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Thread: Update on rough idle

  1. #1
    Join Date
    Nov 2005
    Posts
    257

    Default Update on rough idle

    Well, I put on brand new OEM cap rotor and wires and still no change. The old cap and rotor were pretty badly worn and the pulse sensor wire on #6 wire was broken off on the old wire set. I'm surprised there was no change in the idle.

    Actually it might be a *little* smoother but the intermittent miss is still there. Maybe I can record audio of it idling and post it here. I'm thinking maybe dirty or leaking injectors.

    Any what exactly does the pulse wire do? You'd think if it was broke off before and now it's got a new one there would be some change...

  2. #2
    Join Date
    Aug 2004
    Posts
    162

    Default Pulse Wire

    Hi,

    The pulse sensor tells the ECU when the second bank (on which #6 is) is lined up for injection. Perhaps the system has a limp mode that batch fires all six when it can't detect the #6 sensor. If this is the case, then idle won't be significantly affected.

    Sounds like you have tried all the usual suspects - boots, bellows, ICV hose, intake hose (the one buried under the manifold), booster check valve...

    Have you checked the tee fittings on the hoses? If I recall, there is one somewhere. How about the oil filler cap? Dipstick? Crank position sensor?

    Hope you solve this.

    Regards,
    Adnan

  3. #3
    Join Date
    Feb 2004
    Posts
    4,894

    Default

    Clean your AFM. Disconnect battery to reset ECU.

  4. #4
    Join Date
    Nov 2005
    Posts
    257

    Default

    Thanks for the further tips guys.

    So far I've done or had done:

    -Valves adjusted
    -New OEM plugs gapped at .032
    -New OEM O2 sensor
    -Cleaned ICV
    -Had car checked for vacuum leaks when valves where adjusted
    -Sprayed WD40 around all obvious (visible) vacuum lines including the master cylinder elbow/valve
    -Checked oil cap and did the dipstick check while engine running (pulling it out lowers the idle then back to normal, seating it raises idle then back)
    -New cap, rotor, wires.

    I'll remove and clean the AFM and do a ECU reset.

    I read something in one of the idle FAQ's that said to do a ECU reset you should disconnect the battery, jumper the terminals together for 10 min, reconnect to battery, take out for a drive reaching 5K RPM, turn off car for 5 min, run again normally for 5 min, etc or something along those lines. Is all that needed or should I just disconnect for about 10 min the reconnect?

    Any how to's on how to test the crank position sensor? (my wallets getting a little light just replacing parts that aren't the primary problem)

    Thanks

  5. #5
    Join Date
    Jan 2004
    Location
    Benneton (United Colors of)
    Posts
    3,067

    Default

    wd40 isn't going to make your idle jump the way carburetor cleaner will. try it with that instead.
    "..Torchinski v. Peterson that it is legal to carry a concealed weapon, so long the weapon is totally slick like a huge ass machine gun that you carry under a trench coat, like in the Matrix."


  6. #6
    Join Date
    Aug 2004
    Posts
    162

    Default Crank Sensor

    Hi,

    To begin with, check that the crank sensor (CPS) is not all gunked up on the sensing face. There is a spec. for clearance between the CPS and trigger wheel, which I don't know off-hand (Bentley should have it).

    I wouldn't automatically replace it without attempting this first. Also, see if something as basic as a loose mounting screw is the culprit.

    Regards,
    Adnan

  7. #7
    Join Date
    Nov 2005
    Posts
    257

    Default

    Quote Originally Posted by ryan roopnarine
    wd40 isn't going to make your idle jump the way carburetor cleaner will. try it with that instead.
    I thought the reason for RPMs changing when spraying liquid around potential vacuum leaks was because the liquid itself temporarily seals the vacuum leak resulting in a more normal mixture or running condition. I don't understand why the liquid itself would make a difference, it's just the means of sealing the leak temporarily. I could be wrong (and probably am) but that's how I thought it worked.

  8. #8
    Join Date
    Nov 2005
    Posts
    257

    Default

    Quote Originally Posted by Adnan
    Hi,

    To begin with, check that the crank sensor (CPS) is not all gunked up on the sensing face. There is a spec. for clearance between the CPS and trigger wheel, which I don't know off-hand (Bentley should have it).

    I wouldn't automatically replace it without attempting this first. Also, see if something as basic as a loose mounting screw is the culprit.

    Regards,
    Adnan

    Ok, thanks. I'll check this too..

  9. #9
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    Jan 2004
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    Benneton (United Colors of)
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    Default

    Quote Originally Posted by wjbell
    I thought the reason for RPMs changing when spraying liquid around potential vacuum leaks was because the liquid itself temporarily seals the vacuum leak resulting in a more normal mixture or running condition. I don't understand why the liquid itself would make a difference, it's just the means of sealing the leak temporarily. I could be wrong (and probably am) but that's how I thought it worked.
    ideally, it gets sucked in and burned, causing the idle to bump up and bump down noticeably, so you pick the most detectable/notable "substance". propane doesn't even work for me, from past experience, so i doubt that you'd be able to detect anything with wd40. carb cleaner just happens to be cheaper than anything else too.
    Last edited by ryan roopnarine; 04-03-2007 at 12:09 AM.
    "..Torchinski v. Peterson that it is legal to carry a concealed weapon, so long the weapon is totally slick like a huge ass machine gun that you carry under a trench coat, like in the Matrix."


  10. #10
    Join Date
    Nov 2005
    Posts
    257

    Default

    Quote Originally Posted by ryan roopnarine
    ideally, it gets sucked in and burned, causing the idle to bump up and bump down noticeably, so you pick the most detectable/notable "substance". propane doesn't even work for me, from past experience, so i doubt that you'd be able to detect anything with wd40. carb cleaner just happens to be cheaper than anything else too.
    ok, gotcha.

    Also, can anyone point me to where the crankshaft position sensor is? I couldn't find it on the realoem parts site. I'm gonna take a wild guess and look somewhere around the crankshaft in the front, but it would be nice to see a schematic of it

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