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Rare but persistent engine missing phenomenon

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slacsteve

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For four years my SU carbed 1098 66 Sprite has on rare occassions (every few months) while traveling at highway speed started missing badly and losing power. After 30 seconds of trying to keep it going I come to a stop - won't idle - and the restart it. Persistently it starts up, revs up, zooms off and doesn't show this behavior again for several months. Always at highway speed. This has been going on for 4 years. Any ideas?
 
Gunk in the carb, vapor lock, or vaccum in the fuel tank caused by a clogged breather hole in the fuel cap, or if an electric fuel pump stuck points?
 
Maybe a coil that is heating up and breaking down. I had this happen to me on a '65. Try letting it idle while you use a heat gun on the coil to see if it happens then.
Jeff
 
My sister had an old Datsun that had this problem. It was caused by trash in the gas tank. At highway speed, the fuel pump was moving enough product to suck a piece of garbage into the pick up. Turn the motor off, the piece of trash falls away from the pickup and everything works fine again.

Her solution: sell the car to some poor, unsuspecting, sucker.

morris
 
Dropping the gas tank is quite easy if you can get it up on a lift (or at least well off the ground). It shouldn't be hard to dump out the gas from the tank.
 
My gas tank even has a drain in the bottom, then they real easy to remove.
 
Gunk in the gas tank, an air leak at the nipples of the fuel pump, rusted up gas cap vent (always at highway speeds, try running with the cap off or slit the gasket on the cap.
sludge in the float bowls, or incorrectly set float using all the gas at speed.
 
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