88 750il - LIMP Home - WHY?

[EWBankston]

My 750iL has been in limp home mode for several weeks now. My fault
reader says "emission (Lambda) controls." So, I changed both O2
sensors -- didn't help. Took it to dealership which identified faults
initiated by O2 sensor on passenger's side -- changed it again, did
not help. Identified fault initiated by driver's side mass air flow,
so ordered one and installed ($400.00), but that did no good, so
changed it to passenger side with no beneficial effect. Can't find
solution in manual. Can someone please help? Anything at all?
thanks, eddie b.

 

[carfix]

my 750 had a problem with failsafe mode ... the shop just fixed it... mine would intermitantly go in failsafe mode... there are 2 modes... the other is limp... failsafe is where it runs fine other than it won't rev up past about 2000 rpm... limp mode is where 1 bank shuts down... the trouble with mine which is really common is a broken wire in the wiring harness in the engine bay.... the heat bakes the insulation and it cracks and breaks the wire.... the way they finally found the problem was to test all the pin voltages at the computers... mine actually had 2 bad wires.... i'm going to pick the car up tomorrow.... it only took 6 weeks to find and fix the problem..... the servicee manual says that when you get false trouble codes like you're getting, check for broken wires.... i also talked to a couple other bmw and mercedes techs abd they all said the same thing... probably a broken wire in the harness.... the fix is after determining which wire(s) is bad, replace the wire or the harness with a new one.... used ones are not really an option due to the fact that they all get brittle... good luck, john
ps... try wiggling the harness that crosses behind the motor and see if it makes any difference.
i was getting check control unit message, which means the control unit is bad, which is wasn't....

 

[FrankieFigs]

Only 6 weeks in the shop? "Only"? That is sad. Was it the dealer?

 

[carfix]

the time frame was ok frankie.... i told them when i brought it in that it wasn't a priority fix..... i have other cars to drive.... they also cut me a break on the labor..... i told the service advisor that they could use it for filler work..... i just wasn't expecting a month and a half.... oh well... if it's fixed, i'm happy..... they only charged me $500 to fix it.... he said they had logged almost 20 hours on it... john

 

[FrankieFigs]

Which wire was broken? Was it one that went to a mass airflow sensor over the air filter? Right or left side?

 

[carfix]

not sure which wire.... they said it was a wire that went to one of the dk motors and there was another that went to the dash.... i know my eml light did not work before and it comes on now when i start the motor..... I LOVE MY CAR..... john