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Thread: 98 M3 engine hesitation, lowend torque missing

  1. #1
    Join Date
    Jan 2007
    Location
    Lebanon
    Posts
    492
    My Cars
    E30 M3 S50B32

    98 M3 engine hesitation, lowend torque missing

    Hey guys,
    recently my car has lost a lot of lowend torque, i experienced something similar a few months back, but the torque loss was more severe, also the idle was very rough and loud.
    It turned out to be the exhaust solenoid wiring was loose. This time around i tried looking at the vanos intake side nut (that thing with 6 bolts or so in a circle) cause somebody here was saying it turned out his nut inside was loose, it wasn't that. Also i checked the solenoids resistance, checks out.
    I did some scanning with INPA, unfortunately it didnt show me the vanos, but i could confirm the TPS was right, and temp sensors, also it gave codes for the oil level sensor, but i dont think that could cause the lowend torque to be missing?
    Any idea what could be the issue? Or maybe some software that can show the vanos with the s50b32?
    Next up i'll be testing the fuel pressure but i doubt that's it since up top it's pretty ok, the missing torque is around 2k til 5k or so, then i think it's still missing some power
    1987 BMW M3 S50B32 engine swap

  2. #2
    Join Date
    Jan 2007
    Location
    Lebanon
    Posts
    492
    My Cars
    E30 M3 S50B32
    So i finally got some vanos readings! I was able to get DIS to work from links here using carsoft interface, i put what helped in the DIS + carsoft thread if anyone's interested.
    Anyways i let it do the vanos test and it passed. Then i did some live readings, the vanos seems very responsive and barely off, i had expected it to be damaged or slow due to bad seals since this is a 98 engine and i never replaced the vanos seals. I noticed at idle the exhaust vanos was at 0'cs and intake was 60'cs then as i went on part throttle while driving it would go to 20'cs for the exhaust, then at WOT the exhaust would go up to 40 or something and the intake would go low, then further up top it would also change. I always wanted to see how this vanos stuff really works while the engine is driving.

    Anyways i also checked the MAF, at idle it is 14kg/h which is within specs of others on the forum on WOT it goes to around 400kg/h or something iirc.
    The water temp sensor is 70'c or so and didn't go above 95'c (the dme pulls alot of timing if that happens) but i did see a water temp sensor code in the fault lists, not sure that matters though or if it was intermittent cause i parked it so long while testing and it got a little hot.

    The TPS seems to be working fine, it rises up linearly but it tops out at 3.2v according to the DIS, which registers full throttle, but i recall it should go to 4.0v? dunno

    So next up on my list is to change any bad spark plugs, and maybe get the fuel injectors cleaned and see how that changes stuff. and maybe buy 1 coil and start replacing each to see if it makes a difference. Then potentially a different TPS and/or MAF.

    The symptoms right now is that if i give it part throttle it'll bog and hesitate and misfire like it's running on 5cylinders or something, if i go WOT it would get better, but i still feel like it's missing torque and power especially in the lowend midrange.
    Cheers
    1987 BMW M3 S50B32 engine swap

  3. #3
    Join Date
    Jan 2007
    Location
    Lebanon
    Posts
    492
    My Cars
    E30 M3 S50B32
    So yesterday i ran into a big pot hole, then the car started stuttering a lot of i had to give it a lot of throttle so it wouldnt die.
    Next day same thing, it would start then shut off, i looked at the wires, nothing is loose, also the battery wire is fine, no leaking from below, i wonder what get loose that it's doing this.
    I found that if i remove the MAF it would start and keep idling fine, then when i put the MAF back when it was warm after a little it idle hunted for a bit then died, then ran kinda smoothly if i gave it a little throttle. I'll be driving it today to see how its running. No fault codes showed up in DIS, and the sensors seem reading fine, MAF is reading a little higher than before at around 17-20 and playing quite a bit. No vacuum leaks i could see or the big hose below the plenum. Engine grounds, relays and wires, looks fine as well. Maybe the DME wiring got a little loose i guess, i'll give that a check later.
    1987 BMW M3 S50B32 engine swap

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