To diagnose catalytics I want to check vacuum level within intake maniold. What is the easiest place (hose) to use to place a T-connector to attach mitty vac?

I'm not sure if on the 95 MY's....but there may be a vacuum hose point on the top part of the passenger side of the intake manifold.

I'm not sure if on the 95 MY's....but there may be a vacuum hose point on the top part of the passenger side of the intake manifold.

Thanks for the hint. I will have 1 more look though I didn't find one when I was looking for one.

There is induction valve vacuum hose though which is split with a little plastic connector to connect the two pieces... I guess that is the place which was intended for measuring vacuum unless that plastic crap serves some other purpose.

But I felt unconvinient to pull those two apart - so I just disconnected the hose which goes on top form PCV -- I seemed to get normal readings. I just wonder now -- if just one of front catalytic converters is clogged -- would I get normal or abnormal vacuum reading: in my case on acceleration (just in park opening throttle since I didn't have enough hoses to bring it out) -- it behaved ok -- idled at around 16 dropped to 0 and then pressure raised even higher (if that is normal) than 16. But I think I heard on passanger side (whenever I close the valve) smth like puh puh puh (sorry for not desciptive presentation) from down where left catalytic is -- I ordered remote temperature sensor to see if pipe before/after it has the same "regime" when cooling down.

You would get the same reading for 1 clogged cat as two. The easiest way to determin if you have a cloged cat is to do a before and after. Take the before reading, and disconnect the exhaust pipes (dont be in a hospital zone or before noon on a sunday).

 

Have you tried hitting the cat with your hand to see if it rattles?

 

 

 

nipper

 

PS try using the power brake booster hose

[...]in my case on acceleration (just in park opening throttle since I didn't have enough hoses to bring it out) -- it behaved ok -- idled at around 16 dropped to 0 and then pressure raised even higher (if that is normal) than 16. [...]

I'm not sure where you connected the vacuum gauge or what exact procedure you used, but 16 inches of vacuum is low, and the zero reading might indicate a problem (depending on how that was arrived at). A more-usual reading is 20 inches or above, with some needle vibration at idle which diminishes as RPM is increased. See my previous post: http://www.ultimatesubaru.org/forum/showpost.php?p=626858

http://www.secondchancegarage.com/public/186.cfm

 

In a healthy engine the vac gauge needle doesnt vibrate at all. Vac reading is usually around 2i inhg.

 

nipper

http://www.secondchancegarage.com/public/186.cfm

Yes, that link is in the post that I referred to as well.

 

 

In a healthy engine the vac gauge needle doesnt vibrate at all.

Umm, there are a few variables. One is how many cylinders the engine has; 4-bangers "pulse" more than 6/8/12 cylinders at the same RPM. Another is where the vacuum is taken off, and whether the hose (or the gauge itself) has any restrictions; a large-bore vacuum connection to the gauge will reflect the piston strokes more readily. Some gauges have built-in restrictions to slightly dampen needle response, so you just don't see the rapid pulses even though they may exist.

 

 

Vac reading is usually around 2i inhg.

Yes, typically near 21 inches of mercury; minimum should be 20, although I've occasionally seen as high as 22.

Yes, that link is in the post that I referred to as well.

 

 

Umm, there are a few variables. One is how many cylinders the engine has; 4-bangers "pulse" more than 6/8/12 cylinders at the same RPM. Another is where the vacuum is taken off, and whether the hose (or the gauge itself) has any restrictions; a large-bore vacuum connection to the gauge will reflect the piston strokes more readily. Some gauges have built-in restrictions to slightly dampen needle response, so you just don't see the rapid pulses even though they may exist.

 

 

Yes, typically near 21 inches of mercury; minimum should be 20, although I've occasionally seen as high as 22.

 

I've seen lower, but i am assuming he doesnt have a cam on this:), if he does i want to know where he got it

 

heheheh

 

Even on a 4 cylinder the needle is rather steady. A vubraion of less then 1/4 inhg is considered steady.

 

Is it instantly 16, or does it start at 20 plus then go down to 16 ?

 

nipper

The manuals state vacuum at idle without ac should be 19.96 in HG or something like that.

 

And yeah, you shouldn't have any fluctuations in vacuum if you're using a good vacuum source.

 

The brake booster is alright, and that other spot you mentioned yarikoptic sounds like it's vacuum, so you could tee into that.

I think one has also to take into account the altitude. If you live higher than sea level the «normal» HG reading will be lower.

One inch lower for each 1K feet above sea level.

And then there is barometric pressure, but I don't know how much a factor that can be.

I think one has also to take into account the altitude. If you live higher than sea level the «normal» HG reading will be lower.

One inch lower for each 1K feet above sea level.[...]

A valid point, but yarikoptic is in Newark, NJ, a port city whose elevation is slightly above sea level.

A valid point, but yarikoptic is in Newark, NJ, a port city whose elevation is slightly above sea level.

 

*snicker*

 

nipper

A valid point, but yarikoptic is in Newark, NJ, a port city whose elevation is slightly above sea level.

;-) That readings were done in Bushkill, PA (Pocono mnts ;-))

;-) That readings were done in Bushkill, PA (Pocono mnts ;-))

With the "winks", I'll assume you're not being serious. If you are, then subtract about 2 inches Hg from what's "normal" at sea level; you should still be seeing 18+ inches, not 16.

With the "winks", I'll assume you're not being serious. If you are, then subtract about 2 inches Hg from what's "normal" at sea level; you should still be seeing 18+ inches, not 16.

I was serious, by smiling ;-)

I will do vacuum reading tomorrow to verify what I saw.

Also remote temperature sensor is on its way so soon I will be able to make sure that the temperatures are right without burning my fingers.

;-) That readings were done in Bushkill, PA (Pocono mnts ;-))

 

:-p

With the "winks", I'll assume you're not being serious. If you are, then subtract about 2 inches Hg from what's "normal" at sea level; you should still be seeing 18+ inches, not 16.

 

Since I started this altitude thing, might as well take it to its conclusion. Bushkill is only 340 feet above sea level, so the effect on the vac reading would be no more than a third of an inch of HG.

Since I started this altitude thing, might as well take it to its conclusion. Bushkill is only 340 feet above sea level, so the effect on the vac reading would be no more than a third of an inch of HG.

I didn't find a ready reference for Bushkill, so the effect on vacuum I mentioned was worst case, based on an entry in the Columbia Encyclopedia: "Pocono Mountains, range of the Appalachian system, c.2,000 ft (610 m) high, NE Pa." The point is, even at that, the vacuum yarikoptic measured was too low, as I wrote before.

 

We seem to have been diverted from the diagnosis by a valid (but in this case not very impactful) point made by frag; I suggest that the vacuum testing be run again, using the criteria previously mentioned. The reading should be close to 20 inches Hg, and remain in that vicinity when the engine speed is raised to and held at 2000-2500 RPM for 15 seconds or so.

Sheesh doesnt anyone use google earth?

 

Elevation 390 feet, found a mountain top at 700 feet.

 

nipper

Sheesh doesnt anyone use google earth?

 

Elevation 390 feet, found a mountain top at 700 feet.

Thanks for the reference, Nipper. No, this particular "anyone" didn't use "Google Earth". By the way, the Poconos certainly have peaks that are about 1,000 feet higher than 700, if that's of any consequence in the discussion of diagnosing a certain Subaru with possible exhaust restriction. :-p

Thanks for the reference, Nipper. No, this particular "anyone" didn't use "Google Earth". By the way, the Poconos certainly have peaks that are about 1,000 feet higher than 700, if that's of any consequence in the discussion of diagnosing a certain Subaru with possible exhaust restriction. :-p

 

Since this is becoming a deversion, this is going to be my last post on the subject, but the first poster said his vaccuum readings were made in Bushkill the lowest point in the area and not on a Pocono's peak. My info comes from The Bushkill's Chamber of commerce site.

Since this is becoming a deversion, this is going to be my last post on the subject, but the first poster said his vaccuum readings were made in Bushkill the lowest point in the area and not on a Pocono's peak. My info comes from The Bushkill's Chamber of commerce site.

I don't see "anyone" having posted that the elevation at Bushkill, PA isn't what either you ("340 feet") or Nipper ("390 feet") said. The point is, whether at Newark, Bushkill, or the highest Pocono peak, the engine vacuum readings shouldn't be as low as 16 inches Hg if all is right.

I don't see "anyone" having posted that the elevation at Bushkill, PA isn't what either you ("340 feet") or Nipper ("390 feet") said. The point is, whether at Newark, Bushkill, or the highest Pocono peak, the engine vacuum readings shouldn't be as low as 16 inches Hg if all is right.

 

We did say 16" was too low.

 

 

nipper