see if something fell off, or a cap came loose

 

[BP_93explorer]

also check to see if there is fluid making it slick. sometimes the vacuum modulator on the tranny stops working right and sucks tranny fluid into the tree. i kept having the same problem until i asked here and was told about the modulator. it is possible it just blew off by itself though

 

[YourNameHere]

^^^
What's the deal with the vacuum modulator?
Is it expensive? Tough to change/locate?

 

[YourNameHere]

Just a FYI, a pencil eraser (the cone kind you attach to the end of the pencil) is a perfect replacement, plus it adds that little extra color spice to the underhood! lol

I've heard of that method too, but not exactly my style of fixing things.

 

[BP_93explorer]

I don't remember the price (I don't remember being mad about it) but it is a pain to replace. They may not even be your problem though. I wouldn't worry about it unless you feel the fluid on the tree or you keep having lines or caps pop off.

 

[YourNameHere]

Now I'm a little worried the cracked vacuum cover had some greasyness to it, but then again, I just add trans fluid so i probably had it on my hands....
I hope.

 

[Bayoubob45]

Vacuum leak

I have had repair work done several times now to fix bucking/lugging problem with my 93. New MAF sensors, tune up, plugs, wires, throttle body cleaned/checked, computer reset for tranny shifting points...in short mechanics have done a lot of work and $$ to no avail. Problem returns in short order. If i disconnect the MAF and manually shift the tranny car runs OK, only minor bucking - that was a hint from last mechanic in case I had an emergency; then, holding brake and increasing rpm to about 1200 while stopped gives me smooth start if I don't try to accelerate too fast.

Vacuum leak sounds like source, will check that out, good hint. All this time and effort and it could be something that simple.

PS-if that is the problem I have found that golf tees come in very handy to plug broken/open vacuum lines. If you don't play golf, borrow a handful from a friend to keep around the garage. They have lots of other uses from time to time.

Bayoubob45