I'm hoping someone can point me in the right direction to fix this so I can avoid giving more money to a shop..

I have a '90 740ti automatic that I just got back up and running after being in the shop for a cranking no-start. On the drive home it drove fine until it suddenly no longer wanted to go into 3rd gear. Once it reaches the point where it should normally shift it just stops accelerating. I don't want to push the car, but initially trying to accelerate to higher rpm would do nothing but make the turbo whine and push black smoke out of the exhaust. No additional forward movement, only engine revving. When letting off the gas and slowing down it will try to stall. It drives around seemingly fine through first and second gear. On start up it has a rough erratic idle and occasionally drops slightly or goes up to idling at 1000rpm for a few minutes until accelerating a little.

I've replaced the maf sensor, several hoses including turbo intake hose, both relays under good as well as fuel relay, crankshaft position sensor, spark plugs and wires, service belts.. The obd gave me a couple codes I can't recall exactly at the moment, but one had to do with running rich, and the other had something to do with the maf sens wiring.

Any help or advice is appreciated

 

black smoke? thats usually bad juju in the engine, as in bad rings, valves, basically worn out motor.

make sure the transmission throttle pressure cable is adjusted properly and freely comes out and retracts. there should be a small bit of slack with the throttle at idle, and when you fully depress the pedal, you should feel a 'notch' of resistance just before it goes to the floor from the kickdown gear. if thats all good, then its quite possible the transmission itself is failing. if the cable is stuck out fully extended and not retracting, well, you need a new cable.

 

Was this problem present BEFORE the car was in the shop? I'd look into what was done in the shop to solve the no start--your problems sound more engine than transmission. It could be something quite simple, like a switched ignition wire. Won't be the first time...

 

Oh boy.. it's only black smoke when I rev it to try to persuade it to go into 3rd. Also not sure if it having a 2 month old tank of gas could have anything to do with that. Probably not.
I did check to feel for the kickdown notch and it was there.
Would the bad rings and valves be something that a minimally experienced person like my self could attempt to replace? Or is that as complex as it sounds and not worth it to pay to fix? How can I check the condition of those?
Though if the transmission is going then nothing is worth it.

The problem was not present before it was in the shop. I was able to drive the car probably 40 miles home from another town after first purchasing it with no problems. Though after getting it home it developed the starting problems which according to the shop turned out to be due to loose wiring connections to the ecu and battery I believe. The shifter bushings were replaced as well if that could have caused anything. He replaced sparks plugs, fuel filter, crank pulley, and temp.gauge switch. And the battery.

 

a compression test would tell you what sort of shape your valves and rings are in.

its easier to swap the engine block and head with a good engine from a wrecked car than it is to do the full rebuild that rings and valves involves.

black smoke /could/ be the result of mixed up spark plug wire order, or the timing belt having slipped a tooth or two.

 

Just to update:
The shifting and powerloss problem was caused by the throttle body hose slipping off. Feeling pretty dumb for not noticing it until a couple weeks ago. Mechanic must not have tightened or put it on completely when looking at it.
I do appreciate all the help here though.

Anyway, that solved most of my problems. It drives fine now. I'm glad it was that simple.