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Original Message
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RE: rough running 390 |
By RC Moser - 01/24/2001 3:18:30 PM; IP 205.188.200.59 |
I think you need to ellimuate the vacuum sources one at a time. (example dissconnect and plug the brake vacuum booster, then any other vacuum sources one at a time and see if it makes any differents). Then I,d do a similated leak down test on the low cylinders. (do this by removing the valve stem from you compression test hose and put the cylinder in question at TDC, Now apply shop air at about 80 PSI or so. Now you can listen at the exhaust valve for hissing air indicating the exhaust valve is leaking, Now listen at the carb. venturi for any hissing air indicating that the intake valve is leaking. and last listen at the oil filler port for hissing indicating the rings are leaking. (Note if you don't have the engine at TDC one of the valves will be held open give you a false reading also a rubber hose or doctor stenscope will magifiy the sound to hear if better. Also, some air will leak pass the rings so a minute amount of air from the oil filler port might be normal.)) Then I double check the points ( contacts for pitting) dwell. And after effectively elimuating all systems I'd suspect the carb. You never mentioned if you have adjustable valve train or standard non-adjustable FE type. You can test your PCV valve by removing it and putting you thumb over the end or by shaking it and seeing if it rattles. Also check all the vacuum hoses on the under sides for cracks including the carcoal cannister and hoses. Hope this gives you some more things to check. |
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