[Healeys] Austin Healey 100 Misfire Diagnosis.

[jomar healey]

 Pull the plugs just to be sure it's not isolate.  Maybe a bad plug wire? Anyway that's where I would start
Joe #923
    On Wednesday, September 28, 2022, 07:43:30 PM EDT, Roger Grace <roggrace at telus.net> wrote:  
 
 The real mystery is why did it stop after you refuelled ?Was there enough time for something hot to cool down - but that does not really explain theinitial missing when cold.Presume that you have given the cap and rotor a good visual ... tracking can have weird effects. 
Plug leads ?rg

On Wed, Sep 28, 2022 at 3:46 PM Michael Salter <michaelsalter at gmail.com> wrote:




This problem has plagued me for over 1000 miles.

Today I had to drive some 200 miles and this is how it went:

Starting from cold I experienced a persistent and irregular misfire.

Pulling the choke out made no perceivable difference.

Power was not much affected and the car cruised along wellin top overdrive with just regular periods of misfiring.

Climbing slopes really made no difference, even when fullthrottle was applied for 10 - 15 seconds.

Misfire continued for some 90 miles with no change when theengine was fully heated up.

I could really do nothing to influence the rate of themisfire although it did seem to be slightly less evident at low throttlesettings.

After 90 miles I stopped briefly to get fuel and uponstarting off it was quite evident that the misfire had disappeared almost completelyand remained that way for at least 80 miles after which it started to misfirejust a little as I came to the end of the trip.

 POSSIBLE CAUSES

1.     Plugs … not like a bad plug. The misfire seemsto be more than 1 cylinder and never came close to being the regular beat that 1plug misfiring produces. All the plugs have a healthy brown/ grey appearance.

2.     Coil …  Inmy experience coils are very reliable but when they do fail they tend to failas they warm up and the problem gets worse as the coil warms up

3.     Points … a possibility but the dwell is set atexactly 60 degrees and does not waver at all when the engine is running in theshop.

4.     Fuel pump … if the engine was starving for fuelbecause of a fuel supply issue caused by a blockage or failing pump the problemwould get worse when the demand for fuel increased, as in climbing a hill offull throttle. This was absolutely not the case.




Any ideas folks?




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