I have had a compression test done, I don't have the numbers in front of me but they were all in the mid to upper 300's with little difference between cylinders. The shop said that it was good and to validate the test, it started this winter below 0 F without a block heater.

Could there be anything to the injectors leaking between the injector halves?...just grasping at straws here.

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1987 300TDT ~264,000 miles