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Thread: 91 Running rich- I'm stumped...

  1. #1
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    91 Running rich- I'm stumped...

    Hello everyone, I'm having some problems with my 91. I fired it up a couple of days ago and it smelled very rich, idled unevenly, and had no power ( difficult to get 60 mph, sluggish to rev past 2500 in N)) After two days of poking around I'm no closer to a solution.

    Here's what the symptoms are:

    * Bank 1 (1-6) runs rich plugs sooty black (not wet)
    * Idles unevenly ( not shaking, but not smooth)
    * No power / slow to rev past 2500 (in N)
    * CEL light @ idle, goes out when reved
    * Tach shows low @ idle (100rpm?!)
    * Peak tool shows code C9, Lambda on bank 1 only, no other codes. (my stomp-test has not worked for a long time)

    Here's what I've done:

    *Vacuum readings (1-6=14.5) (7-12=17)
    *Pulled plugs (1-6 sooty, 7-12 clean)
    *Tested spark-both sides good
    *Compression check (all cyl 165-175psi)
    *Battery 14.8v ( stays on bat tender)
    *Disconnected bat.s & re-test-no change(vac & code)
    *Swapped MAFs - no change( vac & code)
    *Disconnected O2 sensors to run default map-no change (vacuum lower on both banks, still slow to rev)
    *Swapped FPRs-no change (vac and code)
    *Swapped DMEs-No Change(vac and code)
    *Tested IAT sensors @ DME plugs & @ sensor ( #1 1.706 Cold / 0.784 Hot; #2 1.690 Cold / 0.762 Hot)
    *Tested DME H2o sensor @ DME plug and @ sensor #1 1.490 Cold / 0.326 Hot; #2 1.445 Cold / 0.334 Hot)).
    *Both DKs buzz @ KO/EO
    *EML light on for ~2sec @initial key on.
    *Pushed down / pulled up on I.M. - no change in vac reading.

    This seems to be a fueling problem (?), not an ignition/spark problem, and something that affects all the cylinders on bank 1 eaqualy.

    I woiuld be very gratefull for any suggestions on what to try next.


    Regards,
    M.R.
    Last edited by M.Rad.; 09-13-2012 at 10:56 PM.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  2. #2
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    DK's need refurbishing?
    91 850 (Panzer), 2012 Mini Cooper Countryman (WifeMobile) www.wuffer.ca


  3. #3
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    Hi Wuffer! I re-furbed the DKs myself (a couple of years ago now) and things looked good inside including the carbon tracks. I cleaned and re-greased them and everything worked well up until a couple of days ago, and I have only about 1500 miles on them. They both "Buzz" with the ign. on. Tomorrow I will swap them side-to side and see if there is any change.

    Is there anything in particular I should watch for when I have them off??


    Regards,
    M.R.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  4. #4
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    Quote Originally Posted by M.Rad. View Post
    * Peak tool shows code C9, Lambda on bank 1 only, no other codes....

    ...*Disconnected O2 sensors to run default map-no change (vacuum lower on both banks, still slow to rev)
    Not sure what the "default Map" is, but have you checked each O2 sensor? Try swapping them and see if the Peak code goes to bank 2.

    Oxford Green Metallic, Parchment leather, 854 badge, EDC stock struts, M-Sport springs, 3.91 LSD, CSI rear sway, 18" M-Pars, M-Sport wheel w/flappy paddles, CD-43 head unit, Strong Strut brace, Euro FTPs, CSI rear defuser
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  5. #5
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    smc850ci-I tried swapping the O2 sensor connectors just for grins, but there was no change. ( I am sure of the positioning because I did a pin-out from the sensor harness to the DME harness last year).

    From what I understand, there is a default map for the engine to run on if the O2 sensors fail. In my case, the vacuum readings were still lower on the #1 (pas. side) bank, which leads me to believe that the initial problem did not change.

    Regards,
    M.R.
    Last edited by M.Rad.; 09-13-2012 at 08:32 PM.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  6. #6
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    Try your crank positions
    You cant swap them make sure thier is no dirt
    Or grease on them and they should be gaped at 1 milimeter from the teath on the counter ballance thier is a testing procedure with ohm meter dont remember what the values were the procedure and values are in the repair man
    You may also want to look at you fuel pressure regulators.
    1991 Racing Dynamics K55 Sport Coupe Six Speed Original Owner 18,600 Miles
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  7. #7
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    E31PARTS- I swapped the FPRs side-to-side with no apparent effect (post 1) the vacuum reading was still lower on bank-1. I applied vacuum to the fpr.s with a hand vac. pump, and they held steady. O-rings all good, etc. Is there any other test to perform on the FPRs?

    As for the CPS sensors, I believe (although I could be wrong...) that it would shut the bank down entirely if not functioning. I did make sure they were properly seated.

    Keep 'em coming, guys- I appreciate all of them.

    Regards,
    M.R.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  8. #8
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    I just chased down the same crap - turned out to be the DME temp sensor on the water coolant crossover pipe (the one with 3 pins on it). The sensor was bad and was telling the DME's that the temp was -49 degrees C outside. This caused a super rich condition to where the plugs actually stayed wet and the idle was the worst I have ever heard on a car.
    '93 850Ci - Mineralweiß Metallic

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  9. #9
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    Quote Originally Posted by TxGR8White View Post
    I just chased down the same crap - turned out to be the DME temp sensor on the water coolant crossover pipe (the one with 3 pins on it). The sensor was bad and was telling the DME's that the temp was -49 degrees C outside. This caused a super rich condition to where the plugs actually stayed wet and the idle was the worst I have ever heard on a car.
    This was my first thought. Especially since it is doing it on the default map too.
    Don't trust your multimeter on these, just replace all the sensors back there.

  10. #10
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    My car had a problem just like the it went into LHM (limp home mode), one of my MAF and o2 sensors needed to be changed

  11. #11
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    Hi Steffen- that was one of the sensors I checked today.

    I checked IAT both at the sensor and through the harness at pins #43 DME1 & 78 DME1 &2 and got 1.706 / 1.690 cold .784 / .762 hot the values when hot.

    DME 1&2 H2O was 1.490 / 1.445 K ohm cold .326 / .334 Kohm hot. These are within the parameters listed.

    Like I say, I'm stumped although I'm kinda leaning toward FPR, but how to test them accurately? Any other ideas?


    Cartoonz- I'll replace parts as a last resort, but I hate just throwing money / parts at it blindly. Why do you say not to trust the multimeter? The readings are within parameters, and the resistance decreases as temp rises, as it's supposed to. Besides, it gives me the willies to think of trying to replace those sensors back there!


    Regards
    M.R.
    Last edited by M.Rad.; 09-13-2012 at 11:01 PM.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  12. #12
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    Quote Originally Posted by M.Rad.
    E31PARTS- I swapped the FPRs side-to-side with no apparent effect (post 1) the vacuum reading was still lower on bank-1. I applied vacuum to the fpr.s with a hand vac. pump, and they held steady. O-rings all good, etc. Is there any other test to perform on the FPRs?

    As for the CPS sensors, I believe (although I could be wrong...) that it would shut the bank down entirely if not functioning. I did make sure they were properly seated.

    Keep 'em coming, guys- I appreciate all of them.

    Regards,
    M.R.
    It will not totally fail
    Went throught this with friends car you check the procedure and test them as part of your trouble shooting
    1991 Racing Dynamics K55 Sport Coupe Six Speed Original Owner 18,600 Miles
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  13. #13
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    Quote Originally Posted by M.Rad. View Post
    Hi Steffen- that was one of the sensors I checked today.

    I checked IAT both at the sensor and through the harness at pins #43 DME1 & 78 DME1 &2 and got 1.706 / 1.690 cold .784 / .762 hot the values when hot.

    DME 1&2 H2O was 1.490 / 1.445 K ohm cold .326 / .334 Kohm hot. These are within the parameters listed.

    Like I say, I'm stumped although I'm kinda leaning toward FPR, but how to test them accurately? Any other ideas?

    Regards
    M.R.
    Again, I'd not be so quick to presume anything as far as those sensors go. I've had several "test good", just as yours might, but they still end up being the problem.

    In "fixed map mode", there are really just a few things that can be causing you to over fuel.
    1. FPR's or major obstruction in return line
    or...
    Something is telling the ECU to over fuel it. There are not too many things that do that, and the CPS sensors are not one of them... those pesky temp sensors definitely are though.

    You could swap the DK's to rule out any hanky panky there...
    You've already swapped the ECU's, so that's ruled out.
    Last edited by cartoonz; 09-13-2012 at 11:07 PM.

  14. #14
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    Yeah, tomorrow I'll try the DK swap, just to see. If that doesn't get me anywhere, I suppose I'll get a temp sensor. I'd like to hold off on getting a FPR since theyre rather expensive x2.

    I suppose I could do a IAT sensor swap also just to see if it switches sides, since those aren't too difficult.

    BTW, does the EML temp sensor influence the mixture as well? I didn't check that one.

    It's off to sleep for now. I've had about all the exhaust I can stand for one day...

    Regards,
    M.R.

    Quick update-
    I swapped the DKs side-to-side but got nowhere. Still running rich, still has Lambda code for bank 1, still 2" less vacuum on bank 1.

    Since the general concensus is that the DME temp sender may be bad, I'll order the part.

    Does anyone have any other suggestions on what to test while waiting for the sender?

    Regards,
    M.R.
    Last edited by M.Rad.; 09-14-2012 at 04:18 PM. Reason: Automerged Doublepost
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  15. #15
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    Quote Originally Posted by cartoonz

    Again, I'd not be so quick to presume anything as far as those sensors go. I've had several "test good", just as yours might, but they still end up being the problem.

    In "fixed map mode", there are really just a few things that can be causing you to over fuel.
    1. FPR's or major obstruction in return line
    or...
    Something is telling the ECU to over fuel it. There are not too many things that do that, and the CPS sensors are not one of them... those pesky temp sensors definitely are though.

    You could swap the DK's to rule out any hanky panky there...
    You've already swapped the ECU's, so that's ruled out.
    I am not saying That the cps is definitvly the problem its a fact that a failing one can and will cause one side to run rich. all these sensors are all tied into ignition and fuel one way or another.
    One partial failure can and will effect all the componets electronic gremilins to come alive.
    You cant discount it. its in the chain. I dose not hurt to test them and eliminate or confirm it as a factor. Did you know that a brake light circut erro not only is caused by a bad brake light switch. A failing acccelrator pot that shows no code will cause a constant brake light circut error. why? its tied into the same circut that controls the dks fueling etc. Learned this the hard way. also failing pot will cause limp home running rich on one bank and hunting idel rough idle and all kinds of o2 codes. Talking from personal experiance. If you dont have any success. Start looking at these things good luck
    1991 Racing Dynamics K55 Sport Coupe Six Speed Original Owner 18,600 Miles
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  16. #16
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    Quote Originally Posted by E31PARTS View Post
    also failing pot will cause limp home running rich on one bank and hunting idel rough idle and all kinds of o2 codes. Talking from personal experiance. If you dont have any success. Start looking at these things good luck
    My stomp-test function quit working a while back- I wonder if this indicates a failing throttle pot. and if that would cause some of these problems...

    Whatever it is will probably be put on hold for the next couple of months, since I leave on assignment next Friday. I'll keep poking around a little more and if by some miracle I find it I'll post results. Otherwise I'll resurect the thread in November.

    Regards,
    M.R.
    2000 740i Sport Anthrazit Metalic M62TU 4.4 V8/M-Pars 214K Miles!;
    2011 Cadillac CTS-V Coupe 6A Raven Black/ 6.2L Supercharged/556HP;
    '06 Dodge Magnum SRT-8 Inferno Red/ 6.1L Hemi/ Dyno-368HP / 371lb-ft; ;
    SOLD'91 850i Calypso Red M70 5.0 V-12;
    SOLD'95 540i Schwartz MetalicM60 4.0 V8;
    SOLD'85 635CSi Cosmos BlauM30 3.5 I6;
    SOLD'97 Lexus SC400
    Maroon/4.0L DOHC V-8.;
    1970 Torino. 351C-4V/ 3.71Locker/ C6. Yeah, I'm workin' on it...;
    91 Honda CR500 (2stroke,liquid cooled MXer)/230lb/60hp/3.8lb per HP./ FMF Gnarly pipe. Top speed 105mph...in the dirt;
    1950 International/Farmall Model-M Top Speed-17mph in 5th. It's a tractor, Bish!

  17. #17
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    Quote Originally Posted by M.Rad. View Post
    My stomp-test function quit working a while back- I wonder if this indicates a failing throttle pot. and if that would cause some of these problems...

    Whatever it is will probably be put on hold for the next couple of months, since I leave on assignment next Friday. I'll keep poking around a little more and if by some miracle I find it I'll post results. Otherwise I'll resurect the thread in November.

    Regards,
    M.R.
    Funny you should say that, Because i had to do my stomp procedure a half dozen times before it kicked in. after my pot replacement all problems disappeared now it zips right through the stomp. With these cars any thing can be possible. what ever you do take you time write each thing you did down, and work through each thing one at a time, don't get too obsessed on one particular system. keep an open mind, many so called experts, including the dealers that i went to, and hook this car up to a modc could not find a code that pointed to the pot, no one could not figure out why the brake light circuit keep giving an error. They had me changing light bulbs and cleaning contacts. every time i suggested the pot to everyone, everyone said impossible. that and the fact that it is a major pia to remove and re-install
    keep me from even considering it, when i dug in to the electrical diagrams
    and noticed that the pot brake light switch and cruise ctl and clutch switch
    were tied into the same circuit as the pot, fuel and throtle ctl. i went for the pot, it made sense because when you hit the clutch or brake the signal from the switch disengages the cruise ctl and sends signal for the pot to take control of those system. I am going to assume the pot was failing and sending out a dirty or short signal, screwing up the TI injection signal, and sending or shorting the brake light switch. the point is take your time and it could be what many experts say its not. I discovered the pot has a long cable so before i took it out i removed the bolsters and pedal covers plugged in a spare and drove the car using my hand to run the spare pot. all my troubles went away, that took only about 20 minutes to do. I can lend you a spare in 3 weeks if you want to try it. In my experience. i would eliminate the easiest stuff first before you have to hit the hard wrenching stuff.
    good luck and safe travel.
    1991 Racing Dynamics K55 Sport Coupe Six Speed Original Owner 18,600 Miles
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  18. #18
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    What is the P/N for this 'pot'? Is it an assembly? How to test for its failure? What are other symptoms?

  19. #19
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    Quote Originally Posted by Dr. T View Post
    What is the P/N for this 'pot'? Is it an assembly? How to test for its failure? What are other symptoms?
    12721747630 Part number 13 price $1500 remove and install a big Piahttp://www.realoem.com/bmw/showparts...35&fg=15&hl=25
    I went to the dealer they put car car on the modec and they said nothing wrong. It did not get any and specific codes. symptoms many
    rough when hot idle. that will have you changing temps sensors.
    dk motors,misfires surging idle, limp home mode brake light circuit error.
    So you will be changing every sensor plugs plug-wires mafs computers, etc etc. A short in this dam thing will make you chase the wind.
    don't know the values don't know how to test it. The good thing is it has a long plug, so you cant get under the dash plug in a spare sit in your seat and drive the car using your hand.if your problem disappears you good to go.
    you just need a dramel small hands and plenty of pain medication for you back and a fan to circulate the air under the dash while you spend 2 hours under their putting it in and out. I am getting two spares in about 3 weeks
    if you need to borrow on your more then welcome. Also the car will run and start with the pot unplugged when i did that the car idled great, misfiring stopped surging disappeared
    Last edited by E31PARTS; 09-15-2012 at 08:44 PM.
    1991 Racing Dynamics K55 Sport Coupe Six Speed Original Owner 18,600 Miles
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  20. #20
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    Was this ever resolved?
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  21. #21
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    My 850i had the same limp home problem, just remember that earlier the Brake Light Circuit Fail Fault appeared on MID. After a few day , the Fault is erased by itself. But the no power problem persisted, no help after servicing the Servo DK, check and serviced injectors...etc.

    From your sharing of the possible fault, I am sure that my Accelerator Pedal Sensor had failed... Rich on Left Bank and exhaust black smoke..

    Just ordered a used part , hope the problem is resolved.

  22. #22
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    Quote Originally Posted by Desmon View Post
    My 850i had the same limp home problem, just remember that earlier the Brake Light Circuit Fail Fault appeared on MID. After a few day , the Fault is erased by itself. But the no power problem persisted, no help after servicing the Servo DK, check and serviced injectors...etc.

    From your sharing of the possible fault, I am sure that my Accelerator Pedal Sensor had failed... Rich on Left Bank and exhaust black smoke..

    Just ordered a used part , hope the problem is resolved.
    It will not....
    Did you swap mafs and coils to see if the problem followed?
    What did you do to those dk motors?

  23. #23
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    I had service both DK motors and even swap them, same limp mode came back ...

    My replacement accelerator pedal sensor / potentiometer just arrived... Let's see if its the main problem as Error Code had indicated Fault Code also on this part.

  24. #24
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    Singapore
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    55
    My Cars
    1991 BMW E31
    After changing Accelerator Pedal Sensor / Potentiometer which is very different to remove the securing screw at the rear using M10 socket and a small extension.

    The situation did not improve either.

    Something come to my mind, as in the forum someone mentioned before of swapping the ECU - Left Bank to Right Bank.

    Bingo , my limping mode problem is gone...

    Wonder if could be my error of fixing the wrong cabling during my removal of the ECU to replace the Chip to performance chips.

    After going through all checks...and almost gave up the Car..

    Anyway, happy now to move around with my bimmer without fear of it suddenly go into limp mode again and stuck in heavy traffic .

  25. #25
    Join Date
    Feb 2010
    Location
    Hampshire UK
    Posts
    8,864
    My Cars
    99 840ci Sport Indv
    That's great news - well done for keeping at it!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

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