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Thread: M30 Issue - CPS

  1. #1
    Join Date
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    M30 Issue - CPS

    Ok so my B11 3.5 (1991 if it makes any difference) is having a weird issue with the engine cutting out while driving around. It doesn't seem to depend on operating temp, RPMs or anything like that, it could happen at any point, in any gear and at any speed. Its like there is a complete loss of power, the RPMs drop and then it will stall. The loss of power is so sudden that it usually jerks me forward and RPMs starting dropping immediately. I can hold the pedal right to the floor and occasionally it will keep it running at about 300-400 RPM then a couple seconds later it could bounce back to normal and rev fine. Sometimes it will just stall out any way. There is no check engine light being thrown so I would assume no codes either. Anyone have this issue before or have any ideas? The car is basically undriveable like this because it has happened a couple times in the middle of an intersection or going up a hill with traffic behind me.

    If anyone has any suggestions as to what the issue could be, that would be great. As a reference point as well, I just changed the plugs and the old ones looked fine so I am thinking this is not ignition related, more likely fuelling or some kind sensor. The car has 194km on it.

    Thanks.
    1995 750iL - 113km Original, Nex SS, Alpina Sofline, Alpina Lip, Slammed.
    2004 745Li - Alpina Front Bumper, Spoiler
    1990 Skyline - flares, 16x10 SSR, cage
    1983 Starlet - 4AGE, cage, flares, 13"x8
    -25 Longchamp XR4
    1994 Grand Cherokee - 36s, camo, 4 link, etc
    2003 Land Rover Discovery

  2. #2
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    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    1995 750Li
    I read through that but it mentions that the issue occurs when at speeds from 45-60mph when mine happens at any speed, even just idle. Got any other ideas?
    1995 750iL - 113km Original, Nex SS, Alpina Sofline, Alpina Lip, Slammed.
    2004 745Li - Alpina Front Bumper, Spoiler
    1990 Skyline - flares, 16x10 SSR, cage
    1983 Starlet - 4AGE, cage, flares, 13"x8
    -25 Longchamp XR4
    1994 Grand Cherokee - 36s, camo, 4 link, etc
    2003 Land Rover Discovery

  4. #4
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    Does it cut out abruptly and come back on or is it a gradual variable sputter/stumble/recovery?

    If abrupt, suspect the crank position sensor or coil

    If it stumbles, sounds like a fuel pump

    Could also be crud in the fuel tank getting sucked up against the strainer. The crud falls to the bottom of the tank, making it easy to start after sitting for awhile, but cuts out when running for a bit. This problem has confounded more than one BMW owner.
    Last edited by TheStigg; 09-17-2012 at 01:15 AM. Reason: added crud in tank scenario
    ​"The US Olympics bobsled team has renamed their sled 'Biden' because nothing has taken America downhill faster"

    TheStigg (aka "gale")
    92 735i 5-spd, turbo pending
    89 535i 5-spd (may she rest in pieces)
    94 325ic 5-spd
    87 325is

  5. #5
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    No it is an abrupt cut out, the RPMs just drop immediately. I was thinkingncrank position sensor as well, is that a common issue on the M30?
    1995 750iL - 113km Original, Nex SS, Alpina Sofline, Alpina Lip, Slammed.
    2004 745Li - Alpina Front Bumper, Spoiler
    1990 Skyline - flares, 16x10 SSR, cage
    1983 Starlet - 4AGE, cage, flares, 13"x8
    -25 Longchamp XR4
    1994 Grand Cherokee - 36s, camo, 4 link, etc
    2003 Land Rover Discovery

  6. #6
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    Definitely could be the CPS. I just replaced one last night. It has been running great all along but has 263k miles & never replaced so decided to do it before becoming trouble. Here's the old and new one:



    You can see the old one has worn a groove completely thru the metal shell, probably would have died not long from now. The spec. calls for the gap to be 0.040" +/- 0.010". The old one wasn't touching but all the grim & grit thru the years, collecting on the timing teeth ground thru it little by little.

    The lower timing cover gasket gets blamed for oil leaks, but usually it's from the upper bolt on the bracket that holds the CPS. The bolt is a leak path, so remove it and clean it and put it back in with oil resistant RTV like Permatex "Ultra Copper":

    http://evansweb.info/2003/02/19/quic...ngine-oil-leak

    I've had to do this on both of my m30's.

    If you get a new CPS, only buy the original Hella (OEM). Turner Motorsports has them for $69, BMW part no. 12141720853.

    Resistance measurement:

    https://wiki.bentleypublishers.com/d...specifications

    Even if it passes the static resistance measurement, it won't tell the whole story. You'd need to measure it with an LCR to make accurate inductance measurements at various frequencies to get meaningful dynamic readings analogous to what it delivers in real life while the engine is running.
    Last edited by TheStigg; 09-17-2012 at 02:41 PM.
    ​"The US Olympics bobsled team has renamed their sled 'Biden' because nothing has taken America downhill faster"

    TheStigg (aka "gale")
    92 735i 5-spd, turbo pending
    89 535i 5-spd (may she rest in pieces)
    94 325ic 5-spd
    87 325is

  7. #7
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    1992 735i (E32)
    How do you set the gap?
    VIN#: WBAGB4315NDB70245

    Han Solo
    : Look, Your Worshipfulness, let's get one thing straight. I take orders from just one person: me.
    Princess Leia: It's a wonder you're still alive.
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  8. #8
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    Quote Originally Posted by IamHanSolo View Post
    How do you set the gap?


    There's a bolt on the back side of the little clip angle that the sensor mounts to that can slide up or down in a slot. I set mine with a 0.040" feeler gauge between the bump on the tip of the sensor and a tooth on the harmonic balancer cog tooth. Rotate the crank so a tooth is directly under the bump on the tip of the sensor.

    Remove the air cleaner, fan, and lower splash tray to get good access to it.
    Last edited by TheStigg; 09-17-2012 at 03:18 PM. Reason: added pic
    ​"The US Olympics bobsled team has renamed their sled 'Biden' because nothing has taken America downhill faster"

    TheStigg (aka "gale")
    92 735i 5-spd, turbo pending
    89 535i 5-spd (may she rest in pieces)
    94 325ic 5-spd
    87 325is

  9. #9
    Join Date
    Apr 2011
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    Toronto Ontario
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    1995 750Li
    I'm not 100% sure the CPS is the issue. I've had other cars that have had a CPS problem before and they have always just shut off completely (with no hesitation or chance of saving them from stalling) or refused to start whereas I don't have that issue with this car. Anything else it could be or should I start with the CPS?
    1995 750iL - 113km Original, Nex SS, Alpina Sofline, Alpina Lip, Slammed.
    2004 745Li - Alpina Front Bumper, Spoiler
    1990 Skyline - flares, 16x10 SSR, cage
    1983 Starlet - 4AGE, cage, flares, 13"x8
    -25 Longchamp XR4
    1994 Grand Cherokee - 36s, camo, 4 link, etc
    2003 Land Rover Discovery

  10. #10
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    measure the resistance between pins 1 & 2 of the CPS connector, should be 540 ohms +/- 10%. The connector for the CPS is just behind the thermostat housing. There are 2 connectors, the CPS one is the one further toward the rear. Push the wire bail forward to release the plug.

    Besides the coil, other culprits could be the main DME relay or the fuel pump relay in the E-box:



    Sometimes the DME can be the problem, usually a cold solder joint but can be difficult to fine. Might be easier to swap a good used DME. They're pretty cheap on Ebay these days. I'm not sure if Alpina used the same -179 with a custom chip or if it's a stock -179. You could possibly swap chips if necessary.
    Last edited by TheStigg; 09-17-2012 at 10:44 PM.
    ​"The US Olympics bobsled team has renamed their sled 'Biden' because nothing has taken America downhill faster"

    TheStigg (aka "gale")
    92 735i 5-spd, turbo pending
    89 535i 5-spd (may she rest in pieces)
    94 325ic 5-spd
    87 325is

  11. #11
    Join Date
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    Location
    Toronto Ontario
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    My Cars
    1995 750Li
    ^^^^^^thanks, I will check those items while I am working on the car this weekend. Hopefully one of those is the culprit, they all (aside from the DME), seem like a fairly easy fix.
    1995 750iL - 113km Original, Nex SS, Alpina Sofline, Alpina Lip, Slammed.
    2004 745Li - Alpina Front Bumper, Spoiler
    1990 Skyline - flares, 16x10 SSR, cage
    1983 Starlet - 4AGE, cage, flares, 13"x8
    -25 Longchamp XR4
    1994 Grand Cherokee - 36s, camo, 4 link, etc
    2003 Land Rover Discovery

  12. #12
    Join Date
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    11/88 E32 750iL+98 E36M3
    Does somebody have a picture of an M30 engine of the engine wire loom with the plug with the clip, where the plug of the crankshaft position sensor goes in? Location and where the plug is, here on the M70 in front beween the 2 banks
    https://www.bimmerforums.com/forum/s...ex-Sensors-M70
    Shogun tricks and tips for the E32 series are HERE!

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