1987 300 TD, with 88K miles, has started to exhibit an elevated idle speed (approx. 1200 rpm), in neutral and in drive, at the end of non-stop 200 mile interstate drives. When allowed to cool overnight, the idle speed returns to normal and does not recur during city driving. With the exception of the elevated idle speed, the engine behaves flawlessly, with no other symptoms present. Any ideas as to the cause of the idle speed elevation?

Any ideas? Injection control unit?

Dealer won't look at the vehicle without the problem present and its difficult to do a 3 hour interstate drive just prior to taking it to the dealer.

Thanks.

I have an 87 300TD that was occasionally having a fast idle at infrequent intervals. I ran some diesel purge through the system and it seemed to take care of the problem.

Does your car have 88K original miles? If so, interested in selling it?

Henry

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