Recently, while driving along a nominally busy avenue with a regular interval of Stop Lights, my 280sl was held to 3rd gear (25 mph is where it consistently shifts into 4th). Along this stretch of road, if I needed to slow or coast, the engine seemed to lose power or even cutoff. But when I pushed the accelerator it would come back to life. If I came to a stop or a normal down shift occurred, it ran fine in 2nd or 1st. When I passed the congested part of town, and was able to run in 4th a just a little while, cruising in 3rd gear was back to normal smooth operation. The engine and injector pump were both rebuilt less than 10k miles ago. Maybe related: After receiving the rebuilt drivetrain, whenever I manually shifted into 3rd gear, I experienced a very similar issue. But with manually selecting 3rd, the engine behaved much worse. It seemed like it was being drowned in fuel. I would have to drive a mile or so to get the engine back to smooth running. Since then, I have consciously allowed the automatic transmission to do its own thing. The odd behavior I could just avoid is now something that makes town traffic something to consider.
Can anyone tell me what component needs attention? Is there a step in linkage adjustment that leads to behavior like this?