E39 help, SOS. Losing power. (Lengthy read)

[Santiagonj]

Hey all

I have a 2002 530i that keeps losing power. I was able to clear the codes I had:p2098, p1085, p0171, p1771. Which was causing rough idling, misfiring, difficulty accelerating and stalling; occasionally the battery sign would come on to which I would foolishly accelerate it “away,” it’s to the point where that no longer does it (obv not a fix).

I’ve changed spark plugs, air/oil filters, fuel injectors, o2 sensors, MAF sensor, crank shaft and cam shaft position sensors, disa valve, fuel pump &relay. Since then the rough idling has let up significantly, no harsh shaking, the car’s initial warm up isn’t as shaky or jumpy from misfiring.



Some background info: I’ve had the car for a little over a year and the battery sign has always randomly popped up and as mentioned before, I’d foolishly accelerate it “away,” even after changing the battery.
I also had a bad power steering leak for quite some time which would be positioned almost right above the alternator.

I changed the DISA Valve today, and the engine light disappeared. literally went about 4 miles in a residential zone and lost power while in park.
Engine light BACK ON.
No noise, just a bit of shaking. Car refused to start there after. Given previous experiences it most likely will in the morning. Temperamental, much? Ughh

In terms of the power outage, might it be the alternator? If not, then what? SOS Please help.
I haven’t been able to take any readings either.

ALSOOO, what are the chances that a fuel pump isn’t sitting correctly? Better yet why do I have to switch my key to position 1, and allow the fuel gauge to rise before switching the key on? If not the car cranks and struggles to start. It wasn’t something I experienced until after replacing the pump.

If you’ve read this far, I APPRECIATE U.

Plz n thnx you

[PostChris909]

As for that battery problem, I'd check to make sure the ground cable that conects to the passenger side motor mount bracket is tightly secured. It is the only ground cable for the motor. One time i did a replacement motor mount and didn't lock up the cable and it also cause my motor to lose power at random or maybe even a cause for a misfire but i doubt it. You said rough idles but didn't mention tackling you ICV. If i were you I'd pull that out and make sure its clean or at least functioning. I once had a crappy throttlebody gasket that gave me misfires and I also lost my mind trying to figure out what it could have possibly been after replacing all spark plugs, all new CCV kit, new intake boots, valve cover gasket, MAF, and fuel filter.

On the other hand though, I have also experienced loss of power at random due to a failing fuel pump. I would be driving on the freeway at 70mph and all of a sudden my speed would drop like crazy as if my motor shut off instantly. It would stumbl while it lost power than it would spring back up again a few seconds later. Pretty scary to deal with multiple times.

With all that you have replaced have you considered getting it check out by a bmw oriented mechanic/tech? I don't mean the "stealership" but a reputable european mechanic. With all the money you've put into it, it wouldn't hurt to have it professionally checked out (that is if you aren't a professional yourself). Also a compression test wouldn't hurt at all, might even really help.

Besides all that give detail for detail on every little thing that happens when it loses power. Any lights going dim? Or ac blowing lightly, etc

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[PostChris909]

Also if you have a multimeter it'd be a good step to take it around to various suspected eletrical points/grounds in your car so you could at least rule out voltage issues. I believe you are supposed to have at least 12.40v for the vehicle to run properly, others may say more. If you are around 12.00-12.20v you ought to get your battery charged or replaced. If you find yourself getting a battery every year, your alternator just might be a suspect! I'd put the voltage of the alternator on priority if so

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[geargrinder]

changed spark plugs, air/oil filters, fuel injectors, o2 sensors, MAF sensor, crank shaft and cam shaft position sensors, disa valve, fuel pump &relay.
I changed the DISA Valve today

Attention Lieutenant Nutbuster!!!! Load up the Parts Cannon and FIRE AT WILL!!!



Jokes aside...

I'll second checking grounds and voltage levels.

Any water ever in the car? There's the passenger footwell swimming pool corrosion problem that can cause all kinda mystery voltage problems. Bad ignition switches too, although they tend to manifest other weirdo electrical symptoms (seconding PostChris again).

Also: Check codes with a proper BMW_compatible scanner, not a lousy pee-pee code scanner if at all possible. The info may be more specific/correct/complete.

[edjack]

Outside chance that the brushes in the alt are worn down, such that they lose contact with the slip rings. That could account for the randomness.

Quick check: Rig a voltmeter to the ciggy lighter socket, and watch it when it loses power. A sudden drop in voltage from 14 to 12 is a clue that the alt is janky.

[VormDK]

Have you changed the fuel filter?
Some of the symptoms you have could be caused by a clogged fuel filter...

It could also be a loose voltage supply pin in the ECU.

I don't see how the alternator could cause this - the battery (if healthy) should hold the voltage above 12v in all non-cranking conditions. And the ECU will run the engine just fine down to around 10 volt.

[geargrinder]

And the ECU will run the engine just fine down to around 10 volt.

I would not agree with this. IME you'll get some weird operating symptoms well before 10V.

[JimLev]

And the ECU will run the engine just fine down to around 10 volt.

I agree with GG.
When my alternator crapped out I monitored the voltage in the cluster. Around 11.2-11.3 volts the engine shut down.

[MIKYZZ4]

It seems to me that your problems may be related to the large amount of parts replaced.
Either there are bad connections to parts installed, or during the installation something adjacent was disturbed.

EVEN quite possibly the actual parts installed may be at fault. Rule of thumb - ONLY BMW OE or OEM replacements,
for ANY and ALL BMW sensors or critical electronic parts. Unless you enjoy chasing electrical gremlins or electronic anomalies.

I would go over all your work, confirming clean snug connections, followed by clearing all codes.
Perform new scan, preferably with a BMW specific scantool/software, that can communicate with all BMW modules.

Post back with results.

[computiNATEor]

I agree with GG.
When my alternator crapped out I monitored the voltage in the cluster. Around 11.2-11.3 volts the engine shut down.

Yep, and long, long before then the trans went into limp mode, followed by the ABS trifecta.