Good instructor. I even checked the tear-down book and saw the needle test. I missed those days being instructed on narrowing down your diagnostics and making other diagnostics to find the main source. Good Job Ladies!!!! Keep those ears open and clean.
@@winnie51189this is normal behavior in the real world. As a mechanic, we still talk like this and no one bats an eye. Now if this were a college campus, in which they are a bunch of pussies, then that’s another story 😂
As a mechanic here's my two cents. Correct me if i'm wrong. Checking a modern car with a vacuum gauge won't give you an accurate reading unless there is some major mecanical issue such as a broken valve spring, gasket leak or exhaust restriction. However the reason the vacuum gauge isn't ideal on modern cars is because the throttle plate is computer actuated. When the car starts the throttle plate actuates and stays slightly open to keep the ideal amount of air entering the combustion chambers. That decreases the actual vacuum and will give you a reading around the 15-17 inHg (Inches of mercury) which is on the low side even if the engine is healthy. That can mislead a mechanic to think that there are timing issues with the engine.
All accurate, and to take it a step even further, an engine like this is actually an Atkinson cycle. It has so much valve overlap it may not make enough vacuum to run a brake booster. So they add a cam driven vacuum pump to "power" anything using vacuum which is really just the vacuum brake booster in thise case. So overall I agree the vacuum gauge would not be the go to. The scan tool is going to be the #1 workhorse, especially with a relative compression test. But ASE A1 still has vacuum readings on it, and it is still good general knowledge for upcoming techs, so I will continue to teach it at a basic level like this. Good input.
A studied man will see observe the needle shaking and replace all the valve springs. A wise man won't have read the gauge while it was sitting on valve cover in the first place. Theory is good to know but awfully dangerous if its *all* you know.
@@sircob3 These kids are gonna put their vacuum gauge on the cylinder head of a running engine and diagnose it with valve spring failure because no amount of schooling will teach you common sense.
@@jadenwalker6713 I get the point, luckily this program comes with a mandatory internship. I agree 100% on the job experience is necessary. But I have seen the other side where people trained on the job with no training are basically a clone of the person who trained them. Monkey see monkey do. Not sure why they do it but they know they do it because it's what they were told to do. But no argument 😎
@@CurboroughSprinter I've done worse. I pulled apart and entire chassis harness looking for a discontinuity because both brake light bulbs burnt out at the same time.
@@paulkelley86 I HAVE A NISSAN ALMERA 1998 MODEL 1.4CC IT STARTS VERY HARD WHEN IT STARTS IT HAS LOW POWER AND RUNS LIKE IT HAS LOST TIMING.THE VACOUM IS 12 IN/HG AT IDLE .THIS HAS A DISTRIBUTOR AND IT HAS A CAMSHAFT SENSOR IN IT WE SUSPECT THAT THE SENSOR IS GIVING AN IRREGULAR SIGNAL AND THE IGNITION IS NOT AT TOP DEAD POINT.I HAVE GOT COMPRESSION I HAVE 190 ON ALL CYLINDERS FUEL PRESSURE AND DELIVERY IS OK SO WE SUSPECT A ERROR IN IGNITION TIMING WOULD GIVE LOW VACOUM.WHAT IS YOUR OPINION?WON'T A WRONG TIMING SPARK GIVE LOW VACOUM ?WHAT ELSE WOULD CAUSE LOW VACOUM AT IDLE?.I WILL PROBABLY OSCILOSCOPE TO THE SIGNAL BECAUSE I HAVE A PULL UP DESIGN AND SEE IF THE CAM SENSOR SIGNAL IS SIMILAR I AM DIMITRIS mechanic FROM GREECE THANKS MY FRIEND....SORY I FORGOT I SEE AND INJECTORS IS OK.....AND I'M THINKING TO LOOK FOR A CLOGGED EXHAUST AS WELL ALTHOUGH VACOUM SHE DOESN'T SHOW ME SUCH A THING.BUT I WANT TO BE SURE
@@dimisrambodimisrambo7285 the low steady reading and loss of power could indicate valve timing is off, but that would normally result in low compression as well. It would not be that hard to verify ignition timing with a timing light and verify cam timing at the belt referencing the timing marks. Good place start. Your vacuum and compression readings are kind of conflicting. Maybe one gauge is inaccurate.
@@paulkelley86 MAYBE I WILL LOOK AGAIN WITH ANOTHER INSTRUMENT THE VACUUM .I DON'T THINK THE TIMING CHAIN IS GONE I THINK THE SPARK IS GOING AT THE WRONG TIME SO MY COMPRESSION WILL BE OK BUT THE SPARK WILL BE TIMING WRONG,I WILL ALSO SEE THE ADVANCE WITH THE LIGHT AND I THINK I WILL SUCCEED, I WILL UPDATE YOU TOMORROW AS SOON AS I FINISH IT. YEARS AGO I HAD AN OLD AUDI THAT I HAD CHANGED THE ENGINE BUT I HAD INSTALLED THE DISTRIBUTOR FROM THE OLD ENGINE AND IT WENT OUT.SAME SYMPTOMS.HOPE I CAN FIND AN EDGE AND MAKE IT WORK THANK YOU FOR YOUR TIME.I SUBSCRIBED TO YOUR CHANNEL I WILL WATCH YOUR VIDEOS I AM INTERESTED.I WILL TELL YOU MY NEWS TOMORROW GOOD CONTINUE
@@paulkelley86 HELLO MY FRIEND I FINALLY COULDN'T FIX THE NISSAN ALMERA. I CLOSED ALL THE VACUUM HOSES EGR PCV BRAKE BOOSTER ETC AT THE INTAKE MANIFOLD. I TOOK OUT THE EXHAUST AND THE CAR STILL IS RUNNING AT 13 IN/HG AT IDLE.I PUT MY MULTIMETER ON THE L SENSOR AND ON THE ROAD DRIVING AT WOT IT GIVES ME 0.9 VOLTS BUT CONTINUES TO HAVE LOW POWER.SINCE THE O2 SENSOR IS GIVING ME 0.9 VOLTS I ASSUME I HAVE FUEL AND THE MAF IS WORKING SINCE A MAF WOULD NORMALLY GIVE ME LOW VOLTAGE AT WOT.DISTRIBUTOR DOESN'T ADJUST ADVANCE I'M FAR FROM THE POINT MARKS.HOWEVER TIMING IS FINE AS IS CYLINDER COMPRESSION AS WELL AS THE CYLINDER LEAKAGE TEST EVERYTHING LOOKS GOOD.I HAVE NEVER SEEN ANYTHING LIKE IT IN A CAR.SHIFTED CRANKSHAFT GEAR? BAD DISTRIBUTOR?BAD ECT SENSOR?I HAVE NOT DIAGN.TOOL FOR LIVE DATA IS OLD MODEL
Typically I use the vacuum reading to get an idea if the engine has an issue then change over to a different approach. The fluctuation is likely something to do with valvetrain if it is a rapid oscillation. Is it misfiring? If yes, I would pursue DTC check to identify which cylinder or possibly a power balance test if it is not setting codes. Then I would change over to compression and cylinder leakage tests once you identify which cylinder it is. This is all assuming you have a misfire. Which I suspect due to your vacuum readings.
@@paulkelley86 yes sir it's not a rapid fluctuation it fluctuate from 15-17 on gauge I have a p0300 p0171 p0174 codes on a 08 Chevy Express van with 6.0 liter..it has misfire on 2 3 4 and #7 cylinders long term trims on startup are at 25% both banks but come down to about 13 when it gets warmer but when warm ill push gas and trims go back up to 24.. so that i thought maf sensor or fuel but fuel pressure is 58 psi doesnt drop underload and doesnt bleed down. So I went and got a new MAF sensor from AutoZone still no change on trims
@Smith93646 the misfire(s) will cause the low vacuum. The misfire will also cause the fuel trim lean because those non firing cylinders will be pumping oxygen and unburned fuel into the exhaust. The o2 sensor can only read oxygen so the surplus of oxygen will make it read lean, they are blind to the fact there is raw fuel. Don't worry about any sensors. The misfire is the root cause. Diagnose the misfire. I would do spark test on all cylinders to see if the coils are firing. Inspect the spark plugs to see if some are wet with fuel due to no spark or similar. If all spark is good then move to compression test. If compression fails then leak down test the failed cylinders to pinpoint what is wrong. Or if compression passes you can move to checking injectors but that gets a little tricky. I'll walk you through it if you can get the tools to do the tests.
@@paulkelley86 okay thanks brother I don't have compression gauge or the leak down test I can rent from AutoZone though but I'll check coils and plugs and I'll get back with you THANKS
