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aztec
User
Jun 29, 2017, 10:15 AM
Post #1 of 9
(1843 views)
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working a Volvo 850 with 200,000 miles. new plugs wires cap rotor. ob2 got misfire in 2 and 4 cylinders.want to do vac test but never did one before and never worked on a 850 before. whats the best place to connect to get a good reading. i know what i'm looking for just really want to do the test.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 29, 2017, 10:49 AM
Post #2 of 9
(1840 views)
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Are you sure about the year? They dropped the 850 years before '99.
Just look for a port to direct manifold vacuum. The brake booster hose is a lost resort. Just don't try to drive it anywhere with that disconnected.
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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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aztec
User
Jul 18, 2017, 6:55 PM
Post #3 of 9
(1760 views)
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sorry i believe 97 its a friends car it was having problems starting
scanner read o2 sensor and misfire 2&4 cylinders, flex pipe broken explained o2 sensor, so i cleared codes and it started fine ran great so i sent car to get exhaust fixed. after an hour motor started shaking and fumes starting coming from catalytic converter. scanner read misfire 2&4 again vac test indicated bad valve guides. with new cap wires and spark plugs i didn't install he did i'm thinking bad cat, coil or valve guides. any ideals
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 19, 2017, 12:27 AM
Post #4 of 9
(1738 views)
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Aztec:? Do you really want to take this on and about now possibly end up with $1,000s in parts and things into it and even if all top end is redone find out lower end can't handle it?
First you aren't sure of what year it is nor able to fix or replace whatever exhaust needed now possible serious work on the head you would send out unknown if fit to work with at all yet.
Not criticizing just asking: How are you coming up with a valve guide problem with a vacuum (is that what you really mean?) test?
At least find out what the heck it is. Look at driver's door jam for OE info may not be an OE door but match VIN with others around car. Seems this also was different stuff for models sold to California as well.
Just look up some costs for OE quality parts this would really want or need and better sit down so you don't fall down! You said it's a "friend's" car not even yours so perhaps find out what the budget is to put this in order if the worst case is found out and it is OK to proceed if this gets super costly which is all fine if your friend and your time or others paid or favors still all ads up for a real fix for this,
T
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aztec
User
Jul 23, 2017, 11:09 AM
Post #5 of 9
(1698 views)
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vacuum tester showed erratic needle movement between 7 and 15
at idle if i raise rpms erratic needle movement between 12 and 20
paper work with tester indicates valve glides. i'm new to vacuum testers am just trying to learn. i'm not planning to rebuild motor and don't see how worn valve guides would cause fumes from converter seems like unburnt fuel in exhaust. just seem like a cool puzzle. just trying to learn something and help a friend. car is a 97.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 23, 2017, 11:47 AM
Post #6 of 9
(1692 views)
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Vacuum testing? Yes it's good info but doesn't say what part exactly. Erratic suggest valve issues you don't know exactly why so fast. Crack in a valve or seat, the guide or any reason it can't seal properly.
Two kinds of erratic - 1. sharp movement or a floating movement could just be a serious vacuum leak that might come and go all will burn too much fuel for the engine you would smell or suck in oil which also can smell like an exhaust strong odor hard to differentiate but you'd notice oil consumption or should.
Test more ways while still intact so you have a real good clue of how extensive it will be up to a whole engine redo or just maybe find a well documented excellent used engine that matches exactly - lower miles with known or proven care.
No clue what is available or how much for this car so knowing all you can a lot more than just vacuum alone is in order. Scope to look inside, pull valve cover(s) for evidence, oil pressure test, compression test dry and wet at least that much to decide what to do,
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 23, 2017, 12:44 PM
Post #7 of 9
(1688 views)
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You might want to do a compression test on this next.
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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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aztec
User
Jul 23, 2017, 10:16 PM
Post #8 of 9
(1674 views)
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thanks, sounds like a good place to start. i'm confused as to why 2 and 4 misfire code keeps coming up it has 3 other cylinders no codes. and how dose computer know a cylinder misfires. vacuum tester needle moved sharp and fast would think age and miles would have some valve leakage so that was what i was guessing i'll know when i do compression test. still can't under stand why motor started shaking when exhaust repaired. thanks again
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 24, 2017, 4:34 AM
Post #9 of 9
(1661 views)
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OK - Sharp fluctuation on vacuum test. Forget codes for a bit and think of metal wear not seen by codes that cylinder that's dead you can find out why now. As silly as a valve spring if used (can't know every layout of everything ever made) can to this and not drop a valve and partly work.
Now do the compression test. You'll get some info then move to getting weaker ones to TDC and put air pressure in thru a plug hole and find where it comes out. Either to exhaust or back thru intake. Narrow it down.
Recent exhaust work may have relieved excessive back pressure some needed but just right. It may not handle being normal with the problem to be found.
Said - lots of tests not just one. When a couple come to the same diagnosis then on with the approach for the fix up to knowing it's all over for that engine unknown so far,
T
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