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Thread: Heavily Fluctuating RPM when idle, bunny hopping when driving, sulphur smell..

  1. #1
    Join Date
    Jan 2014
    Location
    UK
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    My Cars
    1997 E36 Saloon

    Heavily Fluctuating RPM when idle, bunny hopping when driving, sulphur smell..

    Hi,

    My first post, mainly because I'm new to tinkering with cars and perhaps am now paying the price lol! So I apologise in advance for any obvious errors/omissions in my post.

    Some recent background: It's a '97 E36 (130k)

    I recently replaced the air intake hose as it was split and the garage was asking £140 to replace it and £300 to replace my wiper assembly....did it all myself for £40-50. Since changing the hose, the acceleration/bite felt sharper and had no issues. The RPM has always been very stable. I made this repair last week.

    However, this week the car has quickly developed a very unstable RPM...almost to the point where it feels it will stall, but usually doesn't, lots of vibration coming through the pedals, a very sulphurous smell from the exhaust. The car barely runs as it basically bunny hops...kicks like a mule...don't know the official name for this haha, but it's undriveable. I checked the intake hose again, it's tight and all parts are attached properly to it , that longish tube that comes off it is also in place (forget the name of it.)

    Oh also should mention I put a treatment in with the petrol at the recommended dilution last week...the problem development quite soon after

    From reading on forums etc. I thought maybe it's the O2 sensor or a noob error on my intake boot installation? Any ideas?

    Thanks a lot
    Last edited by Hugekebab; 01-21-2014 at 08:13 AM.

  2. #2
    Join Date
    Mar 2010
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    NJ
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    325iC
    Well normally I'd say it's an air leak, which it still might be, you'll have to check the Intake Boot, Intake, ICV and ICV hose that runs under the manifold from the bottom of the 90 degree boot to the ICV itself. But what's curious is your fuel treatment. Have you gotten your check engine light scanned for codes?

  3. #3
    Join Date
    Jan 2004
    Location
    Kentucky
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    18,000
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    '03 Z4, '06 Forester
    Could you tell us which motor your car has? Might help narrow down some possible causes.

  4. #4
    Join Date
    Jan 2014
    Location
    UK
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    1997 E36 Saloon
    Quote Originally Posted by slocar View Post
    Could you tell us which motor your car has? Might help narrow down some possible causes.
    Hi, thanks for the replys

    It's a UK 1997 1.8L...it's the 318i se or do you need more details than that?

    Just thinking, is it ODBII compliant...wondering if it's worth picking up one of those cheap scanners off ebay
    Last edited by Hugekebab; 01-22-2014 at 05:09 PM.

  5. #5
    Join Date
    Jun 2009
    Location
    South Carolina
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    2004 330 vert 2004 X5
    Sulphur smell points at a faulty catalytic converter. Bunny hops and poor idle would definitely be a symptom of a clogged cat. If it's clogged you'll have a pretty dramatic loss of power as it warms up. At some point you won't be able to keep it running. It will just stall out. It might be worth disconnecting the exhaust and running the engine for a few seconds. If you warn the neighbors you could even run it for a minute or two. If the symptoms magically disappear...clogged cat for sure.

    Ust my 2 cents (shillings) worth
    Last edited by flyfishvt; 01-22-2014 at 05:24 PM.

  6. #6
    Join Date
    Jan 2014
    Location
    UK
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    1997 E36 Saloon
    Did the petrol treatment I put in cause this?

    It's doing all this from a cold start...
    Last edited by Hugekebab; 01-23-2014 at 07:22 AM.

  7. #7
    Join Date
    Jun 2009
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    South Carolina
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    2004 330 vert 2004 X5
    Quote Originally Posted by Hugekebab View Post
    Did the petrol treatment I put in cause this?

    It's doing all this from a cold start...
    No

  8. #8
    Join Date
    Jan 2014
    Location
    UK
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    My Cars
    1997 E36 Saloon
    Well, the AA guy said it was most leikely the MAF and a couple of friends who do a lot of work on BMWs agreed, so I swapped out the MAF for a cheap (£15)second hand bosch one (didn't want to risk buying a new one.)

    The rpm is more stable, but it's not stable. Coluld that be because there's still extra fuel in the engine? The engine still feels very chuggy on idle, but the big rpm, drops aren't happening?

    Wait and see or was it a repair fail?

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