[Healeys] Missfire/"Puffing" Continuing

[PhilRitten at aol.com]

All,
 
I am still getting a "puffing" noise from my BN4/6 after I have driven  it a 
little. After warming it up, I take it up on the freeway a mile or  two, turn 
around and bring it home. After that, every fourth  or fifth sound out of the 
tail pipe is a "puffing" sound. Interestingly, the  idle is still smooth (no 
obvious missing). The only way you can tell there is a  problem is listening to 
the tail pipe.  BTW - when idling and warming up in  the garage there is a 
steady staccato sound from the tail pipe. 
 
I'm rather puzzled. I replaced the plugs/cap/rotor/wires and set the  timing 
around 15 BTDC. I looked under the hood at night (in the dark) to see if  
there was any shorting and didn't see anything. There doesn't seem to be the  same 
problem with the rotor rubbing on the cap that I had before. By the way, I  
have electronic ignition.
 
I'm wondering if it could be something like a bad coil or something that  
fails once it has warmed up.
 
Thank you all,
 
Phil



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