If its anything like the diesels the throttle linkages probably need lubricating inside the ball sockets and the little nubs they hook onto. Try lithium grease, assembly lube, or ATF... if you use the heavier greases like the first two don't overdo it, just a thin coating or you will have problems. ATF I never liked because it's too runny, messy and doesnt last long enough.

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1985 CA 300D Turbo , 213K mi