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Thread: Stalling/Cutting Out On Acceleration

  1. #1
    Join Date
    Feb 2018
    Location
    Los Angeles, CA, USA
    Posts
    16
    My Cars
    09/88 735iLA, 1985 318i

    Exclamation Stalling/Cutting Out On Acceleration

    Hey there guys. Been chugging along, slowly replacing parts on this 1989 735iL I have. Just recently discovered some good news that they already deleted the SLS and replaced the rears with E34 mounts/springs/struts. Yay!

    However, yesterday while on a drive for the first time, the engine cut out at a stoplight as a tried to pull away. Threw a check engine light and immediately went completely dead, no stumble or anything.

    Now the car starts up fine and idles fine. It revs fine when in park or neutral. However, when the car is in gear and it is given throttle, the engine chokes out and stalls unless I quickly release the acceleration. If I accelerate extremely lightly (like, nothing at all) the car will accelerate smoothly with no hesitation or stalling. It's just if I give it any real throttle, the engine cuts out completely and falls flat (doesn't die completely though) This is a stark difference from just the day before being able to go WOT from a dead stop and have the car scream down the road beautifully.

    I'm really hoping it's not a transmission issue, and it doesn't seem to be the case seeing how I can baby the car up to speed and it shifts through all gears fine. It's just impossible (or at least, embarrassing) to drive the car in traffic with the stalling/hesitation.

    I really need this car operational but I'm having the damnedest time finding any information online about anyone having similar issues -- whether it be with an E32 or an E34 that has the M30 engine.

    My only current idea is camshaft/crankshaft position sensor. I feel it must be a sensor or similar that's gone bad to have gone from driving beautifully to sudden consistent symptoms so quickly. It also doesn't feel like a fuel/ignition issue seeing that there's no stumbling of any sort, it's like the computer just full cuts the engine when given acceleration. Any leads/info would be great, otherwise it looks like I'll have to drop her off at the shop

    I'm going to go down and pull the oil filler cap while she idles to try to rule out a vacuum issue, but checking around the intake boots and such I cant find anything.

    Thanks!


    UPDATE:
    Okay, so while it told me nothing the last couple days, today I go down to start her up and immediately the OBC tells me "OIL PRESS SENSOR". So hopefully I'm looking at a quick swap of the oil pressure sensor and I'm all good? Does anyone agree with this course of action besides the car? (lol)
    Last edited by Wasabi Avocado; 10-16-2018 at 04:43 PM.

  2. #2
    Join Date
    Oct 2007
    Location
    Boca Raton, Florida
    Posts
    1,558
    My Cars
    89'750iL,98'740iL,00'M5
    My first thought was a possible bad crankshaft position sensor but then your update intrigued me. I'm not sure if these cars would cut engine if it failed to sense oil pressure, but it is fairly common on other cars so it is a possibility. Try replacing that first since it is giving you that

    Sent from my ONEPLUS A3000 using Tapatalk

    BMW 7er Website www.7er.com
    1989 BMW 735i Schwarz (sadly, sold) // 1989 BMW 750iL Cirrusblau Metallic // 1998 BMW 740iL Oxfordgrün Metallic // 2000 M5 Carbon Schwarz ///

  3. #3
    Join Date
    Feb 2018
    Location
    Los Angeles, CA, USA
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    16
    My Cars
    09/88 735iLA, 1985 318i
    So I just replaced the oil pressure sensor and it made no change (except now I'm not getting that warning).

    Maybe stalling isn't the right word -- it's just falling flat on its face. If I rev it or go WOT the engine doesn't die, it just falls completely flat like it's idling and does nothing. If I really hold it down for a second, while it's falling flat sometimes it will buck or surge a bit, which is sometimes accompanied by some backfiring (although the sound seems to be much more under the car than at the back of the tailpipe).

    Starting to seem like a timing issue, which I believe leads me to replacing the crankshaft position sensor next? It is likely original on the car, which at 168k is probably toast... but it seems that a bad CPS also leads to hard start/no start conditions, which I'm showing no signs of. Fires up and idles like a champ.

    Really don't want to just throw parts at it, but there's so much maintenance that needs done on the vehicle I will entertain any suggestions.
    Last edited by Wasabi Avocado; 10-16-2018 at 04:46 PM.

  4. #4
    Join Date
    Mar 2018
    Location
    Asia
    Posts
    94
    My Cars
    1992 E32 M60 V8 RHD
    have u check the operational of ICV?

  5. #5
    Join Date
    Oct 2008
    Location
    Romania
    Posts
    110
    My Cars
    1994 BMW E32 730i M30
    I believe it's worth doing some checks on the TPS (throttle position switch). It's an unlikely cause, but testing it costs only a bit of time.

    On a car with manual gearbox, you can just unplug the TPS and drive the car. It will idle high, but otherwise it drives fine.
    But I don't know how an automatic will behave having the TPS disconnected. If you cannot drive the car with the TPS disconnected, then test the TPS following the procedure at page 130-16 in Bentley manual. I assumed you have a mechanical throttle (no EML)
    --
    1994 E32 730i M30 manual
    ex- 2006 E86 Z4M Coupe
    ex- 1986 E28 535i

  6. #6
    Join Date
    Feb 2018
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    Los Angeles, CA, USA
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    My Cars
    09/88 735iLA, 1985 318i
    Thanks for the suggestions guys, I will check those things next. The ICV seems operational by feeling its operation, but I will test it when I have a chance. I will also give the TPS a look as it may have never had one. Worth at least making sure it's adjusted correctly.

    But on another note, I've got another update -- after doing some digging about the stomp test (which I thought would be no help to me as I've never gotten it to spit out anything but a gibberish repeating code "18-18-56-2"), I found that some cars need five pedal presses to cycle to the next code as it will not advance on its own. Maybe this is all stomp test cars and I haven't read it, or its just earlier models. Who knows? Anyways, the next code stored was empty (just repeating 2.5 sec blinks), and the last code (before it looped back to the gibberish code) was 1261: Fuel Pump Relay Control. There we go, there's a fuel delivery problem that wouldn't show any symptoms on start or idle, but could certainly make a car lose all its oomph on acceleration!

    So here's an easier riddle for the next step: is there any way to test the Fuel Pump Relay, or should I just order a new one now, or can that code point to a problem that actually isn't the FPR?
    Last edited by Wasabi Avocado; 10-17-2018 at 02:32 PM.

  7. #7
    Join Date
    Oct 2008
    Location
    Romania
    Posts
    110
    My Cars
    1994 BMW E32 730i M30
    Indeed, it is very likely that fuel starvation may cause the symptoms you described.

    I would expect that a defective fuel pump relay would randomly cut, regardless of the engine load. If you want to check it and you don't have a spare, then it's very easy to make a short jumper wire - preferably fused for 20 Amps. Remove the fuel pump relay and use the jumper wire to connect socket terminals #30 and #87. See details in Bentley manual page 160-9. Make sure that the jumper wire makes firm contact and does not come out due to vibrations. Drive the car and see what happens. Note that, with the jumper wire in place, the fuel pump will operate at all times, therefore I advise you to perform the test as quickly as possible, and then immediately remove the jumper wire when the test is over.

    Since your problem seems to have popped up all of a sudden, you may also suspect a clogged fuel filter. If your fuel filter has not been replaced during the last 50.000 Km, then change it. If it was replaced recently, and no other checks and tests seem to indicate the culprit, then replace the fuel filter regardless of its mileage.

    Once you sort out the above, then probably you should move on to testing the fuel pressure and fuel pump. For that purpose, the Bentley manual is really valuable.

    Please come back and post your findings; we are interested to learn from your case.
    --
    1994 E32 730i M30 manual
    ex- 2006 E86 Z4M Coupe
    ex- 1986 E28 535i

  8. #8
    Join Date
    Jul 2012
    Location
    South Yarmouth MA
    Posts
    550
    My Cars
    11/87 735i & 735il P/C
    Check your fuel pressure regulator. Pull off the small vacuum hose and check for any dampness (gasoline). If you have gasoline in that line, it's shot.
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  9. #9
    Join Date
    Mar 2007
    Location
    Loveland, Colorado USA
    Posts
    369
    My Cars
    1993 740i
    I had similar issues, it turned out to be the MAF.

    Check out my thread on my troubleshooting efforts: https://www.bimmerforums.com/forum/s...nt-Stall-FIXED
    '93 740i - Mine
    '13 Range Rover Sport - Hers
    '08 Land Rover LR2 - Hers
    '96 328i - Son's
    '97 328ic - Daughter's
    '87 944 Turbo - Mistress
    '74 Alfa Romeo Spider - Italian Mistress
    Northern Colorado, USA


  10. #10
    Join Date
    Mar 2007
    Location
    Loveland, Colorado USA
    Posts
    369
    My Cars
    1993 740i
    The car will actually run (a little rich, but fine) with the MAF unplugged, it uses base fuel maps rather than the MAF signal to calculate the AFR.

    You might try unplugging the MAF and driving it for a day and see if you still experience the cut out. If not, you've likely found your culprit.
    '93 740i - Mine
    '13 Range Rover Sport - Hers
    '08 Land Rover LR2 - Hers
    '96 328i - Son's
    '97 328ic - Daughter's
    '87 944 Turbo - Mistress
    '74 Alfa Romeo Spider - Italian Mistress
    Northern Colorado, USA


  11. #11
    Join Date
    Mar 2007
    Location
    Loveland, Colorado USA
    Posts
    369
    My Cars
    1993 740i
    Just curious, any progress on this?
    '93 740i - Mine
    '13 Range Rover Sport - Hers
    '08 Land Rover LR2 - Hers
    '96 328i - Son's
    '97 328ic - Daughter's
    '87 944 Turbo - Mistress
    '74 Alfa Romeo Spider - Italian Mistress
    Northern Colorado, USA


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