Engine Vibration
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07-17-2009, 07:59 AM
#8
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Looking at the video, it seems regular enough to be one cylinder thats giving trouble. Have you checked/adjusted your valves? I would do a compression test. Also makes me wonder about a lob out of spec on one of your camshafts. I had a cam go flat on a chevy v8 and it vibrated like that before it wore to the point it wouldnt open the valve any more........regards.......Rick
07-18-2009, 06:20 PM
#13
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Holy Crap that is a clean engine!
Have you replaced your distributor cap & rotor and all the plug wires? Sounds like a lot of your problem was plug misfiring....
Have you replaced your distributor cap & rotor and all the plug wires? Sounds like a lot of your problem was plug misfiring....
07-18-2009, 06:59 PM
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i have a couple of suggestions you can try. first put your hand over your exhaust pipe while its running, you might have a friend rev it up to about 2000 r.p.m. and hold it at that speed. with your hand on the pipe you are seeing if at any point the exhaust actually sucks your hand in. if it does its probably either a stuck or a bad valve.
my second suggestion to try is remove your serpentine belt and start the motor and see if it goes away. one of your pulleys might be bad. it could be a standard motor pulley or it might be something like the pulley on a/c, power steering, or whatever.
you might also look at your harmonic balancer it could be bad also
my second suggestion to try is remove your serpentine belt and start the motor and see if it goes away. one of your pulleys might be bad. it could be a standard motor pulley or it might be something like the pulley on a/c, power steering, or whatever.
you might also look at your harmonic balancer it could be bad also
07-18-2009, 11:46 PM
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Sort of agree with replacing things to cure the 'dookie'... however, I'm not sure the radiator is the issue. That is rust, aka iron oxide, ferric oxide or ferrous oxide depending on who you speak with... or if you haven't had the vehicle a long time could be one of the several stop-leak products (probably bars-leak) or corrosion of the engine block since it's the only part of the cooling system made out of iron. Arec you using new, proper coolant every time you flush or straight (or distilled) water?
Your compression numbers don't look all that bad for that many miles.
Your 'vette guy is pretty accurate in his assessment. Flex plates are dynamically balanced when manufactured as are torque converters: look for drill marks in the flex plate ring gear or weights added to a converter as proof of such.
But....
Our converters use a flange, button, mushroom, whatever you want to call it, on the engine side of the converter to locate itself centric to the crankshaft (like the pilot bearing does on a manual trans equipped vehicle) and there are several different converter flanges for our trucks. A converter with an inappropriate flange (etc.) on the crankshaft end may end up wobbling a bit and the flex plate will absorb a lot of the vibrations.
Now here's where the 'vette guy may be on to something:
... a partial combustion event can cause a periodic loss of power on one cylinder. Imagine one injector spraying incorrectly causing the fuel mixture to not be as completely burned as the other cylinders. This means a loss of power in that cylinder and as such less 'torque', or power applied to the crankshaft, during that cylinder's power stroke. Guess you could call it a partial misfire. This can appear as a vibration which varies with engine RPM and whether the torque converter is locking: an open converter will absorb most of the vibration but a locked converter will transmit 100% of the power variations to the driveline. But, were it a cylinder misfiring, this would also result in rich exhaust emissions from the errant cylinder. The ECU would lean the "collective" fuel mixture to compensate for this and this would cause a slight lean condition in the other cylinders, something not all that easily detected by inspecting the spark plugs. Valve clearances as well as poorly performing injectors can cause the same sort of issues. (Getting the pic of why dealers charge so much for troubleshooting yet?)
Now, how to find out what's really going on....
How about posting pics of the spark plugs?
Your compression numbers don't look all that bad for that many miles.
Your 'vette guy is pretty accurate in his assessment. Flex plates are dynamically balanced when manufactured as are torque converters: look for drill marks in the flex plate ring gear or weights added to a converter as proof of such.
But....
Our converters use a flange, button, mushroom, whatever you want to call it, on the engine side of the converter to locate itself centric to the crankshaft (like the pilot bearing does on a manual trans equipped vehicle) and there are several different converter flanges for our trucks. A converter with an inappropriate flange (etc.) on the crankshaft end may end up wobbling a bit and the flex plate will absorb a lot of the vibrations.
Now here's where the 'vette guy may be on to something:
... a partial combustion event can cause a periodic loss of power on one cylinder. Imagine one injector spraying incorrectly causing the fuel mixture to not be as completely burned as the other cylinders. This means a loss of power in that cylinder and as such less 'torque', or power applied to the crankshaft, during that cylinder's power stroke. Guess you could call it a partial misfire. This can appear as a vibration which varies with engine RPM and whether the torque converter is locking: an open converter will absorb most of the vibration but a locked converter will transmit 100% of the power variations to the driveline. But, were it a cylinder misfiring, this would also result in rich exhaust emissions from the errant cylinder. The ECU would lean the "collective" fuel mixture to compensate for this and this would cause a slight lean condition in the other cylinders, something not all that easily detected by inspecting the spark plugs. Valve clearances as well as poorly performing injectors can cause the same sort of issues. (Getting the pic of why dealers charge so much for troubleshooting yet?)
Now, how to find out what's really going on....
How about posting pics of the spark plugs?
07-19-2009, 06:03 AM
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