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Serious hesitation and stumpling problem

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  • #16
    I suggest you bring to a specialist familiar with M3 to help you solve instead of buying a lot of parts that might not be needed.

    Dont worry as soon as you find the problem and solve it, the car will be great and worth it.
    John A.
    "If your ship doesnt come in, swim to it..."

    M3 e30 2.5L | R8 v8 6mt | 996 GT3 mk1 | Integrale Evo Martini 6 | Dallara F303/4 Toms | Defender 90 NAS


    • #17
      Did you check the big rubber elbow between your air filter and the injection? Mine was cracked on the underside and exhibited the same symptoms.


      • #18
        It may be time to have your injectors serviced... they get clogged, drip and leak if you don't change your fuel filter regularly or get bad petrol.


        • #19
          Did you figure it out. I am having similar problems and no one can figure it out.



          • #20

            I wish I could give the good news that my hesitation problem is resolved. Unfortunately, it is not. I thought I had the problem resolved but it came right back. I plan on tackling the problem when the weather changes. It is now winter in NY.



            • #21

              Due to troubleshooting my car for this hesitation phantom, I have gained alot of knowledge. This is all attributed to the members of who were all willing to offer their help. I am going to try and summarize all the things I did in my attempt to solve the problem.

              1) First I would make sure that your AFM is working properly. Also check to make sure the rubber elbow that connects the AFM to the intake is not leaking. They tend to tear at the bottom. I was shocked to find a hole of approximately 3" in mine. Do a search for trouble shooting the AFM.
              2) Check your fuel delivery system. I would start by checking your fuel pressure. If it is not within spec, you will have to either replace the intank pump or external pump (or course you would make sure your filter is not clogged). Also check the fuel regulator and the hose attaching it to the fuel rail. The hose on mine had a small hole that was letting in air. Then you should check your fuel injectors. I believe this is my problem. I now know the injectors I purchased were not the correct ones. I will sort that out and post the results once the weather accommodates the swap.
              3) Check your blue coolant sensor on the coolant rail above the exhaust. This sensor regulates fuel delivery to the DME.
              4) Check the relays behind the coolant expansion tank to ensure they are operating properly.
              5) Check all your grounds (DME grounds in the glove box; ground on the exhaust side near the coolant expansion tank; ground from the oil pan to frame; alternator ground)
              6) Check to make sure you have good contact with your positive terminal behind the relays.
              7) Check to make sure you don't have a clogged catalytic converter. (You can do so by disconnecting it depending on who your neighbors are).
              8) Check your bell housing sensors originating at the harness on the drivers side near the master cylinder.
              9) Check to make sure you don't have any air leaks around your intake manifold.
              10) Check your oxygen sensor.
              11) Check your ignition system (cap, rotor, wires, plugs and coil)

              I think that about covers everything. Hope this helps you solve your problem. Please make sure you post your update when you get your car sorted out. It will help fellow members going forward.