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MG MGA - Varying Idle-Update

Just to bring closure to the topic. The answer appears to have been the ignition coil.

I did a warm up test, measuring the heat, oil pressure and rpm's over 25 minutes of idle. With the old coil max rpm was 950, after about 23 minutes the rpm dropped 50-75 rpm, but became "wavery".

New coil max rpm was 1015 after about 20 minutes the rpm dropped maybe 40 rpm, but was much more steady.

I took my normal drive to work today and after the typical 10 minutes of highway driving and coming to a light the idle remained solid.

I can only assume a weakening spark was effecting the explosion progression.
T McCarthy

i would be interested to know what model the old coil was and what you replaced it with.
thanks
lee
lee najman

Lee,

The old coil had absolutely no markings on it, other than a - and + on the terminals, which would suggest it was manufactured some time in last 20 years.

It was on the car when I bought it.

I replaced it with a pertronix product for $32.00. Well worth it.
T McCarthy

This thread was discussed between 12/05/2009 and 15/05/2009

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.