BMW 328 m50 manifold. fitting 325 throttle body.

Thread in 'Technical Questions' started by littleT_23, Jan 13, 2013.

  1. littleT_23

    littleT_23 Member

    Joined:
    Jan 14, 2010
    Posts:
    879
    Likes Received:
    0
    Hi I have fitted the 325 M50 manifold to my 328. Runs fine at the top end of the rev range but in between 900 and 2000 revs it feels choked and runs lumpy. I ve checked for vacum leaks, checked coil packs, plugs, cleaned throttle body and fitted the 328 iat odi whats it sensor in the elbow and made sure it had no air leaks.

    I have stuck with the 328 throttle body and still have the 325 one that came with my M50 manifold. Was speaking to someone yesterday who have fitted one to there 328 and to fit the 325 throttle body all they ve done is blank off the extra hose connection on it.

    So what I m asking is. Has anyone else fitted the 325 throttle body and how to do it. And is it worth changing? :smash:
     
  2. GB / John

    GB / John NDC Runner Up 2012

    Joined:
    Feb 2, 2008
    Posts:
    2,213
    Likes Received:
    0
    No need to fit the 325 throttle body, 328 works just fine. Did you use 2 rubber seals when fitting 328 throttle body or use a rubber gasket? If not, then it might be leaking from there.
     
  3. littleT_23

    littleT_23 Member

    Joined:
    Jan 14, 2010
    Posts:
    879
    Likes Received:
    0
    I m using the m50 conversion kit from the states which comes with a double wide rubber seal.

    I main issue is it wont cruise at low speeds. just coughs and spits when its up to temperature. drives fine when cold.

    does the 328 throttle body have any adjustment on it like the 325 one.
     
  4. GB / John

    GB / John NDC Runner Up 2012

    Joined:
    Feb 2, 2008
    Posts:
    2,213
    Likes Received:
    0
    only adjustment is on the cable I think. You checked the ICV hose? Could be something else like Nikasil etc as a worse extreme.

    Have you checked cable if its catching anything? Dumb question I know, but pug 406 did the same recently sorted it by moving a cable.
     
  5. superclarkey

    superclarkey DORITECH MOTORSPORT

    Joined:
    Aug 30, 2004
    Posts:
    18,343
    Likes Received:
    3
    Can i ask how you tested for vacuum leaks ?
     
  6. littleT_23

    littleT_23 Member

    Joined:
    Jan 14, 2010
    Posts:
    879
    Likes Received:
    0
    sprayed around using a can of easy start. intially found the injectors were leaking air so ordered and fitted 14.5 mm o rings and now there fine.
     
  7. superclarkey

    superclarkey DORITECH MOTORSPORT

    Joined:
    Aug 30, 2004
    Posts:
    18,343
    Likes Received:
    3
    sounds to me like an air leak on one of the runners... you need to spoke test it really mate.
     
  8. littleT_23

    littleT_23 Member

    Joined:
    Jan 14, 2010
    Posts:
    879
    Likes Received:
    0
    what does that mean. A crack in me manifold.
     
  9. superclarkey

    superclarkey DORITECH MOTORSPORT

    Joined:
    Aug 30, 2004
    Posts:
    18,343
    Likes Received:
    3
    We have the same sort of problems on the Nissan Skylines, however the RB26 have a throttle body per cylinder, the gaskets fail and they miss low down in the rev range and upto around 2000-3000 rpm, then clear as they go up the rev band, now clearly this isn't turbo'ed but at idle that will see a massive vacume with throttle plate closed, and as you open up throttle and it gets to the point where it can flow more throttle plate and less through the leak the problem seems to kinda clear up.. so I would be tempted to pull manifold of as it only take about 20mins and check the seals, I'm guessing you've use new ones ? I always use an RTV type sealent on them too to make sure they seal properly.

    The M60 v8 engines are terrible for this kinda problem too.
     
  10. littleT_23

    littleT_23 Member

    Joined:
    Jan 14, 2010
    Posts:
    879
    Likes Received:
    0
    Yeah new seals came with the kit. I ll have another good spray around the manifold before pulling it off.

    Bought another can of easy start and carb cleaner. Had the car sitting on idle and sprayed everywhere. All over and under manifold, carbon canistor, PCB valve and breather pipes, throttle bottle seal and rubber elbow, around the injectors. Around idle valve and hose under rubber elbow and oat sensor. And the revs didn't dip or rise at all.

    I think I ll just have to give it a good run and see if it sorts it self out. If not then pull the manifold and put the standard one on. Also I did buy a new crank sensor so might just bung that in and see if that helps as the camshaft sensor was renewed back in june.

    If it runs smooth with the standard manifold then will buy another m50 and start again.
     
    #10 littleT_23, Jan 14, 2013
    Last edited: Jan 14, 2013

Share This Page