Intermittent Loss of Power and Running Rough

[BMWJake]

Hello, I own a 1987 325e its an auto (with a manual swap ready to go next year) with the Motronic 1.0 system. I bought the car in May and spent the summer fixing it up to back to almost perfect running condition (bought the wrong odometer gears though kinda frustrating) When it runs great it is a fun car to drive but I have one intermittent issue that I am fully stumped on.

So it starts and runs fine but usually once its warm after maybe half an hour of driving sometimes longer (hour or two I drive 5 hours a few times a month) the car will all of a sudden loose power. This happens any time from driving down the highway at a constant speed to driving around in town. It will either go away on its own or I turn the car off and start it back up and the problem usually goes away.

To expand on what happens during the time of power loss, I noticed it will not rev past 3k no matter how hard you push it and it struggles on hills (pretty much to the floor regardless of hill size) I also noticed that the econometer is limited too and doesnt go over 15-18L/100km during this time. While stopped in drive or parked, during this period of time the car kinda chugs or stumbles and the rpms are much lower and it seems like the car is going to quit but never quite does. Although if I try and reverse during this time the car dies and I have to restart it. As a side note, since Ive had the car its never really liked reverse maybe that could be some indication of my problem? One more thing I noticed was at low speeds (10-20km/h) the car surges/lurches and there is usually a lot of clunking lol. Probably cause the tranny can't handle the weird surging.

Sorry for the long paragragh but I want to be as specific as I can be. It sounds like it could be something transmission related but I dont really think thats the whole problem. As I stated earlier, I will have a 260 ready to go for next year but I dont want to install it and be disappointed next year when the problem continues.

Maybe its more obvious then it seems but I am stumped and would like a second opinion. Full parts replaced engine related are: spark plugs, spark plug wires, distributor cap and rotor, O2 Sensor, ICV and Idle Control Module, inline fuel pump, fuel filter and FPR. I have done the electrical tests on most of the components and everything appears to be fine. I plan on turboing it at some point but that probably wont be for a couple years and I'd like to enjoy it for what it is now.

Thanks for the help and sorry if the spelling and gramar is rough It has got me up late thinking about it.
Jake

[tomstin]

Have you pulled the in tank fuel pump and checked for debris in the tank? The junk can clog the in tank pump pick up sock and once the car sits it drops off only to get sucked up again. More often with the tank low.

[BMWJake]

Have you pulled the in tank fuel pump and checked for debris in the tank? The junk can clog the in tank pump pick up sock and once the car sits it drops off only to get sucked up again. More often with the tank low.

I checked it a while ago the tank was clean not a spot of rust and looked debris free but I did find part of a twig in there haha really weird! It was clear after that and running good. Never had issues with power loss with a lower fuel tank level.

[325e '87]

I could be wrong, but I believe the ignition coil can go weak once it’s hot under the hood. It’s also possible that the O2 sensor and crank position sensors can be effected by heat when they are going bad.

What makes a hot engine unresponsive? If it’s not fuel then it’s probably electrical? I’m not sure but just trying to narrow it down.

[BMWJake]

I could be wrong, but I believe the ignition coil can go weak once itÂ’s hot under the hood. ItÂ’s also possible that the O2 sensor and crank position sensors can be effected by heat when they are going bad.

What makes a hot engine unresponsive? If itÂ’s not fuel then itÂ’s probably electrical? IÂ’m not sure but just trying to narrow it down.

Yeah I am thinking electrical too, ignition coil is interesting and good to know I wondered about it being faulty I checked the coil ohms a while ago and one of the values might have been a bit off. It could have gotten worse when heated up since my problem is only showing up when warm.

O2 sensor is new. I just aquired a manual swap today and it came with 2 new crank position sensors so Ill try swaping them out before I try the coil.

I think Ill order a new ignition coil anyways Im thinking maybe more the coil now for sure cause sometimes I have trouble starting it when its warm as well. Thanks for the info.