Ed Smith (BEChr@compuserve.com) writes:
> After initial warm-up, no choke, the engine starts to miss randomly
at
> idle & can be induced to increase the frequency of random miss by
> “loading” the engine by climbing a hill or shifting to a higher gear at
> an inappropriate speed, (thus pulling down on the engine). SU carbs
> have been “re-built” with gasket kits. Pollution controls have been
> temporarily removed & ports sealed.
> 1976 TR-6, 41,000 miles
> new vacuum lines & flame arresters
> Crane Electronic Ignition
> Crane Coil
> New “Blue Standard” wires
> Bosch Platinum plugs
> New Rotor
> New Rotor Cap
>
> Troubleshooting:
>
> Incandescent Light connected to (+) side of the coil & observed
> while engine randomly misses. No blinking or reduction in intensity of
> the light bulb.
> Timing Light connected to each plug wire & miss occurs to on all
> plugs.
> Timing Light connected to “coil wire” & miss also occurs through coil
> wire (of course)
Ed:
Three things come to mind right off:
1) I think the Crane ignition and coil setup is designed for NO ballast
resister. I KNOW the one I am using in my '71 is designed that way. The '71
TR6 did not use a ballast resister, while the '76 did. If you have not
rewired the car to eliminate this resister, you can have just the symptoms
you write about. If this is the case, drop me an e-mail if you wish, and I
will provide instructions for removing the resister.
2) The plus side of the coil is wired directly to either the battery, via the
ignition switch, or to the ballast resister, if you have one. It is not
switched by the ignition system (whether points or electronic) The switching
is done on the ( - ) side of the coil. You will always have a steady voltage
at this terminal. This is a good place to check for a ballasr resister. With
the key on, but NOT in the start position, measure the voltage at the ( + )
coil terminal. If it is equal to the battery voltage, or very near, then you
don't have a resister; if it is less, on the order of 8 -10 volts, then you
do.
3) Since you can see the miss with the timing light, you have eliminated
every other possible cause of the miss except for the ignition components,
ie, it is not the carbs, fuel delivery system, etc.
Dan Masters,
Alcoa, TN
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