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M20B27 no throttle response

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    M20B27 no throttle response


    I've been having some recent issues with my 1987 325E. It ran, drove, and idled fine up until recently. The car had been sitting for a few days and it was nice out so I decided to take it for a quick drive around town. I let it get up to temp and went to pull it out, it got stuck in a little bit of snow so I shut it off and cleared the path. Next thing I know it won't start. It just cranked endlessly. I let it sit overnight and tried it again in the morning. It fired up after a few cranks and I was off. As I got about 5 minutes down the road the thing just stopped gaining speed. It sat at 1.5k and wouldn't go any higher than that. The car is an automatic, so when I floored it, it was able to kick down and shoot up to 3k, but it never gained any power. It didn't rev freely or feel like the transmission wasn't engaging, it just didn't gain speed despite my desperate attempts to get the thing to go. It seemed to be able to move at lower speeds, but anything over 20 and it wouldn't go any faster. It idles fine and doesn't have any misfires. I did notice however if I rev it up a bit and let off the gas quickly, the thing almost stalls out at 200rpm before catching itself last second.

    After reading a couple of other posts with sort of similar symptoms, my best guess is either the fuel filter is clogged, the fuel pump is bad, or the FPR is bad, but I wanted to double-check and see what you guys think.
    It just seems odd that it can idle fine if it is the fuel pump or a clogged filter, wouldn't the thing have difficulty with running?

    Things I've done since I got the car:
    Timing belt
    Belt Tensioner
    Water Pump
    Coolant Change
    Heater Core Thermostat
    Spark Plugs
    Distributor Cap and Rotor


    Check fuel pressure at idle before you start throwing parts.

    No pressure gauge : pinch the fuel return line hard so no fuel out and rev the engine if you see improvement then your fuel pressure is low whether pump, filter or fpr.


      I'm with Aden, sounds like fuel starvation, check the fuel pressure. Often you can borrow a fuel pressure gauge at the local auto parts stores.

      Any signs of rodent activity as the car has been sitting?

      A clogged exhaust would have similar symptoms but go with the fuel pressure first.
      2004 525i Manual - 1985 325E Coupe Manual


        Fuel starvation can also be caused by electronic sensors. Double check your TPS sensor is adjusted correctly and working, sometimes they can be soaked in oil, which is normal, oil vapor gets into it and it solidifies, gunking it up. Also consider a failing CPS sensor. Lastly, and I think your issue is most likely related to a failed AFM.
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          Check your Engine speed and engine reference sensors in the trans bell housing. Test the resistance cold and test it when the car is warm. I bet one is bad.