E39 - BMW 2003 525i Sedan - Loss of Power

[brukwood]

Hi,

While driving around town running errands on a relatively warm day (80 degree weather day), decided to turn the A/C on. After driving for about 7 miles, stopped at a red light, noticed car started hesitating. When the light turned green, pressed on the gas to move, the engine just revved high, "no power". Car wouldn't move. With help from other motorists, managed to push car off the road into the parking lot. For the next 60 mins, I struggled with the car, after each start. Car would start, but struggled to stay alive. Engine would sputter, then die. Managed to get car home that evening without a tow truck, multiple start and stop.

Parked car for 2 weeks. Did nothing, changed nothing.

Started car after 2 weeks, roared to live like a lion.
Have been driving car for past 4 weeks now without any problem, but no A/C
Nervous if I turn A/C on, same "loss of power" will happen again.

In the past one (1) week, I have

DIY:
===
Changed the engine oil to Liqui-Moly 5W-40 and oil filter
Replaced the MAF Sensor

I know the "loss of power" problem is still there.

A.) What is going on when "loss of power" happens?
B.) What additional checks should be performed?

Thanks in advance.

[Dave Sal]

Could be your fuel pump intermittently failing. Also wondering if it's your transmission, based on your comment of "When the light turned green, pressed on the gas to move, the engine just revved high, "no power".
So the engine revved, but the car didn't move?

[edjack]

Read the codes. Report back.

[WBAD530i]

This sounds like the exact thing I experienced when the transmission oil pump bearing spun off. Revs up real good, but does not move.

[brukwood]

Could be your fuel pump intermittently failing. Also wondering if it's your transmission, based on your comment of "When the light turned green, pressed on the gas to move, the engine just revved high, "no power".
So the engine revved, but the car didn't move?

Hi Dave, I communicated this wrong. It happened again today, after changing the fuel sender (both tanks) and fuel pump. The engine did not rev at all, the car actually struggled. A lot has happened since my initial post:

AFTER WRITING POST:
==============
I pulled the codes ask you suggested.
I used a basic scanner from "Schwaben Scanner 14020SCH".


Here's what I got (that really mattered):


EE DME: Misfire, cylinder 1
EF DME: Misfire, cylinder 2
DF IKE: Tank Sensor 2 (without fuel pump)
90 IKE: Voltage suppl, terminal 15 faulty




AFTER READING CODES:
===============
Next day, today I cleared only the DME codes
I replaced both fuel sensors in tank 1 & 2; and fuel pump in tank 1.




AFTER REPLACING FUEL SENSORS:
======================
Decided to take car for test drive
Immediate improvement in Fuel gauge reading
Immediate response and performance from car, spirited driving no problem.




IT HAPPENED AGAIN:
==============
Feeling confident I had fixed the issue, I turned on the A/C
Drove to the pharmacy, to pick up my stuff (about 7 ~ 8 miles from home)
No prob
Turned off the car, went inside, came back out, 15 mins max.
Turned on the car, with A/C running and started heading home.
About 4 miles away from home, same thing happened again ... LOSS of POWER.

[djb2]

It's probably not the problem, but it will take only a minute: swap the fuel pump fuse (white 25 amp, position 22 in glove box). I had a fuse that cracked. The intermittent high-resistance contact made it very difficult to track down -- it sort-of worked, sometimes, and measured +12V with the connector unplugged.

A replacement fuse was the fix, with no recurrence.

[brukwood]

Thanks djb2, I will give that a try.

Thank you everyone for the responses, my sincere gratitude.

The car is running great now, but I still fear turning the A/C on.
I read out the fault codes again and there's only one fault that remains: "terminal R"

Like djb2 suggested, replace the fuses.
Thank you