This post will be a bit long I apologize.

I'm Jesse, and I recently purchased an 05 525i with some transmission issues and other miscellaneous problems in the hopes of flipping it. I quite literally just got the car 2 days ago and I haven't had the chance to scanned for codes; I will update the post probably this weekend after I do. Hoping to get some advice to point me in the right direction.

For starters not sure if it's in a limp mode I'm new to the BMW platform, this is my first time working on one. The car parks, reverse's and when you put it in drive it only goes into 4th gear and wont shift, like it's in overdrive, even in manual mode you can't shift it just says m4. the previous owner's son had put a mechatronic unit from a 6hp21 trans (the one in my car is a 6hp19) but he said it was having the same issue before he switched it out so probably isn't just the mechatronic (I think it's very likely this could be the issue so I'm not counting it out yet), he also said he would reset the system, not sure what that means but the car would work fine for a short period of time and just go back to the limp mode. He was very high when I purchased the vehicle, and he gave me the 6hp21 transmission the mechatronic unit in my car was attached to. The trans has 80k miles and work's fine, he says his son has a 2010 528i that he manual swapped and no longer had use for the automatic trans.

Also, the rpms are very jumpy, the car sounds fine like the engine isn't jumping but, in the rpm, meter would be jumpy and would just go to 0 out of nowhere from like .1 seconds. When the car was cold it idled complete fine but after I drove it home and tried turning on the car it wouldn't want to start, I freaked the fuck out and thought I just got scammed by a crack head. It took about 4 cycles of crank no start to get it to start with the gas pedal floored; after it stared it had a very rough idle and this time the rpm was jumpy because the engine was actually jumpy, I also got a message saying low oil pressure. The next morning, I tried turning on the car and it started up just fine and after I drove it around for a while I turned off the car and tried turning it on and same thing crank no start and rough idle. so obviously it only happens when the car is hot.

I was already thinking of doing an oil change, but I knew I had to after I saw inside the car there was a bottle of Oreilleys cheapest oil which wasn't full synthetic, I'm also thinking of testing the o2 sensors because I got message saying more emissions and white smoke was coming out of the exhaust. I'm going to replace the crank and cam shaft sensors just as a precaution; I will also be changing the oil pressure senor.

Main questions

• Could I swap the 6hp 21 transmission into my 05 525i that has the m54 engine and 6hp19 trans. I need it to work fine as in no codes and runs prefect.
• what's up with the transmission I'm guessing that it's probably the torque converter but just looking to see if anyone's gone through the same thing maybe it's a smaller issue?

-what's up with the car not wanting to start right after it gets hot.

-what's up with the jumpy rpms and it going to 0

• any thoughts on the low oil pressure confused because the engine is super smooth when cold.

(Side note now that I think about it the rpms only started being jumpy after I drove it for a while so maybe it's only jumpy when it's hot? I didn't notice the car moving/jumping though when I was driving it maybe I hadn't noticed because well it is a very minor jumpy feeling)

the vin is WBANA53505B861274 if that helps

also, I got the car for 700 with 250k miles am I cooked? actually tho everything else works, ac is ice cold and cosmetically it's in great shape no dents and paint is perfect.

 

You're definitely not going to flip the car with that many issues. You're looking at around $1500 low end if you're doing everything yourself to get it back to where it needs to be. I would first start by pulling the codes. If you have the original mechatronic I would put it back in as the valve body probably just needed to be serviced as in remanufactured or new solenoids put in. That runs about $800 sending it off or $300 for solenoids. Next you'll need to replace the crankcase hoses and vent valve. I'm sure you have vacuum leaks from the hoses be cracked. I wouldn't mess with sensors until then. If you replace the sensors ensure they are at least OEM. BMWs don't like aftermarket parts that make it run.

You can swap anything in a BMW if you are coding savvy. If you don't know how to code keep the transmission original and fix it. Also perform a smoke test because I'm sure you have multiple leaks.