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Registered
Join Date: Apr 2006
Location: Milwaukee, WI
Posts: 50
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'73.5T CIS idle sounds and stutter
Hello-
I have read alot of posts where the cis gurus can adjust their mixture just by listening to the idle. When my T idles I hear a sort of low pitched thumping that is sparratic. It's not very loud and most people wouldn't notice it. Kind of like I had the radio on in the car, and I can barely hear the bass outside. The idle is perfect and doesn't budge. The car drives awesome and the ignition and fuel systems all check out fine. The only other thing that I notice is a slight hesitation/stutter at around 2700-2800 rpms. It has had this forever. They only way I even know that the stutter is there, is because the gear ratio has you cruising in this rpm range at 30mph and 40mph. I do hear that bass thumping sound a little bit while driving in this rpm range. Maybe someone can help me iron out the last annoying thing to fix on this car. After this, I am golden until something breaks. Probably next summer. Thanks. - J Last edited by jcwolff; 08-07-2007 at 07:58 AM.. |
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08-07-2007, 07:46 AM
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Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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It didn't have the sound, but did have the hesitation on my 73.5 some time ago. Pull each injector and squirt into a glass jar. If you don't get a fine mist, clean that injector. For me, it's all good now...
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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08-07-2007, 08:02 AM
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Join Date: Apr 2006
Location: Milwaukee, WI
Posts: 50
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Thanks for the reply. I have had my injectors bench tested a couple of times, and it has made no difference to this particular problem. Interesting that you don't have that bass sound. Many people have told me that the sound is normal and not to worry about it.
Last edited by jcwolff; 08-07-2007 at 08:23 AM.. |
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08-07-2007, 08:19 AM
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Registered
Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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My hearing is not the best, I may have the noise?
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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08-07-2007, 08:32 AM
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Registered
Join Date: Feb 2001
Location: South of the Mason-Dixon Line
Posts: 3,722
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Thats weird! I have had my 73.5T for about eight years now and have experienced everything, but a "thumping" noise. That bump at 2700-2800 rpm can be a few things. Take a long screwdriver and while the engine is idling hold it to the engine at various locations and listen at the other end close to your ear to hear if anything internally is thumping around inside. Throwing out some wild guesses, sometimes the alternator bolts in the fan housing can become loose and your hearing the vibration from a bearing becoming slightly offset. Fan belt seated well and tighted to spec?
When I once was hitting a flat spot on the rpms as your experiencing I re-adjusted my points and that took care of the problem. Check your point gap, if your still running points. Are the ignition wires okay? No telltale cracks in the distrbutor cap? Rotor worn? The checklist can on and on you know until you pinpoint the problem with the flat spot in that rpm range. If it is not electrical, then with CIS is can be anything. I know I would right away add a longneck bottle of Chevron Techron for starters to clean up the injectors and lines to a half-tank of gas, inspect and re-set the point gap. Keep us posted........ Bob 73.5T Sepia of course 
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08-07-2007, 10:16 AM
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