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Rough Idle on a 2008 Ford Focus

Gabriel_PittGabriel_Pitt (effective against Russian warships)Registered User regular
in Help / Advice Forum
My car (110,000 miles) has developed a rough vibration when idling, at lights or stop signs. The tachyometer also will peridically pulse between 600~1000 rpm when at idle, but everything clears up and runs fine.

If it was an earlier model, I'd blame the RPM on a problem with the idle air control solenoid, but appreantly this is no longer an easily changed, discrete unit, and is now part of the throttle module. The vibration, maybe too, although the fact that the vibration is constant at idle, and the RPM variation is not, makes me think that the former might be a problem with the engine mount.

Is this enough for anyone else to lend analysis or feedback before I take it into the garage?

Posts

  • dispatch.odispatch.o Registered User regular
    Sounds like my 2002 Santa Fe, but being an automatic and while it initially would just rev at stop signs, eventually the engine would floor and fight my brakes as though I was hitting the gas. It turned out to be idle air sensor (controller) and I want to say a vacuum issue. I'd just be prepared to drop it in neutral / pull the e brake at any second when you're at a light or stop sign until you fix it. Thing almost drove into the wall of a parking garage the first time it happened when I was pulling in to a space.

    I'm not a mechanic or anything and I probably have the part names not exactly right. Having to kill my car at a light because it really wanted to go forward though was kind of horrifying so be careful.

  • mRahmanimRahmani DetroitRegistered User regular
    Spark plugs and wires are probably due at that mileage. Air filter too if it hasn't been done in a while.

    Interestingly, my brothers Focus (2006) had a similar vibration issue at the same mileage, though I don't know if his rpm was pulsating like yours. On his it was worn engine mounts, and they eventually got so bad that the engine started making a loud banging sound against the frame when driving. Fixed the mounts and suddenly it was smooth again.

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  • DarkewolfeDarkewolfe Registered User regular
    edited November 2016
    Gabriel_Pitt wrote: »
    My car (110,000 miles) has developed a rough vibration when idling, at lights or stop signs. The tachyometer also will peridically pulse between 600~1000 rpm when at idle, but everything clears up and runs fine.

    If it was an earlier model, I'd blame the RPM on a problem with the idle air control solenoid, but appreantly this is no longer an easily changed, discrete unit, and is now part of the throttle module. The vibration, maybe too, although the fact that the vibration is constant at idle, and the RPM variation is not, makes me think that the former might be a problem with the engine mount.

    Is this enough for anyone else to lend analysis or feedback before I take it into the garage?

    Is it strongest while idling, or at the end of the deceleration when coming to a stop for the light/sign?

    Also, mRahmani has a good poinit. Is it just vibration, or is there any banging sound?

    Edit edit: Get it to vibrate while idling, then put it in neutral. Internet says if that gets the vibration to stop, it's probably a mount problem, not plugs or air flow.

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  • BursarBursar Hee Noooo! PDX areaRegistered User regular
    My car definitely developed an engine mount problem at around 140k miles. It appears as a really rough idle only when stopped and in gear (it's present when idling, but much less so). After speaking with my mechanic, the issue is that the rubber pads the engine normally would rest on have hardened, so now any general vibration in the engine is getting transferred to the parts where I can feel it. Of course, fixing it would cost ~$1000 because they'd have to pull everything out to replace those pads...

    So I'm just living with Magic Fingers at stoplights and putting up with it at this point.

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  • Gabriel_PittGabriel_Pitt (effective against Russian warships) Registered User regular
    Darkewolfe wrote: »
    Gabriel_Pitt wrote: »
    My car (110,000 miles) has developed a rough vibration when idling, at lights or stop signs. The tachyometer also will peridically pulse between 600~1000 rpm when at idle, but everything clears up and runs fine.

    If it was an earlier model, I'd blame the RPM on a problem with the idle air control solenoid, but appreantly this is no longer an easily changed, discrete unit, and is now part of the throttle module. The vibration, maybe too, although the fact that the vibration is constant at idle, and the RPM variation is not, makes me think that the former might be a problem with the engine mount.

    Is this enough for anyone else to lend analysis or feedback before I take it into the garage?

    Is it strongest while idling, or at the end of the deceleration when coming to a stop for the light/sign?

    Also, mRahmani has a good poinit. Is it just vibration, or is there any banging sound?

    Edit edit: Get it to vibrate while idling, then put it in neutral. Internet says if that gets the vibration to stop, it's probably a mount problem, not plugs or air flow.

    Vibration is strongest at idle, and it's just vibration. If there was banging too the problem would be pretty easy to pinpoint. I'll give the neutral test a shot on the way home today and see what that tells me.

    Much appreciated!

  • Gabriel_PittGabriel_Pitt (effective against Russian warships) Registered User regular
    Interestingly, when I put the car in neutral, the vibration decreases, but the pulsing of the tachometer became more regular. So maybe it's a problem with the mounts AND the throttle module! Exciting!

  • BlazeFireBlazeFire Registered User regular
    No codes being thrown I assume, since you didn't mention it?

    When were the sparkplugs and coils replaced?

  • Gabriel_PittGabriel_Pitt (effective against Russian warships) Registered User regular
    I completly forgot about the plugs. They're about 5k miles overdue for replacement.

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