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1985 318 running issues

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    1985 318 running issues

    Hello everybody, I'm new to these forums and this is my first post here so please forgive me if I posted in the wrong location, but I have been having quite some difficulties with my e30. I got it from a junk yard and got it running rebuilding or replacing almost everything on the car except for the engine itself. I have been driving it around for a while, but one day my water pump started leaking, so I replaced the water pump and thermostat. At this time I also attempted to fit a strut bar, which did not fit due to distributor clearance. After replacing the water pump and thermostat, it is having an extremely difficult time starting and running. So far I have replaced: thermotime switch, plug wires and plugs about 5 times (running extremely rich and fouling plugs after only a couple days of starting and testing, only Bosch wr9ds), cap, rotor, coolant temp sensor, and fuel pump relay. I have also replaced/made a distributor ground, valve cover ground, and alternator ground, and checked ignition timing. Before the starting problem there was no throttle stop screw so I replaced that as well and properly set the tension for idle and readjusted throttle switch (has also been replaced recently). Currently the only way I have been able to get an idle with no misfire is through a series of swapping in a fuel pump relay and a jumper wire, where it will start rather hard, but starts. After running for anywhere for 30 seconds to 15 minutes it will eventually die out, being able to take throttle with a rough recovery/hesitation off of it. It also will often not rev up above 2k without bogging out. Any help would be greatly appreciated and I apologize for the lengthy read and if I posted in the wrong location.

    #2
    Super rich conditions are usually the ECU on the M10 318i. Make sure to get the correct ECU for the M10 - there were two, early and late, on North American cars. An early ECU will not run a later car. The early version had the one-wire oxygen sensor.

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      #3
      Originally posted by packratbimmer View Post
      Super rich conditions are usually the ECU on the M10 318i. Make sure to get the correct ECU for the M10 - there were two, early and late, on North American cars. An early ECU will not run a later car. The early version had the one-wire oxygen sensor.
      I have gotten a second ecu, from an early 318 with the one wire o2 sensor, running slightly better but still rich and sputtering out after some time. I forgot to mention I have also replaced the o2 sensor. I stole an airflow meter from a friend, but I doubt it will change anything as the one I have tested normally. Could it be a fault in the wiring harness? I noticed in the wiring diagrams g102 is the ground for many components that could affect a rich condition but I've been having trouble finding g102. Thank you for the reply!

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        #4
        If you have a later car with a three wire oxygen sensor, I'm surprised that an early ECU will even start the car. What are the last thee numbers on your two ECUs? I think the early ECUs ended 310 and the later ones 328, but not sure on the latter. My experience back in the day was that an early ECU would not run a late car, but a late ECU would run an early car. I only had one ECU blow on me back in the day and when it did, it blew full rich black smoke out the tail. A replacement ECU solved the problem immediately. I would test the harness one wire at a time through the connector inside the glovebox, per the Bentley manual, because yes, the wiring could very well be compromised.

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          #5
          I have a 1985 318i. I was recently experiencing a rich running condition as evidenced by gasoline smell and reduced MPG. I replaced the fuel pressure regulator and the car would not start. I next replaced the O2 sensor and the car would still not start. I then replaced the spark plugs and the car started, but after running for 15 minutes, the new plugs seemed fouled. I removed and cleaned the plugs and replaced the temperature sensor (blue plug) and all was good. The car started easily, reduced fuel smell, the car ran well, and MPG was increased. However, it experienced a rich running condition again to the extent it would not run. I then cleaned up the fouled spark plugs and unplugged the barometric pressure (altimeter) sensor (P/N 13621286679) which tested faulty. Unplugging the barometric pressure sensor has been an issue in the S14 world for sometime (https://s14net.vbulletin.net/forum/s...r-disconnected). That has seemed to mostly correct the problem, at least for now. However, the initial idle still is not perfect. I have a new barometric pressure sensor and a rebuilt AFM and ECU/DME on the way. Good luck!

          Update (05/16/2024): I installed the new barometric pressure sensor and that has resolved the rich condition and stabilized the initial idle. Joy! I don’t want to jinx anything, but all is working so well I am going to hold off on installation of the rebuilt AFM and ECU/DME until I know I need them. I understood from the S14 people that a defective barometric pressure sensor could cause a potentially dangerous lean condition, but I did not really think about it causing a rich condition. However, it makes sense. Never a dull moment owning a 39 year old car with an M10 engine.
          Last edited by robertloll1; 05-16-2024, 08:35 AM.

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