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Thread: Weirdest CEL Ever! Maybe Not?

  1. #1
    Join Date
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    Weirdest CEL Ever! Maybe Not?

    Just got my 2/91 850 back up and running. Have a red CEL (left side cluster) that only lights up when idling. As soon as you use a little throttle it goes out, then comes back at idle. Everything I've read talks about a CEL staying on until the cause is fixed. Haven't seen one about this.
    Stumped...
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  2. #2
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    84 633, 91 M5, 91 850
    Have you done the stomp test?

  3. #3
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    '92 BMW 850i 6 speed
    Deleted . . .
    Last edited by Sniff38; Today at 09:15 AM. Reason: Error in info

  4. #4
    Join Date
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    TT Cayenne / SC 850
    Quote Originally Posted by masbury View Post
    Just got my 2/91 850 back up and running. Have a red CEL (left side cluster) that only lights up when idling. As soon as you use a little throttle it goes out, then comes back at idle. Everything I've read talks about a CEL staying on until the cause is fixed. Haven't seen one about this.
    Stumped...
    Maf is failing. Do you have k&n filters installed?

  5. #5
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    Dragon850 - No, I have completely stock intakes and filters, in fact, just installed new air filters. Everything is new from the intake manifolds out up to MAF's.

    I ran codes with DIS GT1 v44 and 57 and got what is essentially o2 sensors connected backwards. One bank too rich the other too lean, which is the only codes I received. I then switched the connections and received codes telling me that both banks were too lean, which tells me they are now connected correctly except for the too lean (both banks) error. Could the MAF's failing cause this, is it the O2 sensors both failing at the same time? I am also getting an EML error with light, that one or the other is disconnected after changing the O2 sensor connections. Could it be both O2's and MAF's simultaneously? The car has 166k on it and I don't know it's history. I do have a pair of known working MAF's off my '90 E32 V12 that I can try. It's a German spec car, but the MAF'S should be the same.

    I will swap the MAF's, re-run codes and report back. If there is anything else that you can think of, please let me know.

    Thanks
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  6. #6
    Join Date
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    Quote Originally Posted by masbury View Post
    Dragon850 - No, I have completely stock intakes and filters, in fact, just installed new air filters. Everything is new from the intake manifolds out up to MAF's.

    I ran codes with DIS GT1 v44 and 57 and got what is essentially o2 sensors connected backwards. One bank too rich the other too lean, which is the only codes I received. I then switched the connections and received codes telling me that both banks were too lean, which tells me they are now connected correctly except for the too lean (both banks) error. Could the MAF's failing cause this, is it the O2 sensors both failing at the same time? I am also getting an EML error with light, that one or the other is disconnected after changing the O2 sensor connections. Could it be both O2's and MAF's simultaneously? The car has 166k on it and I don't know it's history. I do have a pair of known working MAF's off my '90 E32 V12 that I can try. It's a German spec car, but the MAF'S should be the same.

    I will swap the MAF's, re-run codes and report back. If there is anything else that you can think of, please let me know.

    Thanks
    With the EML light on you likely have failing throttles that are not operating properly, you can send them to me for a rebuild if you'd like. I would start there...
    What does DIS tell you when you pull errors from EML module? "Throttle valve" fault or something similar?
    I also suggest disconnecting the batteries for 10 min after you plugged the o2 sensors in properly so the computers can relearn the adaptations correctly from the start.

  7. #7
    Join Date
    Feb 2015
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    Dragon850;

    Interesting results today. Borrowed the MAF's from my 1990 E32 750i and prior to installing them in the 850, I cleared all the codes with DIS GT1 V44. Installed both MAF's, test drove, there was no red CEL during the drive, came back to my shop and re-ran DIS and lo and behold no codes at all... No O2 codes, EML codes nor anything. It appears that both my MAF's are bad and seems to have been triggering all the codes. Unbelievable! However, there is one small problem. The orange CEL on the right side of the cluster stays on after start, but then goes off after driving the car, say within a minute. What is that CEL and without any codes what can it mean?

    Still scratching the head...
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  8. #8
    Join Date
    Jan 2004
    Location
    Toronto, Canada
    Posts
    1,207
    My Cars
    BMW 850CSi
    The orange Check light that disappears after a min or so is not the CEL, but rather Check...as in, Chcek the MID for error/trouble messages.

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