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m50nv running rough

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    m50nv running rough

    hello I'm a new member to r3v
    I swapped a 91 m50 non vanos into a 89 325is with the help of this forum and a couple of others.
    Back ground: car starts up and runs smooth but hesitates when under full throttle and accelerating slowly. along with the hesitation there was a smell of gasoline in the oil and grey ish smoke after running for a couple minutes.
    originally used wrx fuel pump to get the car running the old one was shot, i thought maybe it was to much pressure/ flow for the stock fpr so changed the pump to a replacement/ stock, late style e30 pump. that did nothing changed the oil but after running again the smell was back. so i figured sticking injectors , i had a set of m30 injectors laying around so i put them in car ran great very smooth, no hesitation much better then before. after some research i gathered that the single pencil spray pattern of the m30 injector wasn't ideal for the m50. so i bought a set of s50 injectors remanufactured and a new fuel pressure regulator. car is back to running rough i havn't driven it much because it doesn't have an inspection sticker. Also the wiring harness for the m50 was from an e34 and as you know the e34 harness doesn't make it to the glove box so i extended it, cutting and soldering the harness. also have not changed to fuel filter yet its on my list to do.

    problem: so the problem of the hesitation is back and the idle is much worse it will die out sometimes when i first start it. do i need to run the car more for the dme to "learn" the new injectors. Could i have changed to signal going from the dme to injectors by cutting the harness and resoldering it. The hesitation seems to be alittle better the longer i run it. should i go back to the m30 injectors or stick to the s50 injectors. is there anything else that could cause the gas smell in oil?

    thanks for reading and any help is appreciated.

    #2
    I guess ill look for an e36 harness before i go back to the m30 injectors so i can rule out the harness.

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      #3
      i put the m30 injectors back in and changed the fuel filter and drained the rest of the gas tank and put fresh gas in. Runs smooth no hesitation so far. Planning on getting inspected this week, then ill be able to test it some more.
      e30 in question:

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        #4
        so I'll give an update. I got another ecu 405 this time the other is 402 and put the m50 injectors back in and its running decent i still have a problem when the motor is cold i still have some hesitation but after it warms up it seems to go away. The hesitation starts around 2000 rpm below that there is none. Temp sensor maybe?

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          #5
          so ill give another update, swapped out the coil packs and the hesitation has gone away. doesn't have the power i thought it would but maybe i'm expecting to much out of a m50.

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            #6
            good stuff man, yeh the m50 on its own is nice. I know what missing in that m50 though...
            .................................................. ...................sigpic
            .................................................. ............................. ......M50B25 3.1L stroker

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