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Thread: E46 M3 S54 - Starts, Rough/Bouncy Idle, Eventually Stalls - No Error Codes

  1. #1
    Join Date
    Apr 2008
    Location
    Des Moines, IA
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    79
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    2004 BMW E46 M3 Coupe

    Question E46 M3 S54 - Starts, Rough/Bouncy Idle, Eventually Stalls - No Error Codes

    Strange issue on my 04 M3 after full engine rebuild with many new parts, engine cranks, starts, rough idles bouncing sounding like it's an old carb'd V8, might smoothen out just a tad, then after about 30 seconds or so eventually dies/stalls. No relevant codes thrown except for occasional misfires and VANOS exhaust, not consistent; I think these are caused from the rough idle and stalling events. Subsequent starts stall out almost immediately after startup. On the first startup that idles for 20-30 seconds before stalling, I can keep it alive a bit longer by giving slight throttle/blips, eventually still stalls. I performed adapations reset via ECUWorx prior to first successful crank attempt since rebuild, but will see if clearing adaptations in INPA makes any difference. I'd suspect sensors (cams, crank, TPS, etc) potential issue if related codes would show, but none do..

    Already just replaced fuel pump with DW200 255LPH, new FPR w/ new o-rings, attached vacuum hose is in good condition, new fuel filter, new fuel injector o-rings, replaced 3+ year old fuel in tank with fresh fuel (makes no difference, old fuel looks/smells practically same as fresh fuel, fuel tank is clean).. electrical side is new Interstate battery, Valeo alternator, Bavauto ignition coils, fairly new NGK spark plugs, new OE equiv. MAF sensor.. checked for vacuum leaks; using OE intake manifold clamps, I did find whilst initial troubleshooting forgot to plugin the small plastic oil vent drain hose from bottom of intake manifold to oil pan, doesn't make difference once plugged in. Disconnecting MAF makes no difference..

    Cylinders/head should have good compression, using new Supertech cut/cooper ring head gasket with new Ferrea valves, Supertech springs/retainers, ITBs cleaned, actuator had a jam but I fixed it and greased up with really good free actuation movement now, can see actuator adjusting ITBs upon startup/idle (albeit jittery due to rough idle), ICV cleaned, new PCV oil separator, using AFE stage 2 intake (boot clamps are tight). All relevant hoses are connected, no cracks/leaks. New JE FSR 87.5mm pistons/rings, H-beam 4340 lightweight rods, block decked/honed, crank polished/balanced, ARP main & head studs, refreshed/rebuilt oil pump, new chains, tensioner, etc. VANOS already rebuilt shortly prior to rebuild.. timing should be good, using new VANOS oil accumulator and related line..

    Using new ATI super damper w/ standard pulley, new tensioners, new belts, new water pump.. Mishimoto radiator w/ electric fan shroud + NPT sensor, Mishimoto oil cooler w/ braided steel oil lines..

    Thinking its sensors or software tuning at this point (but no error codes?). Originally had DME on Conforti shark injector prior to rebuild, converted to 6SM from SMG along with engine rebuild via RTD.. after a 1st successful crank but no start, car went into limp/gear mode (due to being on shark injector tune as an SMG still). I initially tried to recode ECU to 6SM settings using ECUWorx, still no start/no crank.. then reflashed ECU back to stock that was saved in the shark injector prior to injector tune being applied (back to SMG OEM tune), then used ECUWorx + INPA + NCS Dummy to code out SMG settings, etc. to get car to actually start without being in limp/gear light mode (no crank/no start) - had to code out clutch actuation US requirement for startup, I believe due to clutch pedal being wired direct to brake light switch for power; clutch pedal sensor in INPA was registering incorrectly for safety requirement upon startup attempt. If resetting adaptations in INPA doesn't fix, thinking of trying to find an equivalent stock 6SM flash to go back to, then re-code additional options again with said tools.. any suggestions are greatly appreciated!

    I'll get a video uploaded to youtube and posted to show the exact symptoms for review shortly as well.. thanks again for any insight.
    Last edited by twiceasfastasyo; 02-06-2023 at 01:59 AM.
    2004 BMW e46 ///M3 S54 3.2L I6 NA ~360BHP RTD-6SM | Fully-rebuilt motor (forged lightweight rods & FSR pistons + rebalanced crank) & suspension, Conforti shark injector tune, aFe Stage 2 intake, Megan Racing catless SS headers (ceramic coated) + Status Gruppe sec 1 rasp elim + sec 2 un-resonated X-pipe + DNA motoring muffler (LOUD)
    2013 BMW e82 135i
    ///M-Sport N55 3.0L I6 Twin-scroll Turbo ~380BHP DCT | MHD Stage 2+ tune, aFe Stage 2 intake, free-flow/catless down-pipe + unresonated mid sec + straight piped rear w/ titanium quad burnt tips (LOUD)
    2012 VW GTI Mk6 2.0TSI EA888 2.0L I4 Turbo ~250BHP 6SM | Stratified tune, IE intake, hi-flow cat/downpipe, unresonated mid sec, stock gutted muffler (Sporty, civilized)



  2. #2
    Join Date
    May 2023
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    Philadelphia, PA
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    2004 BMW M3 Coupe
    Hey, did you get anywhere with your issue? I have the exact same problem, although I haven't gotten quite as far (pretty close tho) in the troubleshooting yet. Here's a thread I posted for mine: https://forums.m3cutters.co.uk/threa...efresh.260516/

    I did find a very small leak from the intake boot, so I've just ordered new gaskets, but I'm pretty skeptical that's gonna be the real fix. If not, my next theories are O2 sensors, camshaft sensors, TPS... have seen all of those broadly suggested online, but it's tough to know how to test/proceed. Curious where you're at at this point.

  3. #3
    Join Date
    Oct 2021
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    Canada
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    2011 E92 M3
    Quote Originally Posted by mittortz View Post
    Hey, did you get anywhere with your issue? I have the exact same problem, although I haven't gotten quite as far (pretty close tho) in the troubleshooting yet. Here's a thread I posted for mine: https://forums.m3cutters.co.uk/threa...efresh.260516/

    I did find a very small leak from the intake boot, so I've just ordered new gaskets, but I'm pretty skeptical that's gonna be the real fix. If not, my next theories are O2 sensors, camshaft sensors, TPS... have seen all of those broadly suggested online, but it's tough to know how to test/proceed. Curious where you're at at this point.
    After replace the intake boot and gasket, did you see any improvement?

    Mine does the same when cold start only. I already replaced all O2 sensor, coil, plugs, TPS, and exhaust CPS too

  4. #4
    Join Date
    May 2023
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    2004 BMW M3 Coupe
    Quote Originally Posted by powershiftgear View Post
    After replace the intake boot and gasket, did you see any improvement?

    Mine does the same when cold start only. I already replaced all O2 sensor, coil, plugs, TPS, and exhaust CPS too
    Sort of. I didn't see any improvement initially. I replaced the MAF as well, still no improvement. What ended up getting me back on the road was resetting adaptions via INPA. I no longer have a rough idle or randomly dying engine. So if you've replaced all those things and haven't reset adaptions... I would definitely try that.

    But the full story for me is that this all started for me about a month and a half ago, when my car died at a stoplight and wouldn't start back up. I got the suggestion that it might be the fuel pump, so I replaced that which fixed things for exactly one week, and then it started doing the rough idle. From there, I got it up on jack stands and:
    Cleaned ITBs, ICV, and MAF sensor
    Replaced fuel filter, fuel pressure regulator, and fuel line
    Replaced accessory drive belts + pulleys
    Replaced coolant line
    Replaced intake boot gaskets
    Replaced fuel pump relay
    Replaced MAF sensor

    Along the way, forum people recommended the OBDfusion app to log fuel trims, and my LTFTs were around -11% and STFTs were like 29%, which was really weird because basically it thought it needed to be running rich and was compensating into a lean condition. Eventually I had the idea to simply reset them with INPA, and suddenly my car didn't rough idle. I've been driving it for the past week or so without serious issue. I don't know exactly what caused it in the first place, and I don't really know if any one of those specific things I did "fixed" it or not (some of them are definitely irrelevant but just things I needed to do anyway).

    However, I've continued to log my fuel trims and now my LTFTs are around +10%, which is still a significant lean condition and isn't good. I don't know how much it's in my head, but I can sort of tell there's something slightly off when initially accelerating and maybe with power in general.

    I didn't see any more leaks in the intake system after replacing the gaskets, and I had a hard time successfully smoke testing the exhaust side, but it didn't seem like there was a major leak. I've got 177k miles so I may very well need new O2 sensors (or other sensors), if those are even likely causes of a lean condition (?), but I don't really have the money right now to just start throwing parts at it, especially because I don't know if I have the skills to replace them myself. Hard to know how to proceed, and I do wonder if even a good BMW indy shop could efficiently diagnose it.

    Let me know if you see better performance after resetting adaptions and/or if you have any stats on your fuel trims, because I'm very curious if the stuff you've replaced have maybe made a difference in your case.
    Last edited by mittortz; 06-08-2023 at 03:22 PM.

  5. #5
    Join Date
    Mar 2001
    Location
    Nashville, TN
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    291
    My Cars
    1999 528is 5-Speed
    Not sure if your car is a manual, but mine is and had the same problem.

    I replaced the MAF and it ran better, but kept stalling out especially at low speeds. Well it turns out that it was the Clutch Switch Sensor.

    “Replace clutch switch sensor with new (PN 61319122700). Inspected sensor and found the mounting clip broken. This will cause idle fluctuation and cruise control not to work.”

    Basically I would depress the clutch and the sensor was failing and the car did not think I was depressing it all the way and thus, stalling out.

    It has been solid with no issue since.

  6. #6
    Join Date
    Apr 2008
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    Des Moines, IA
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    2004 BMW E46 M3 Coupe
    It turns out for me the rough idle is being caused by not performing a throttle adaptation after having removed the ITBs for the cylinder head re-work. I had already done several adaptation resets (presumably for VANOS) within both INPA and ECUWorx, but to no avail. After replacing the TPSs (both) and ICV, rough idle would still commence after start up. Right before I was trying to get another piece of software configured to try to read fuel trims, I came across a video that got me to just try the quick throttle adaptation technique by holding down gas pedal for 10 seconds after/while in position 2 with the key, then release gas pedal after turning car off and waiting 10 seconds before starting up the car (can't remember the exact order of these steps but you can find videos of it generically for BMW on youtube). Doing this immediately resolved the startup rough idle. I still get stalling after running on idle with clutch pedal disengaged after driving for a bit, but something tells me it's related to both a shot center support bearing on the driveshaft (rattles bad and makes tons of noise, vibrations) along with the clutch slave cylinder needing bled more (pedal gets a little softer/weaker as I drive, starts out initially good upon engine cold/off to initial startup).

    I'm still faced with both DSC and LWS CAN timeout errors that cause my speedometer to not work, trifecta lights on my dash.. just plugged in a brand new steering angle sensor, but still get LWS CAN timeout error after clearing codes and re-scanning (DSC timeout still exists also). Something on my CAN bus is causing communication issues throughout the chain.. just don't know what exactly. Already cleaned my left rear wheel speed sensor as well to no avail. I have a replacement sensor I need to put in this weekend to see if it helps anything... I doubt it as there's something on the CAN bus that's causing timeout problems for both my DSC and LWS/SAS!

    Also still dealing with almost consistent RPM drops to stalling when coming to a stop, pressing in the brake pedal and clutch.. already replaced camshaft position sensors and crankshaft position sensor to no avail. Also replaced clutch pedal switch with PN ending in 700 instead of the standard one that E46 non-M's use, still doesn't help.

    Does anyone know if wiring up the clutch pedal switch direct to draw from the appropriate wires to the brake light switch (as what SMG to 6SM conversion tutorials instruct to do) cause LWS and DSC timeouts, and/or stalling issues with the clutch pedal sensor? I unplugged the brake light switch to see if I could communicate with either the DSC or LWS, but no avail. I can communicate to the EWS module without any issues. So strange!
    Last edited by twiceasfastasyo; 07-13-2023 at 11:07 PM.
    2004 BMW e46 ///M3 S54 3.2L I6 NA ~360BHP RTD-6SM | Fully-rebuilt motor (forged lightweight rods & FSR pistons + rebalanced crank) & suspension, Conforti shark injector tune, aFe Stage 2 intake, Megan Racing catless SS headers (ceramic coated) + Status Gruppe sec 1 rasp elim + sec 2 un-resonated X-pipe + DNA motoring muffler (LOUD)
    2013 BMW e82 135i
    ///M-Sport N55 3.0L I6 Twin-scroll Turbo ~380BHP DCT | MHD Stage 2+ tune, aFe Stage 2 intake, free-flow/catless down-pipe + unresonated mid sec + straight piped rear w/ titanium quad burnt tips (LOUD)
    2012 VW GTI Mk6 2.0TSI EA888 2.0L I4 Turbo ~250BHP 6SM | Stratified tune, IE intake, hi-flow cat/downpipe, unresonated mid sec, stock gutted muffler (Sporty, civilized)



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