Your IAC seems plenty high and would not seem to indicate a vacuum leak to me. Too high can mean it is too rich.

Well, probably don't need it now, but could have used you a week or two ago! I will keep you in mind next time I need something like that.

 

Rob, So after you fixed your leak to the reserve tank, did your fans stop slowing down or what ever ours is doing? I ask because as you can see by the posts a lot of people notice this occuring and mine is still doing it.

I'm going to put a vacuum gage on the intake and see what it's reading and I'm going to check the lines on the check valve you sent a picture of as well. I will probably try to get the fan control in the dash out and see if there is any indication why that one position doesn't work either.

 

This is most likely leaking at that valve that was pointed out earlier. I had mine crack just after buying the car and it did exactly as you say. Eventually it cracked enough that it wouldn't switch modes. I think that valve costs like $15.00 or so, or you can do what I did and just replace it with a T fitting for about $0.90. I get the quick switch to floor during hard acceleration, but doesn't bother me so I haven't spent the $15 to replace the T with a new valve yet, and probably won't.

The vacuum system in no way is attached to the fan speed. The only thing the vacuum system does is operate which doors open and close inside the heating/AC system. If at any time vacuum is lost in the system it is designed to default to defroster mode....for safety reasons (fog windshield = crash). The fan speed is controlled by an electric switch. If you are sure that your fan is changing speed, then you most likely have an electrical issue and not a vacuum issue.

As far as the AC shutting off at WOT.....It is only the compressor that stops while you are WOT...theoretically you shouldn't feel any change in the cooling operation of the AC...unless you drove longer than a couple of minutes at WOT...which unless you are running a super speedway or driving through Montana, should never happen.

 

I have not recently checked it at WOT and I don't run around at WOT a lot. I have a different cam in my car now and vacuum may be a little different than before. I have noticed that there will be somewhat of a loss of vacuum when engine load is high, like when going up a long steep hill. It is more like a very gradual change and not an abrupt switch to the floor.

So even with a properly functioning system (and the way some people drive their cars ), there might not always be enough vacuum for the controls. If the system is checked and there is no leakage, there is little more you can do.

I am going to check mine again since I noticed the loss of vacuum the other day. I actually broke my check valve when I was doing my cam install (dumb me) and being as cheap as I am, glued it back together. It was holding last time I checked, but maybe it is leaking a little, now.

 

I checked out that reserve canister, and it appeared as if the line going into it was coming off a little bit. after the fix and reinstalling the splash panel, i get a lot stronger air coming out the of the vents with the a/c. But if i stomp on it after about 5-6 seconds of hard acceleration the air still goes to the floor position.

Is it possible that the tank runs empty?

Any help would be apriciated. thanks in advance

 

I did find the vacuum diagram for the HVAC system and it says there are 4 different valves that are actuated by vacuum. heat & defrost, Bi-level, Upper & lower mode and air inlet. Since I dont have a leak but the Bi-level setting does not work I would assume the Bi-level valve has a problem. Testing it is easy but getting to it is another story.

So we have all figured out that the fan doesn't slow down, the vacuum level is dropping and the vacuum actuators are defaulting to defrost position. BTW the description for the heat and defrost position is that it's default is in the middle so that when no vacuum is applied it switches air to both windshield and floor. It requires vacuum to change it's location. The other 3 valves are closed until vacuum is applied and then they open.

In addition I read that the vacuum stored in the vacuum tank is prevented from bleeding back to its source during conditions of low vacuum by tah dah the check valve. Enter the check valve that Rob spoke of before. Since I don't have a leak, could I and others have a problem with the check valve????? Should be easy to check. Lets all now go to our cars and suck on some vacuum lines shall we. Why do I feel like mister Rogers. On second thought, he's dead. I don't feel that bad YET.

Rob? What's your take on this? Did you get my e-mail about the blade?

Dave