635 loses power when downshifting

1987 635 3.5. When down shift in to 3rd (going up a hill, etc.), engine sputters and no power until I back off the gas. The two cable linkage points to the carb appear not to be sticking when stationary, but can't tell when I'm on the road. Thanks.

I assume this is an automatic, also does it do this in 3rd only. What if you are in 2nd and floor it does it run fine?

Thanks GTO

Yes, 4-speed automatic. Problem only occurs when downshifting from 4-3. Typically its a hard downshift (floor-it going uphill). After its in 3rd, I can floor-it and downsift to second. Problem does not occur in 3-2-1 or Sport mode. There are two cable going to the carb. The one closest to the firewall was sticking. I WD40 the heck out of it, but problem still occurs.

DSHO

In "S" & "3-2-1" mode 4th (OD) is locked out, you only have 3 gears. When in "Direct shift" mode (3-2-1) if you leave shifter in "D" you are in 3rd, the trans will only go in whatever gear the shifter is in, even from a standstill. You said you have a carb?? No fuel injection? Are you referring to the throttle body? If you have a carb and you are losing power you may have a bad float in the carb. Worst case is the trans is hanging up between shifts, but that is the last scenario. How long have you had this car and have you owned any BMW's in the past. The reason I ask is with the transmission you have you ABSOULTELY cannot take the car from either Reverse or Drive and place into "park" or "neutral" and rev the engine. One of the clutch packs stays pressurized until you turn off the car first which has resulted in numerous trans failures. I'm not saying this is the problem but just want to let you know in case you are not aware. Let me know if this is FI or carb.

Thanks again GTO. I'm a rookie to the terms. It is FI, and what I called the carb is the Throttle Body. Understand that Sport and 3-2-1 by- passes the OD (4th). Didn't think it could be a trans problem. Thought it was in the throttle body. If I gently hit the gas in 4th, it will downshift to 3rd most of the time, no problem. If I punch it, 75% of time it stalls-out until I back off on the gas.

The drive-reverse, then to park-neutral and rev the engine is what I do to get the car out of the garage and warmed-up. Take it, this is not the thing to do. First time I heard of the clutch pack issue. I've changed my morning ritual. Thanks.

What happens at 45 mph when you floor it, also depressing the kick-down? Does it get up like a raped ape or feel sluggish.

At 45 on level ground (its a Colorado thing), its 50-50 whether it downshift to 3rd or stalls-out for a moment before downshifting to 3rd.
When I say stalls-out. Its as if the engine totally cuts out. Tac drops to near zero and I have to play with the gas to find the sweet spot where the engine comes back. Once in 3rd, depressing the kick-down makes it go like an ape. Tac @ 5K+ RPM. Problem is in that brief moment of down-shifting from 4th to 3rd.

At 45 MPH it should drop down to 3rd, when you depress the kickdown it should drop down to 2nd. I'm not to sure on the schematic of the throttle position sensor or (potienometer) that is under the large rubber boot on the throttle body, but you may want to check the resistance with a multi meter at the potienometer and make sure there is no "dead spot". Hook up the meter and you may need the key on and test for voltage rather than ohms, that I'm not sure on but call your local dealer and they can tell you how to test. Work the throttle slowly and see if the meter jumps at one point, this maybe the cause of the drop to idle. Before you check all that make sure there are no wires rubbing or grounding out anywhere under the hood, look anywhere a wire touches any metal.