Help needed on a 1998 750iL - M73 engine

[TxGR8White]

The CHECK ENGINE light was on, some rough running - pulled the codes and it indicated among other things BANK 1 and 2 O2 sensor failure. Replaced all 4 with BOSCH OEM, as well as both ignition coils. Tried to start the car and it would start, run for about 3-5 seconds and die. Unplugging one of the coils (didn't matter which one), the car would at least continue to idle in LHM (it could also be driven). Plugged the second coil in and back to not running longer than 3-5 seconds.

I also replaced both MAFS with new units - same result.

New codes said SECONDARY IGNITION CIRCUIT - replaced both caps and rotors and still no change is the crappy running.

Hooked the car up to the GT1 diagnostic, and it won't read anything at this time. A standard OBD II reader comes back with only 1 code now: P0350 FAULTY IGNITION COIL/ MISFIRE. I have tried 2 sets of brand new BOSCH coils with the same results.

Can anyone help me here - at wits end. This car is a very large boat anchor at the moment - need to get it driving again.

Thanks in advance

[Shawnchim]

Check your Mass air flow...mine was idling rough and codes were coming up..so I changed it ,got party from draler...and everything worked fine ...car is designed to throw off multiple codes ,so you bring car in to get fixed right away..I'm about 12,000 into mine ,,but awesome car when it's running right .

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[TxGR8White]

MAFS are BRAND new...

[Miss BimmerLV]

Sounds Like You Have An Electrical Gremlin. There is Nothing WORSE, Than Electrical Problems on a 750! Start Checking Fuses......Upfront in The Engine Bay, And Again In The Rear Trunk...Doesnt Matter Which fuse you check.....Because you are going to Check ALLE of Them....THEN, If They are Alle Good.....Begin Buy Restoring he Battery....Making Sure it can Hold a VERY Good 12v Charge. Have It Tested at Auto Zone or Sumthing...And If THAT is Good, Proceed Te Replacing The Ignition Wires To BOTH Banks....(Zyl 1-6 / Zyl 7-12)....And If That STILL Doesnt Wok....Begin Looking Into The DMEs .....INSIDE The Elctrical Box. Check ALLE The Connections Inside. Look For Water Damage or RUSTED Pins of ANY Kind...MOLD or Moss Growing Inside The Electrical housings....ANYWHERE inside the box......And If THAT Doesnt Solve....Komme Back Hier...And We Will KONTINUE to werk at solving The Problem


You ALSO Need To Find Out, WHY, Gt1 is not being able to kommunikate with the car...That alone is a tell tell sign something is SEVERELY wrong......CHECK YOUR WIRE LOOM for any bends or breaks or ANYthing looks out of he Ordinary. Also....ANY Electrical conponent that is bad or rancid, ( That plugs into the wire loom ) Will send feedback into The Wire loom and Wreak HAVOC on The Electricals....And Also Cause the Gt1 Not to able to communicate with the car.....One Example of This.....If one or BOTH throttle bodies are bad....The Whole Freakin Electrical System will go nutso! ....Ask Me How I Know. They Dont Teach Ya That Typa Scheisse in BMW School

But What Do I Know....I Just Help Women Get Their Sexy Back <3

[Ogregev]

Sounds Like You Have An Electrical Gremlin. There is Nothing WORSE, Than Electrical Problems on a 750! Start Checking Fuses......Upfront in The Engine Bay, And Again In The Rear Trunk...Doesnt Matter Which fuse you check.....Because you are going to Check ALLE of Them....THEN, If They are Alle Good.....Begin Buy Restoring he Battery....Making Sure it can Hold a VERY Good 12v Charge. Have It Tested at Auto Zone or Sumthing...And If THAT is Good, Proceed Te Replacing The Ignition Wires To BOTH Banks....(Zyl 1-6 / Zyl 7-12)....And If That STILL Doesnt Wok....Begin Looking Into The DMEs .....INSIDE The Elctrical Box. Check ALLE The Connections Inside. Look For Water Damage or RUSTED Pins of ANY Kind..ANYWHERE inside the box......And If THAT Doesnt Solve....Komme Back Hier...And We Will KONTINUE to werk at solving The Problem


You ALSO Need To Find Out, WHY, Gt1 is not being able to kommunikate with the car...That alone is a tell tell sign something is SEVERELY wrong......CHECK YOUR WIRE LOOM for any bends or breaks or ANYthing looks out of he Ordinary. Also....ANY Electrical conponent that is bad or rancid, ( That plugs into the wire loom ) Will send feedback into The Wire loom and Wreak HAVOC on The Electricals....And Also Cause the Gt1 Not to able to communicate with the car.....One Example of This.....If one or BOTH throttle bodies are bad....The Whole Freakin Electrical System will go nutso! ....Ask Me How I Know. They Dont Teach Ya That Typa Scheisse in BMW School

But What Do I Know....I Just Help Women Get Their Sexy Back <3

I have a 740 and I had trouble with scanners that were plugged into the round connector not being able to talk to some of the car systems. It turned out that the socket had corrosion on some of the pins. After a good cleaning everything worked. I suspect it couldn't maintain a high enough bandwidth to handshake with some of the systems.

I'm not saying this is your problem, but it you might have a similar problem causing the communication failures, and it's easy to fix.


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