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318i High Idle Speed

Discussion in 'E30 (1984-1993)' started by 84BURGUNDROT318I, Mar 7, 2008.

    84BURGUNDROT318I guest

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    hi, first post to the forum, i have an 84 318i runs great, except when it warms up it idles around 2200 rpm. i tried to reset the service indicator lights by crossing 2 of the wires in the service connector. i have sucessfully done this before with the diagram in front of me, but i tried to do it without it and must have shorted something out. now the car will start fine and warm up fine, but once it warm the rpms will increase to around 2200. also the temp gauge isnt working. im thinking it has to do with the check control circuit board, maybe the batteries are dead or i shorted them out. the fuse for the idle control valve is fine and if you unplug the idle air control valve the idle will go irratic like its supposed to. it just seems somehow, the car doesnt know that its warmed up. this really bothers me, and id actually pay to have it fixed if thats the case. and about the blue and white of attleboro guy, i took it there for a similar problem, {that time it turned out to be a fuse which i replaced myself} only after paying him 200 dollars to install a penny (no lie) with a hole drilled in it between the idle air control valve and the tubing to the throttle body. so it wont be going to him for this problem. if anyone , has any ideas id like to give them a try. this is my 2nd car and i do miss driving it, i guess its drivable but i look silly at redlights revving at 2200. but it did get alot better gas mileage than my maxima. any help would be appreciated.

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    Do you have a copy of the Bentley E30 service manual? If not I would highly recommend purchasing one so that you can follow some of the troubleshooting procedures.

    Your idle problem could be caused by several different components/issues, the idle control unit, the idle control valve, the throttle position switch, the coolant temp sender, coolant temp switch, the airflow meter and vacuum leaks.

    First I would make sure there are no vacuum leaks by inspecting all of the hoses under the hood. Most especially check the boot that attaches the airflow meter to the throttle body. These tend to crack in the corrugated area.

    Have you checked that your throttle position switch is correctly adjusted or that there is not a broken wire or corrosion at the connector? The throttle position switch is located on the bottom side of the throttle body and should have continuity (0 Ohms) between pins 2 and 18 in the idle position (throttle closed).

    I do not have the values for the temp. sensors handy but this is what I would check next. Maybe try a search on Bimmerforums or another enthusiast forum for this info.
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    I don't know much about the 318's, but I would suggest it's very potentially damaging to be poking around at the service connector without knowing _exactly_ which pins you're trying to short - you hit the wrong things and you really could screw up the electronics.

    At a minimum, mark which pins with some enamel touch up paint so there's no confusion.

    It's a much better idea to opt for the Peake reset tool - even though you _can_ reset the SI by shorting, the car's electronics for that are very sensitive to the current/voltage levels involved, and shorting the pins in no way can control that, which the Peake tool does do precisely, and with no risk of damage. If you accidentally damage the car's electronics, replacing the effected parts even at EBay prices might easily exceed the relatively nominal cost of the Peake tool, never mind the time and hassle involved of figuring out which parts need replacing.

    Fwiw, I had a bad motronic that caused an idle problem, car wouldn't idle steadily after warming up. If you think a 2200 rpm idle is annoying, imagine the fun :cool: of having the engine surge constantly up and down from 600 to 1500 rpms everytime you're stopped or coasting.

    good luck, hope you resolve the problem -

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