Forgetful

You may have a vacuum leak. They can be hard to locate. I've had success using a water spray bottle before. Have the engine running. If you spray water around the vacuum lines and or attachments, nothing will happen until you hit the leak. Once you spray the leak it sucks the water in and the engine will miss badly or die. Just spray small areas. Hope that can help.

blade z51

Thanks, I'll try and see what I can do.... Who knows, it might be connected to my fairly poor fuel economy too.......

theshummer

I finally got a chance to work on mine. I checked out the vacuum tube to the solenoid and it literally cracked when I started messing with it. The exposed portion of the plastic tube had lost all of its flexibility and just began falling apart. The part inside the wiring/tube bundle is still in good condition. So, I cut it there and replaced the section with a standard black vacuum tube using electrical tape. I tried to salvage the original piece that connects to the solenoid too, therefore saving some time trying to rig a new connection. The problem has gotten a lot better, but it's still there. Instead of auto-changing around 55 mph, it doesn't start now until about 70 or so. I think my tape job may have a few leaks, so I'll re-tape when able and hope that fixes it. If not, I'll get rid of the original connector to the solenoid and just go tube-to-solenoid directly. For now, I'm happy. I'll post pictures of the job when I get a good outcome.

blade z51

The vacuum tube in mine does not appear to be cracked or leaking. However, when I moved the tube and rotated it a bit, the engine idle speed changed a little. There might be a leak where the tube connects to the vacuum actuator, but I'm still puzzled by the loss of vacuum coincidental with the throttle position. It basically acts just like the old cars of the '50s and before that had vacuum actuated windshield wipers. The would go like crazy when you let up on the gas and stop when you opened the throttle. Pretty much exactly when you needed them most .
Right now, the vents blow great when the engine produces the most vacuum and the airflow goes to the defrost whenever the engine is under greater load. I think that there must be a leak or malfunction with the vacuum accumulator (or whatever that is called).

Correction:

I went back and pulled the hose off the vacuum solenoid. When I examined it closely I saw that it was disintegrating in the area where it bends coming out of the loom... I put some teflon tape over the damaged area and secured it with electrical tape. I'm going to the auto parts and see about purchasing a piece of replacement tube as well as whatever I need to connect it to the remaining "good" hose.

blade z51

I have replaced the the damaged section of vacuum line with a 5/32 dia airline. I used 2 sections of 5/32 I.D. air hose to join the new air line to the ends of the cut off damaged section.
I'm still not sure if this will work because I believe that there are more leaks of vacuum elsewhere... I'll try the repair I made and see what happens.







I also took pictures of the damaged part of the old vacuum line. They seem to literally rot away. Perhaps it ozone damage, I don't see how UV radiation can get to those since they are under the hood....





Also, I had to remove the black tape from the wire/airline loom to get back to undamaged area of the vacuum line. I wrapped it back up after repairs, but I used black electrical tape. The stuff that was there looked much better than the crappy electrical tape I used. Anybody knows where to get the good stuff ?

theshummer

Your old tube looks exactly like mine did. Great pics.

I connected mine two different ways, one of which I've decided was not good. So, the "good" way: I bought a 1 foot length of 1/8" I.D. vacuum hose. When I cut the original plastic tube, the new hose fit around it easily, even a little too loose. So, I wrapped a short bit of electrical tape around the plastic hose and then pushed on the new rubber hose over it. It was quite tight. Then I followed that up with another wrapping of electrical tape around the new rubber hose to ensure a tight seal and not let out the vacuum. Then I added a third, longer piece, that basically bridges the two hoses and serves to tape the two together and not slip off. Does all of that make sense?

On the "bad" tape job, I did not use the first piece of tape around the old plastic hose, so I think I'm still getting a little leak around that connection. My bad job is where I cut the two hoses to connect near the bundle.

I also used the original connector to the solenoid/actuator. I left just about an inch of old plastic hose so I'd have enough to slip inside the new rubber hose, then taped using the "good" method above.

Hope this all makes sense!

Forgetful

I may be off base here, but my only objection would be all that tape. Remember this is a vacuum line not a pressure line. The vacuum wants to pull the hose tighter against the fitting. All the tape could add a crease and make a leak. As long as the original plastic is solid and round the 1/8" vacuum hose will work fine over it. On the actuator too. If not, I'd cut up the line till I found it good and solid. The vacuum will hold it tight. Just my 2 cents.

theshummer

Totally agree with your idea. Allow me to clarify: each piece of tape was very short. I would not call it an excess and I was very careful to wrap it smoothly. The old hose was so loose inside the new hose that a vacuum would have been impossible in that condition, so I was forced to come up with something. On top of that, anything would have been better than the rotten tube I had before!

If I continue to have issues, I'll get some silicone sealant and spread that lightly over the connections.

blade z51

What I discovered was that the original line is about .150" dia which is less than 5/32 but larger than 1/8. The 5/32 black air hose was a little loose over the original tube, but it just slipped as much of the old tube as possible inside. the 5/32 air tube was pretty snug in the air hose. I used no tape on the repairs except over the wire loom...

OK, here is an update. I drove the truck tonight and tried the A/C. While it does work more than it did before I discovered the disintegrating tube and repaired it, it still does the same thing. When I step on the gas to accelerate or maintain speed uphill, the A/C shifts to the defrost vents. It seems that there is no vacuum reserve for times when the engine does not produce it... Any ideas where to look for the problem??

W Ligon

My '92 F150 does the exact same thing and guess what?.... The vacuum line looks exactly the same way and is rotted in the same place.