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Old 04-05-2005, 01:01 PM
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93 astro 4.3 v6 help

hey there i am having another problem with my astro it has a bad vibration in it like if it is in park and you rev it up a little it vibrates like it out of balance i have had the balancer and flywheel checked they are good i did a tune up put new cap rotor plugs and wires on and it still does it i had someone tell me it could be the egr valve does anyone have any ideas on this it also has the vibration when going down the road but at higher rpms its not really that noticeable every motor i have ever seen that acted like this it was the flywheel or balancer but i am lost on this one so any help would be appreciated thanks

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Old 04-05-2005, 01:05 PM
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Hey there
I would suggest checking your motor mounts. The bushing may be gone or they could be loose. Its a long shot but you never know.
Good luck.
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Old 04-06-2005, 07:32 PM
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thanks for the help ill check that too
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Old 04-06-2005, 08:16 PM
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Vacuum leaks

Doc here,

Check your intake manifold for Vacuum leaks.

Spray with carb cleaner around the manifold area. If it speeds up, you have a leak in that area.

Pull the plug wires with a fuse puller while it's running one by one, the one that doesn't reduce RPM is the offending cylinder.

IF you have a vacuum gauge, measure the vacuum. It should be a steady 17 to 20 in hg at idle. If it fluctuates rapidly, Think Valve/Valve guides.

Do a Compression test all should fall between 125 and 150 psi...less try a little oil in the plug holes, If it rises, you need a valve job.

You could have a blown head gasket between to cylinders, not affecting oil or water, causing the miss.

Hope it helps.
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Old 04-06-2005, 08:44 PM
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Is it throttle body or cpi? If the eighth character of the vin is a Z its a TBI if its a W its CPI. Im almost certain the CPI engines have a balance shaft that runs threw the lifter valley. If that thing has slipped time It would shake bad. Also the CPI is well known for the fuel lines inside the intake leaking fuel and also the CPI unit its self leaks and sticks that will cause an excessive rich condition and it will shake.Yes the EGR valves stick all the time on those engines but that mostly causes poor idle and low vacuum @ idle. Vacuum leaks effect idle mostly not cruising speeds or revving. If you put oil in the Cylinders and the compression rises thats a indicator of bad rings not a valve problem...........Ed
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