Airflow changes to defrost on long grades

[tommyturbo]

So climbing some of the grades in northern cali and oregon, noticed that after a bit it would slowly shift to defrost, and once i backed off the gas and vacuum built again it switched back. Im assuming that the reserve of vacuum ran out, and thats why it changed. Is this normal for a taurus? Only other time i have experienced this is in my turbocharged mopars, which would do same thing under extended boost climbing hills, or worse case under high boost, blow the vac line off under the dash...but thats another story.

Also if this is normal, which i am guessing it is, does the lack of vacuum affect the opening of the secondaries?

 

[Off Road SHO]

You have a vacuum leak or your vacuum storage canister is closed off. Vacuum just holds the secondaries in the closed position until your engine reaches 3950 RPM's, then the vacuum is taken away and the springs snap the secondaries open.

Tom

 

[pjtoledo]

secondaries are open when the engine is not running.
when the engine starts vacuum closes the secondaries. then at 3500 the solenoid triggers a lack of vacuum that opens them.

 

[pjtoledo]

it appears Tom is a bit faster than me, despite his,,, (no no, don't say it!)

 

[tommyturbo]

Any suggestions as to where the vacuum canister is? And where to look, figure someone may have experience with this.

 

[pjtoledo]

inside the driver front fender, up high and close to the door. the tubing would be highly suspect too.

 

[rubydist]

yeah, it could be anywhere, and since its a small vacuum leak, it may be hard to find. in fact, it could just be the check valve in the canister doesn't seal and allows the vacuum to bleed off back to the manifold under low vacuum conditions.

 

[tommyturbo]

Browsed under the hood a little, things all look ok. But will browse more later...it's harder to look when your on the road.

So traced all the vacuum lines under the hood, all look good. I see a small one that goes into the right fender behind the strut tower, but not sure where it goes after that. Lines I see under hood and through body under dash all look ok. Cant really get to vac canister without jaking car and removing wheel liner, so will wait till I get home.

 

[tommyturbo]

So I have noticed it agan today, driving back home, but different routes. Only happens in 5th with moderate to heavy throttle, can rev in lower gears even with heavy throttle on a hill and it does not change, holds mode like it should. Would think the vacuum drops with load and throttle even in lower gears. Any thoughts?

 

[Off Road SHO]

it appears Tom is a bit faster than me, despite his,,, (no no, don't say it!)

You're dang right I'm faster, you young whipper snapper! Now get off my lawn!

 

[pjtoledo]

You're dang right I'm faster, you young whipper snapper! Now get off my lawn!

Lawn????? you're in Arizona, what is this "lawn" that you speak of?



FYI, my part of Ohio is in a bit of a drought this year. haven't cut the grass for a month.

 

[Devin]

Lawn????? you're in Arizona, what is this "lawn" that you speak of?

Yeah, it should be "get off my rock bed (possibly with a cactus in it)!"

 

[Off Road SHO]

Yeah, it should be "get off my rock bed (possibly with a cactus in it)!"

Yeah, we have "mean" yards here, you have to pay attention if you're going to take a walk in my yard.

 

[rubydist]

So I have noticed it agan today, driving back home, but different routes. Only happens in 5th with moderate to heavy throttle, can rev in lower gears even with heavy throttle on a hill and it does not change, holds mode like it should. Would think the vacuum drops with load and throttle even in lower gears. Any thoughts?

so it sounds to me like its a pretty small leak, because the canister will hold enough vacuum to keep the dashpots in the correct position for the 2-4 seconds that it takes to scream through one of the lower gears, but not for the extended time that it takes to pull a long grade. those are the hardest to find.

I would spray a little carb cleaner on all the vacuum lines and see if its enough of a leak that the rpms will kick up when you spray the carb cleaner on the right spot. otherwise its going to be almost impossible to find until it gets larger.

 

[tommyturbo]

went and used carb cleaner on all the lines under the hood, and the vac canister, no luck there. Also pulled the glove box door out of the way and visually checked all the lines back there, even while the car was running to listen for any leaks, again no luck. Even pulled the dash hvac control and checked the back vac connections there, and again no luck.