New distributor cap is buzzing
Thread Starter
Intermediate
Joined: Jan 2005
Posts: 46
Likes: 0
From: Woodstock Georgia
New distributor cap is buzzing
I replaced the plugs, wires cap and rotor on my 87 and the distributor is buzzing like the rotor is catching on something. I've taken it off and can't find anything wrong. The engine has a serious miss after 1700 RPM that wasn't there before. Any ideas?
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
There four screws that hold the black plastic cap to the aluminum distributor housing. The first thing I would check is to make sure the cap is tightened to the aluminum housing properly. Make sure the cap is properly down (on all four points) and not "cocked" on the housing. If this does not appear to be the case, something is rubbing somewhere. Remove the cap and look for any "rub" marks by the rotor on the inside of the distributor cap. Just some thoughts for you
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
There four screws that hold the black plastic cap to the aluminum distributor housing. The first thing I would check is to make sure the cap is tightened to the aluminum housing properly. Make sure the cap is properly down (on all four points) and not "cocked" on the housing.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Make sure the little SPRING is still on the carbon 'button' that transfers HV from the coil to the rotor button.
They LOVE to fall off while you're working on the cap.
It's so easy to lose them it's redicilous.
Make sure the carbon button is in there too. I've seen folks leave them out.
Another tip is to..... turn on your radio to AM and tune it down as low in frequency as it will go 520~540 kHz and listen for the 'buzzing' sound.
If you hear it then there is something definitely arcing in your ignition system and that's probably what you hear.
This works for bad plug wires also. Doesn't help you to FIND the problem, just helps to DIAGNOSE the problem.
They LOVE to fall off while you're working on the cap.
It's so easy to lose them it's redicilous.
Make sure the carbon button is in there too. I've seen folks leave them out.
Another tip is to..... turn on your radio to AM and tune it down as low in frequency as it will go 520~540 kHz and listen for the 'buzzing' sound.
If you hear it then there is something definitely arcing in your ignition system and that's probably what you hear.
This works for bad plug wires also. Doesn't help you to FIND the problem, just helps to DIAGNOSE the problem.
Thread Starter
Intermediate
Joined: Jan 2005
Posts: 46
Likes: 0
From: Woodstock Georgia
Yep!. I took it all apart and neglected to transfer the ground lug over to the new cap. Now it's quiet at least. It's late and will have to wait till tomorrow to fire it up and see if it's still missing. Thanks for all the help.
Le Mans Master
Joined: Feb 2005
Posts: 6,477
Likes: 565
From: Clearwater Florida
cap & rotor
Hey...I had an experience once where the coil mounting screws were a tad long and were long enough that two of them actually broke thru the cap just ever so slightly and caused some serious misfiring since they ground to the coil itself. That one was a real troubleshooting mindbender 
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