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Thread: Rough running engine and need help

  1. #1
    Join Date
    May 2004
    Location
    Sydney, Australia
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    2,699

    Default Rough running engine and need help

    I’ve been having some trouble with my car. It starts fine, but about 2/3 of the time it runs rough both at idle and while driving, like there is only 75% of power available or it’s running on 5 cylinders. I’m guessing it’s fuel/spark related fault. While driving it can be fine one moment and rough the next. The gas in the tank is good (refilled it with 98 RON petrol), the fuel filter was changed around 15,000kms ago, I checked all the spark plugs and they look fine.

    I’m up to checking the resistance of the spark plugs leads and, I know this sounds easy, but how do you pull the leads off the distributor? I got the top one about 20% off (number 2 cylinder), but it doesn’t move easily and I don’t want to break the connector of the lead. I’m just wary about doing this because I haven’t mucked around with the ignition before.

  2. #2
    Join Date
    Jan 2004
    Posts
    4,150

    Default

    Kris , just give the boot a 90 degree twist to free it up from the cap and then pull the boot straight off. Some are on pretty snugly but they come off . If you really have that much trouble getting them off then remove the fan and fan shroud first, then remove the dist. cap with the wires attached, then take your resistance readings from the terminals on the backside of the cap. Remember the plug wires are solid conductor so they have very little resistance in them, its the ends of the wires that have the resistance in them. 5K in the plug end and 1k in the Dist. end for a total of 6k ohms resistance on each wire.


    Quote Originally Posted by BigKriss
    I’ve been having some trouble with my car. It starts fine, but about 2/3 of the time it runs rough both at idle and while driving, like there is only 75% of power available or it’s running on 5 cylinders. I’m guessing it’s fuel/spark related fault. While driving it can be fine one moment and rough the next. The gas in the tank is good (refilled it with 98 RON petrol), the fuel filter was changed around 15,000kms ago, I checked all the spark plugs and they look fine.

    I’m up to checking the resistance of the spark plugs leads and, I know this sounds easy, but how do you pull the leads off the distributor? I got the top one about 20% off (number 2 cylinder), but it doesn’t move easily and I don’t want to break the connector of the lead. I’m just wary about doing this because I haven’t mucked around with the ignition before.


  3. #3
    Join Date
    Mar 2006
    Location
    USA
    Posts
    1,839

    Default

    i would place my finger at main system voltage. hook a volt meter with some long leads to the batt under the seat and keep it next to you, get a baseline, and see if it goes funky at the same time it starts running rough.
    Alusil, Dinan DME | ITG Air Filter | Eibach/Bilstein HD | 26/20 Swaybars | Iridium plugs | Depo/ProLumen HID | Optima batt. | no AC | Stoptech brake lines, Frozen rotors, brass bushings, Superblue

  4. #4
    Join Date
    May 2004
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    Sydney, Australia
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    Thanks Bill for your comments. BillonPa, are you saying the battery could be ****ed? Because I replaced that yesterday.

  5. #5
    Join Date
    Feb 2005
    Location
    Brisbane Australia
    Posts
    70

    Default

    As you know I have had some problems with my car's Transmission and was running rough like yours it has turned out to be a spark plug leads distributor cap and rotor now it is running well. Give that a try
    OLD BOB Brisbane Australia
    10/89 525i auto ex Japan

  6. #6
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    Mar 2006
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    USA
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    make sure the new battery is at full charge.

    i would suspect not enough current is getting to something in the motronic ignition system. or there could be corrosion on a ground or in the distributor.

    when was the last time the pulse generator was replaced?
    Alusil, Dinan DME | ITG Air Filter | Eibach/Bilstein HD | 26/20 Swaybars | Iridium plugs | Depo/ProLumen HID | Optima batt. | no AC | Stoptech brake lines, Frozen rotors, brass bushings, Superblue

  7. #7
    Join Date
    May 2004
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    No idea when the pulse generator was replaced and no idea what one is.

    Quote Originally Posted by BillionPa
    make sure the new battery is at full charge.

    i would suspect not enough current is getting to something in the motronic ignition system. or there could be corrosion on a ground or in the distributor.

    when was the last time the pulse generator was replaced?

  8. #8
    Join Date
    May 2004
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    Default

    I didn't touch anything and the car is running fine now, it was running poorly for about 10-14 days, now it's fine again ??? The idle on initially starting the car though is really poor still. I'm getting a new 02 sensor, rotor and cap soon though.

  9. #9
    Join Date
    Dec 2006
    Location
    Adelaide Hills
    Posts
    75

    Default

    Let me know where you're getting your dizzy cap from - I was quoted $225 by Adelaide Motors BMW just for the cap, with another $1260 (!!!!) for leads (because they have to be custom made????). Anybody have a source for HT leads at a reasonable price?
    Last edited by Podmore; 12-27-2006 at 11:33 PM. Reason: Wrong terminology - quoted rotor instead of cap

  10. #10
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,249

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    Buy all that from www.autohausaz.com and it will be cheaper even if you have to pay for shipping USA to AUS.
    Bulk ignition wires or tailor made sets you can buy at Kingsborne
    http://www.kingsborne.com/wire.htm

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