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Thread: Rough idle

  1. #1
    Join Date
    Jan 2016
    Location
    Troy, MO
    Posts
    73
    My Cars
    BMW 328i

    Rough idle

    My 1997 bmw e36 328ic m52b28 has had a rough idle for over a year now. I have replaced every single vaccine line under the intake I’ve replaced the pcv/ccv. I’ve cleaned the iac valve replaced both grommets on ccv and iac. I’ve replaced the intake gasket, throttle body gasket, valve cover gasket and the fuel injector o rings. I did replace the engine due to mine blowing up however I cannot seem to get rid of this idle it didn’t have it before I replaced the motor I have no idea what I could be. Can anyone help.

  2. #2
    Join Date
    Jun 2010
    Location
    NY
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    9,079
    My Cars
    1997 328i
    You sound like you did a good job vaccinating your engine lol.

    You could smoke test the system in case there is a leak you missed. Other things to do are servicing the injectors to make sure they are squirting equally, the service is usually pretty cheap. Replacing original ignition coils is the other important thing, there are a few aftermarket manufacturers but the longevity of them is unknown, the price however is excellent.

    https://www.ebay.com/itm/Set-of-6-Ig...7/262488221634

    - - - Updated - - -

    You could also run a bottle or Royal Purple fuel system cleaner and drive the car a little harder. Also it wouldn't hurt to do a compression check.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  3. #3
    Join Date
    Jun 2013
    Location
    Houston, TX
    Posts
    44
    My Cars
    1997 328i
    +1 for ignition coils. I had the same issues for my 328 last year, and replaced the same things (minus the whole engine). I also got re-conditioned injectors, and it all helped a little, but the thing that fixed it for good was the ignition coils.

  4. #4
    Join Date
    Jan 2016
    Location
    Troy, MO
    Posts
    73
    My Cars
    BMW 328i
    Thank you both for the suggestions. I’ve been iffy on the whole smoke test thing due to not wanting to throw money at nothing. I honestly would have never thought of the whole injector thing I’ve considered the ignition coils/ coil packs just been hesitant because again money for no fix isn’t the best case scenario.

  5. #5
    Join Date
    Jun 2010
    Location
    NY
    Posts
    9,079
    My Cars
    1997 328i
    I've seen websites listing injector cleaning before but must have mis-read the cost, ~$25/injector is not at all worth it. If you really wanted to clean them you can buy an ultrasonic cleaner and watch youtube for some ideas on making your own cleaning rig. Also you can get a rebuild kit for ~$25 with new pintles/filters/o-rings/spacers. Just make sure you get the correct pintle caps, they have a larger orifice for the pink M52 injectors.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  6. #6
    Join Date
    Jul 2004
    Location
    Houston, TX
    Posts
    12,462
    My Cars
    36 Cylinders
    It's more likely to be a vacuum leak than anything else. There are good and small Chinese smoke machines on ebay for $120 and have loads of value.
    Fuel injectors possibly.
    Coils would manifest more at higher rpm with misfires especially.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg
    - 1999 S52 Estoril M Coupe
    - 2014 328d Wagon, self-tuned, 270hp/430ft-lbs
    - 2019 M2 Competition, self-tuned, 504whp
    - 2016 Mini Cooper S

  7. #7
    Join Date
    Apr 2015
    Location
    Tennessee
    Posts
    1,736
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    1998 BMW 328i
    If you suspect injectors, google Mepeh. He will rebuild them to like new condition for about $5 per injector. A smoke machine would also be a useful tool for diagnosis.

    Sent from my VS987 using Tapatalk

  8. #8
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Cool services that Mepeh offers.. I just googled him. And his prices are great too. Alas, he doesn't ship internationally, otherwise I would have bought a set 6 injectors for my 323i (same as 325i and US M3 3.0 injectors).. Only $68.60 dollar.. Very cheap. Rebuilt and flow-matched. And no down-time because you don't have to send your old injectors in. Also, what's nice is that he hand-picks the injectors so they are all flow-matched. If you look at the youtube videos below you sometimes see that even after servicing, the original set of injectors is not perfectly flow-matched (I think I see 10% differences here and there), which will cause significant AFR changes between the cylinders, which the DME can't compensate for with its two oxygen sensors (it would need six to compensate for that).

    Links: 323i/325i/US M3 S50 injectors and the 328i injectors (cost a little more, $98, but still real cheap)..
    And here are some great videos on youtube on how he cleans the injectors.. Some of the test results are shocking: https://www.youtube.com/channel/UCH-...view=0&sort=dd . You can only imagine the damage it might do to your engine/cylinders if (one of) your injectors are (is) bad.
    Last edited by ed323i; 08-22-2018 at 11:18 AM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

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