First post on here, and I'm puzzled by this one. '93 400E with nearly 200k miles on it now. Have had the car for about a year now, gradually going through maintenance items as time and budget allow, trying to learn and correct its faults and quirks. Here's the basics of it - let's say I've been using it as a daily for a week or so. It will be running fantastic - engine is butter smooth, barely know it's running at idle, no squeaks or rattles, shifts well, propels you forward on that never-ending wave of torque. It's wonderful.
Let it sit for 48-72 hours - starts right up, idles great. But once you're doing like 40mph and you give it some gas, it bogs down. Gas pedal can be floored and it just sits there at like 1500rpm, ever so gradually climbing to 1600. Manually downshift it to 3rd, it improves, but there's still a bit of a shudder. After maybe 20 miles and/or 20 minutes, the problem is completely fixed. Back to its old self. You can actually feel it improving as the minutes tick away.
Let it sit for say 5 days, and it still starts right up. But now it hunts at idle. It might stall at a red light. It will bog leaving an intersection, even if shifted into 3rd or even 2nd. 40mph to 60mph is glacial. This time it takes about 30 miles/minutes to fix itself. But it again returns to its old, wonderful self. If you literally drove it everyday, I don't think you'd know this problem even existed.
I changed the auto trans filter and fluid right after I bought the car (about 8k ago) but that didn't make a noticeable difference. It has a very slight trans leak. A few drops over the course of a week.
Just yesterday I drove it for the first time in a week as I was away, so I tried to pay extra attention. It stalled a couple of times. No power. Bog slow. I'm open to non-trans related issues, but yesterday it shuddered a bit when put in either R or D while stopped. Put it back in N and it goes back to super-smooth, though with some hunting. That suggests to me its trans-related, but I defer to the wisdom on this board.
I can't imagine anything involving electronics or cables would behave like this. I will freely admit I really have no clue how autos work. I keep an eye on the fluid level, but if it was low, I don't see how it would fix itself. The only explanation I can conjure up is that somehow air is working its way into the trans due to the leak, and the longer it sits, the more air gets in. Once you start driving it, it will be terrible until it gradually self-purges the air and then all is well again. But that's just my half-baked theory, unimpeded by actual knowledge!
I searched but didn't seem to find any posts with this exact issue. It does not seem to matter if its spent its week outside, or in a dry garage.
Thoughts? The car is incredible when at 100%. I'd like to see if I can keep it at 100% more often. As it is, it forces me to drive it often, which I'll admit isn't really a bad thing.
Thanks for any suggestions.