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working with vacuum gauge
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zoggnoff
User
Jun 24, 2009, 12:12 PM
Post #1 of 28
(9260 views)
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working with vacuum gauge
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I can't seem to figure this thing out.
The only reading I could get off the gauge was when I took the PCV valve off and shoved the tapered end fitting into the pcv line, it read 13 in.
Not sure if I had the intake manifold vacuum line, is it the line that connects to the air assembly duct?? because that was 0 in.
and I can't find the EGR at all.
This book gives me one picture, sometimes no picture at all.
it's an 03 eclipse v6 3.0L
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 24, 2009, 12:47 PM
Post #2 of 28
(9252 views)
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Re: working with vacuum gauge
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Vacuum gauge is an excellent diagnostic tool. Not sure if PCV gets true "Manifold Actual Pressure" (meaning vacuum) or not. A pwr brake booster should! Best to use a "T" so the device still is enabled.
FYI: Atmosphere is 14.7 PSI at sea level. Vacuum gauges are measuring "inches of mercury or HGs" so not the same math. At sea level you see the full # which if perfect is 29.92 Hg. Engine vacuum at sea level should be around 18 or so and with a rev show over 20 then be stable again.
You can deduct ONE Hg per 1,000 feet of elevation.
Hope that helped??
What is your elevation? Google Earth will tell you by the foot! I'm at 232' for example!
T
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zoggnoff
User
Jun 24, 2009, 2:27 PM
Post #3 of 28
(9244 views)
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Re: working with vacuum gauge
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google earth puts me at elev 9ft
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 24, 2009, 9:52 PM
Post #4 of 28
(9231 views)
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Re: working with vacuum gauge
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Consider that true readings or "Sea Level" for any use of the device. I do at under 1,000 which is most of the populated world. The day's atmospheric pressure has an impact as well. Once in a while someone will ask me about some #s and live at "mile high" Denver, CO or even higher!
Just for fun - heard that aircraft sets cabin pressure as if you were at up to 10,000 ft and hope you aren't working on a car in the plane but it clearly has a different feel to it to me anyway and air is drier.
Vacuum is a great tool as said for auto engines and air conditioning of course. Look for steady needle (valves good) - drifting needle (a gasket leak) - consistently low - (valve timing off perhaps) -- there's lots.
Learn where to check such that it's "actual" vacuum and not "venturi" vacuum.
Vacuum can tell of an exhaust restriction as well!
T
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zoggnoff
User
Jun 25, 2009, 2:59 PM
Post #5 of 28
(9218 views)
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Re: working with vacuum gauge
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I've been sick for 4 days now. I was in the middle of doing this test when I saw the news today.
wow.
moving on though. The test results were 14 in
bobbled between 12 and 14 in as the idle bobbled between 800 and 1100 rpms
dropped even lower when I unplugged the pcv valve but then the idle speeds up and the in Hg go back up
could this be a vac leak?
if so i'd like to replace all the vac lines, where can i buy new vac lines?
are they all the same size?
they seem to be nearly the same to me
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zoggnoff
User
Jun 25, 2009, 3:06 PM
Post #6 of 28
(9215 views)
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Re: working with vacuum gauge
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also according to the multimeter i used on the TPS it went from 0.2 to 4.8
supposed to be 3.5 to 6.5 k when moving the throttle while hooked up to the meter.
could this be the source of all these damn problems?
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Loren Champlain Sr
Veteran
/ Moderator
Jun 25, 2009, 3:42 PM
Post #7 of 28
(9210 views)
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Re: working with vacuum gauge
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zoggnoff; You should be seeing 17-19hG at idle. As Tom suggested, 'T' into the vacuum booster line or find a manifold vacuum hose. If your vacuum is lower than it should be, it could be caused by poor running condition. Retarded timing, overfueling, misfiring, ect. The TPS voltage wouldn't come into play, at idle. However, as you sweep the TPS with your multimeter, watch for 'glitches'. If there are any, it should be replaced. Also, what kind of symptoms are you dealing with?
Loren
SW Washington
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zoggnoff
User
Jun 25, 2009, 6:00 PM
Post #8 of 28
(9206 views)
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Re: working with vacuum gauge
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Not sure where the booster line is but I was able to get hold of a Factory Service Manual for my specific vehicle, much better pictures of where things are.
was able to pin point all the parts that eluded me before, also according to it the best place to T-in is between the fuel pressure regulator and the intake manifold plenum, which I found and T'd into. Had to trim some tube from my new gauge to make it possible but I was able to get a 14 in reading from it.
Stepping on the gas then letting off quickly went from 14 in hg quickly to 0 in hg then quickly to 25 in hg then slowly back to 14 in hg... but the RPMs drop very slow as well and settle at about 1100 RPMS.
figured it should have dropped quickly in park but didn't.
My symptoms are rough somewhat irradic and sometimes high idle and low vacuum.
the oil leaks and the car smells bad sometimes.
had to recently replace the IAC because it was rough like this before, but instead of idling high it would just stall and the IAC eventually stuck closed and tested dead.
Im affraid that under whatever stress that is going on under the hood that this new part may soon be tossed into the trash with the old one.
part was hella-expensive
What should i do?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 25, 2009, 8:13 PM
Post #9 of 28
(9200 views)
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Re: working with vacuum gauge
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Rough idle and 14 reading - not right. What vehicle and engine are we talking about and how many miles?
T
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zoggnoff
User
Jun 25, 2009, 8:32 PM
Post #10 of 28
(9195 views)
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Re: working with vacuum gauge
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2003 mitsubishi eclipse gt
v6 3.0L
133,000 miles
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 25, 2009, 9:02 PM
Post #11 of 28
(9187 views)
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Re: working with vacuum gauge
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The fact that it could do that snap to 25 is good. Rough idle will not give you a steady, dependable reading but normally would be 17-19 as Loren said.
It's one tool in tool box. Need to chase down the rough idle now - manifold vacuum leaks, tune up items etc,
T
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zoggnoff
User
Jun 26, 2009, 9:41 AM
Post #12 of 28
(9173 views)
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Re: working with vacuum gauge
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Just got in the mail, vacuum pump/brake bleed kit so i can check the EGR & solenoid among other things.
too late in the day to use it now but I did spray carb spray all over the throttle body where it butted up to the manifold and there was no change in idle.
sprayed the manifold itself too but i'm not familiar with that part of the engine so i may not have sprayed the right spots but i did try to spray everything on it that wasn't rubber or plastic because i now the solvent destroys those materials. still no change in the idle.
if it's not the manifold leaking and if I replace all the vacuum hoses and if the EGR and solenoid pass a vac test could it be the spark plugs and or wires, rotor and cap? the plugs were replaced once but the engine has been running hot, very hot. I'd say for the better part of 2 years the engine would overheat until eventually the radiator blew a hole in the top and had to be replaced, still overheated, replaced the thermostat and problem with heat solved.
what steps should i be making?
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Loren Champlain Sr
Veteran
/ Moderator
Jun 26, 2009, 9:46 AM
Post #13 of 28
(9169 views)
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Re: working with vacuum gauge
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zoggnoff; Check for a vacuum leak at the EGR valve, itself. Sometimes a chunk of carbon can get stuck between the pintle and seat. Be careful not to try and apply too much vacuum to the EGR as you could rupture the diaghragm. It may not hold vacuum if it is a backpressure type valve, so don't condemn it if it doesn't. EGRs are usually quite easy to remove and inspect. Once off, if nothing is visible, you can pour liquid in one side and see if leaks through. It shouldn't.
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 26, 2009, 10:43 AM
Post #14 of 28
(9166 views)
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Re: working with vacuum gauge
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Good one Loren. Pintle can be cleaned - push up and down on it with carb cleaner in the inlet side. Real good one will not leak out even thin viscosity of carb cleaner! You may be able to save gasket with high temp Permatex sealer.
Vacuum. That one I disagree with. Diaphragm should hold a hand held vacuum at max. If it ruptured at full vac it tisn't good IMO. Remember or know that atmosphere is only 14.7 psi that we live in. Expressed in "inches of mercury" max vacuum ism 29.92. Engines run on creating a vacuum to draw then compress vaporized fuel and air. Short of pushing air (turbo type/ram air stuff) the most the can get is the 14.7 in PSI and they don't ever show that. Said earlier by Loren engines will show 17-19 Hg at a smooth idle.
Pun intended - vacuum is a cool tool which sucks! Laugh!
T
(This post was edited by Tom Greenleaf on Jun 26, 2009, 10:49 AM)
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Loren Champlain Sr
Veteran
/ Moderator
Jun 26, 2009, 1:48 PM
Post #15 of 28
(9158 views)
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Re: working with vacuum gauge
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Tom; Backpressure type EGR valves won't hold vacuum unless backpressure is present. Weird, I know. Don't ask me how it works. 
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 26, 2009, 6:54 PM
Post #16 of 28
(9152 views)
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Re: working with vacuum gauge
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My only point was 100% vacuum is only 14.7 psi in reverse pressure. Any vacuum item that fails with just that probably tisn't any good.
Please understand we are all here to help and LEARN too! It's a never ending cycle to keep up with what parts do what and what they tolerate.
Old Pharts unite!
T
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Loren Champlain Sr
Veteran
/ Moderator
Jun 27, 2009, 6:13 AM
Post #17 of 28
(9138 views)
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Re: working with vacuum gauge
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>>It's a never ending cycle to keep up with what parts do what and what they tolerate.
Old Pharts unite! <<
Oh, how very true! Didn't mean that thing about the backpressure EGR valve to be anything other than informative. Didn't know if you'd run into one before. Sorry if I stated it wrong.
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 10:47 AM
Post #18 of 28
(9132 views)
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Re: working with vacuum gauge
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We (speaking of regulars) are here to help and we learn too! If any one of us thought they knew everything it's proof we don't!
The only failure is not trying. It's my opinion that any vehicle diaphragm will hold full vacuum. As to back pressures - that's a different problem/issue,
T
PS: Thought for the day. If you took a tire with 1lbs of true air into outer space or a complete vacuum it would read 14. something PSI! A tire at 35 psi would increase by the 14.7 - just examples from my out of space missions
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Loren Champlain Sr
Veteran
/ Moderator
Jun 27, 2009, 11:05 AM
Post #19 of 28
(9126 views)
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Re: working with vacuum gauge
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>> If any one of us thought they knew everything it's proof we don't!
The only failure is not trying.<<
How True!!!! I'm trying to remember my emissions class...Were dealing with a GM EGR valve. With vacuum going to it, it wouldn't open unless it sensed exhaust backpressure and the diaghragm wouldn't hold vacuum unless the backpressure was present? On the other hand, that was back when I had a brain. Probably, 20yrs ago? Hopefully, one of the younger guys with some brain cells left will jump in here. LOL.
Loren
SW Washington
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 11:40 AM
Post #20 of 28
(9123 views)
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Re: working with vacuum gauge
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Feedback EGR valves are very common and you are correct, they won't hold vacuum unless they get exhaust pressure first.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 12:20 PM
Post #21 of 28
(9113 views)
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Re: working with vacuum gauge
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I'm good and confused. I can see that and EGR could be designed to sense pressure one way before activating vacuum to a diaphragm but don't understand if full vacuum it damaging??
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 12:25 PM
Post #22 of 28
(9107 views)
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Re: working with vacuum gauge
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It's not being damaged. The vacuum just get bypassed until the exhaust backpressure closes the vent.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 12:49 PM
Post #23 of 28
(9100 views)
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Re: working with vacuum gauge
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Got it - thanks!
Tom
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zoggnoff
User
Jun 27, 2009, 5:09 PM
Post #24 of 28
(9089 views)
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Re: working with vacuum gauge
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book says 5-to-10 in-Hg vacuum to EGR valve with engine idle, if speed does not drop considerably (or stall) indicates possible faulty EGR valve, blocked or plugged EGR tube or passage in intake and exhaust manifolds may be plugged with carbon build-up.
EGR vavle unbolted apply 15 in-Hg vacuum, if stem moves it's good.
Picked up 3 spark plugs and some anti-seize compound for the front. I figure why not change the easiest plugs first, see if any changes, they were $2 a piece
had a random misfire code at idle again, cleared, didn't come back.
have not tested nor replaced parts yet (plugs included) still waiting for some tools to arrive
(This post was edited by zoggnoff on Jun 27, 2009, 5:11 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 27, 2009, 8:54 PM
Post #25 of 28
(9076 views)
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Re: working with vacuum gauge
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Interim note: Watch out for anti-seize (alum stuff) - make sure on threads only - It can conduct electrical energy and mess us diagnostics.
T
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