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Discussion Topic:
Miss idle
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silverchief |
08-08-2017 @ 1:26 PM
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Senior
Posts: 524
Joined: Oct 2009
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My stock 46 starts easily, but has suddenly developed a rough miss at idle. As late at this morning, it was smooth as glass at 500 rpm. First thing I did was pull all plugs, although done recently. Each was clean and in fine shape. Each plug wire shows a strong blue spark. Opened distributor cap. Everything is in nice condition and where it belongs. Slight pull on accelerator rod to increase rpm does not help. Can't be bad gas, I've used about 5 gals with no problem. Removed air cleaner and the choke plate is dead center. Last thing I did was this morning. Replaced a short piece of fuel hose in front of electric fuel pump. It was a little too short, allowing the pump to slide forward in it's holder. Don't see a connection there as there are no leaks and the engine is receiving fuel to start easily and accelerate without hesitation. Not sure what to look at next.
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pauls39coupe |
08-08-2017 @ 7:09 PM
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Member
Posts: 205
Joined: Jul 2014
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Does this miss occur with the engine cold or after it warms up? Have you tried adjusting the idle jets? If so , did it make any difference? There may be dirt in the idle circuit. Using a vacuum gage should help find your problem. I would look for a vacuum leak first, perhaps in the wiper hose or wiper itself. Try plugging the wiper connection to see if that makes an improvement. If it only acts up when warm you may have a bad condenser. Please let us know what you find. Paul
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silverchief |
08-09-2017 @ 10:31 AM
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Senior
Posts: 524
Joined: Oct 2009
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Thanks Paul, The rough idle occurs at operating temp. Forgot all about that magical tool - the vacuum gage. Will do that first thing. Also will check wiper hose and any other possible vacuum leak I can think of. I'll let you know what happens.
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silverchief |
08-09-2017 @ 2:48 PM
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Senior
Posts: 524
Joined: Oct 2009
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The vacuum gauge showed a problem with ignition timing. I checked it and it was off but only by a very small margin. In order to move the distributor I had to disconnect the vacuum line, and did so at the carb and distributor, to make sure it was plenty loose so I would not cross thread the connectors at either end. Neither was obviously loose. Later I replaced them just finger tight, and no sign of improvement in the rough idle. I planned to do a compression check tomorrow. Just before putting the tools away, I tightened both connectors as the last thing to be done. Started it up to pull into he garage, and every sign of a rough idle was gone. Set the idle rpm at 500 - smooth as glass. I guess the lesson is ........double check the most obvious simple things first, like a vacuum advance line that had over time, loosened just enough to cause a problem. Thanks for your help.
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pauls39coupe |
08-09-2017 @ 6:23 PM
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Member
Posts: 205
Joined: Jul 2014
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Thanks for letting us know the result. I'm glad you got the problem solved. Paul
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