>The idle speed gives it away. You've got a huge vacuum leak. These trucks
>have a systemic problem where you usually get huge vacuum leaks between the
>upper and lower intake manifolds. Probably that's where the trouble is.
>> The idle speed gives it away. You've got a huge vacuum leak. These trucks
>> have a systemic problem where you usually get huge vacuum leaks between the
[quoted text clipped - 4 lines]
> The SnoMan
> www.thesnoman.com
Would that cause the latent shifting problem with the tranny too? As
far as the vacuum leak- you mean between the air plenum and the intake
manifold? Or between the intake manifold and the valley?
TIA
phaeton - 10 Jul 2006 17:30 GMT
> Would that cause the latent shifting problem with the tranny too? As
> far as the vacuum leak- you mean between the air plenum and the intake
> manifold? Or between the intake manifold and the valley?
>
> TIA
Yes (regarding latent shifting). The transmission uses engine vacuum
to sense throttle input, and aggregates this with the roadspeed
indicator (governor or output shaft sensor) to determine when to shift.
Typically, low vacuum tells the transmission that you've really got
your foot into it, so it delays the upshift (tries to wring more
acceleration per gear vs. economy per gear). In addition, low vacuum
and low roadspeed makes the transmission think you're pulling something
heavy or ascending a steep grade- yet another instance where you'll
want to stay in a lower gear.
So in this case, the huge vaccum leak is confusing the transmission,
and making the engine run like crap.
-phaeton
SnoMan - 10 Jul 2006 18:05 GMT
>> Would that cause the latent shifting problem with the tranny too? As
>> far as the vacuum leak- you mean between the air plenum and the intake
[quoted text clipped - 16 lines]
>
>-phaeton
Yes and look for a leak in line going to tranny or a bad vacum
modulator on tranny itself.
-----------------
The SnoMan
www.thesnoman.com
Marlin Singer - 10 Jul 2006 21:36 GMT
>>> Would that cause the latent shifting problem with the tranny too? As
>>> far as the vacuum leak- you mean between the air plenum and the intake
[quoted text clipped - 21 lines]
> The SnoMan
> www.thesnoman.com
I would look carefully at all the vacuum lines. You stated this sat for
quite a while. Mice and squirrels love to chew on things like that.
Joe - 11 Jul 2006 06:06 GMT
>>> The idle speed gives it away. You've got a huge vacuum leak. These
>>> trucks have a systemic problem where you usually get huge vacuum leaks
[quoted text clipped - 9 lines]
>
> TIA
Between the two parts of the intake manifold. I guess you could say between
the plenum and the intake manifold. There's a big gasket in there with 8
holes in it. When you take the manifold apart you'll see where a big chunk
of it got sucked into the motor (probably).
ECS - 11 Jul 2006 16:48 GMT
>>>> The idle speed gives it away. You've got a huge vacuum leak. These
>>>> trucks have a systemic problem where you usually get huge vacuum leaks
[quoted text clipped - 13 lines]
> holes in it. When you take the manifold apart you'll see where a big chunk
> of it got sucked into the motor (probably).
Ok, after more troubleshooting, here is what I found. When the engine
is doing it's high RPM idling and I pull the control cable to the IAC
the engine will shut down. Something is telling the engine to rev that
high I believe. If I did have a massive vacuum leak, wouldn't pulling
the IAC have no effect on it then? Any ideas?
SnoMan - 11 Jul 2006 19:09 GMT
>Ok, after more troubleshooting, here is what I found. When the engine
>is doing it's high RPM idling and I pull the control cable to the IAC
>the engine will shut down. Something is telling the engine to rev that
>high I believe. If I did have a massive vacuum leak, wouldn't pulling
>the IAC have no effect on it then? Any ideas?
The IAC also add fuel as well it bypass for idle control and when you
pull it this is lost. YOu need to find vacum leak between engine and
tranny or if modulator on tranny is bad because it wiull shift exactly
like your is when there is a problem in these circuits or devices.
-----------------
The SnoMan
www.thesnoman.com
ECS - 11 Jul 2006 19:58 GMT
>> Ok, after more troubleshooting, here is what I found. When the engine
>> is doing it's high RPM idling and I pull the control cable to the IAC
[quoted text clipped - 9 lines]
> The SnoMan
> www.thesnoman.com
Okey. I will pursue the leak some more than. I had a visit from a
neighbor yesterday who suggested pulling the IAC.
Now all I need to do is locate my missing shop manual for this truck.
Last time I used it was for the waterpump fiasco a few years ago.
Suppose I gotta clean the garage then. crap...
ajeeperman@comcast.net - 11 Jul 2006 08:06 GMT
you can spray some wd40 around the manifold and when it finds the vacuum
leak, the engine will rev up. this will narrow it down so you can see the
bad place or even fill it with a good sealer that will harden and stop the
leak for awhle.
old john
Hello, ECS!
You wrote on Mon, 10 Jul 2006 10:56:20 -0500:
E> SnoMan wrote:
??>> On Sat, 8 Jul 2006 23:44:12 -0400, "Joe" <Joe@dontspam.net> wrote:
??>>
??>>> The idle speed gives it away. You've got a huge vacuum leak. These
??>>> trucks have a systemic problem where you usually get huge vacuum
??>>> leaks between the upper and lower intake manifolds. Probably that's
??>>> where the trouble is.
??>>
??>> I agree that this is the first place to look.
??>> -----------------
??>> The SnoMan
??>> www.thesnoman.com
E> Would that cause the latent shifting problem with the tranny too? As
E> far as the vacuum leak- you mean between the air plenum and the intake
E> manifold? Or between the intake manifold and the valley?
With best regards, ajeeperman@comcast.net. E-mail: ajeeperman@comcast.net
phaeton - 12 Jul 2006 04:52 GMT
> you can spray some wd40 around the manifold and when it finds the vacuum
> leak, the engine will rev up. this will narrow it down so you can see the
> bad place or even fill it with a good sealer that will harden and stop the
> leak for awhle.
> old john
I couldn't remember if it was WD-40 or starting fluid. ;-)
You can also rent a vaccum gauge from most parts stores too, if you
want a second opinion to what everyone says here.