Art_H Posted May 30, 2014 Share Posted May 30, 2014 Mack 300+ ETAZB673A on A RS600L '77.Just experienced an upper RPM 1600-2000 exhaust fluttering noise when into the pedal. The exhaust is also black where it is normally clear when in that RPM band when loaded. Otherwise idles great and no other symptoms. Seems to also be intermittant.Is this the symtom of a fuel filter just getting plugged at higher fuel flow?? Injector pump getting starved?bad Injector?valvetrain issue?Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/35911-mack-300-etaz-upper-rpm-exhaust-fluttering-noise/ Share on other sites More sharing options...
wheeler73 Posted May 31, 2014 Share Posted May 31, 2014 Black smoke means to much fuel or not enough air. Check for boost and exhaust leaks. Quote Link to comment https://www.bigmacktrucks.com/topic/35911-mack-300-etaz-upper-rpm-exhaust-fluttering-noise/#findComment-247430 Share on other sites More sharing options...
Art_H Posted May 31, 2014 Author Share Posted May 31, 2014 What about an injector having an issue and opening at lower pressure etc? Would that not cause black exhaust? Quote Link to comment https://www.bigmacktrucks.com/topic/35911-mack-300-etaz-upper-rpm-exhaust-fluttering-noise/#findComment-247463 Share on other sites More sharing options...
Art_H Posted May 31, 2014 Author Share Posted May 31, 2014 had alook this morn... turned out to be a leaking #6 exhaust manifold. Just a slight leak until the pressure climbed up. The valve cover gasket that leaks a little masked the telltale soot indicators.By the way, it seems difficult to seal these valve covers. New gasket and it still leaks. Heard you just have to get it on the 'sweet spot.'Thanks again. Quote Link to comment https://www.bigmacktrucks.com/topic/35911-mack-300-etaz-upper-rpm-exhaust-fluttering-noise/#findComment-247468 Share on other sites More sharing options...
wheeler73 Posted June 1, 2014 Share Posted June 1, 2014 Your right about the sweet spot. From what you were describing it sounded like an exhaust or boost leak. Glad you found it. Yes an injector can cause the issue but usually there is a miss fire. Quote Link to comment https://www.bigmacktrucks.com/topic/35911-mack-300-etaz-upper-rpm-exhaust-fluttering-noise/#findComment-247557 Share on other sites More sharing options...
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