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Thread: O2 Sensors/Rough Idle?

  1. #1
    seanef26 Guest

    Post O2 Sensors/Rough Idle?

    Can bad or old oxygen sensors contribute to a rough idle? I've had a lot of work done on my 5.0 recently and the one thing I can't seem to correct is this rough idle and slight hesitation on hard acceleration. Have changed plugs, wires, timing chain, MAP sensor, EGR valve sensor, etc... I have no idea when the o2 sensors were changed last. Is this my problem?

  2. #2
    Sly1990 Guest

    Default Re: O2 Sensors/Rough Idle?

    Did you check your TPS and IAC?
    Does you car smell fuel or carbon at the exhaust?
    Is the timing right?

    Bad IAC can cause rough idle and Hesitation when flooring the pedal....
    BAD TPS can also affect the IAC and can give you the same symptom + sometimes high idle....
    Last edited by Sly1990; 01-26-2005 at 12:40 PM.

  3. #3
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    Default Re: O2 Sensors/Rough Idle?

    Does it idle rough/hesitate while cold/warm, or only when it has warmed up? An O2 sensor can cause both of these problems but the effects will only occur once the vehicle is warmed up.
    Is it throwing any codes?

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    Default Re: O2 Sensors/Rough Idle?

    I have personally never had a bad O2 sensor without a check engine light (trouble code). When mine were bad it would cause idle problems, but as stated above there are several items that can cause it to idle poorly. You should be able to narrow it down by reading the codes.

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    Default Re: O2 Sensors/Rough Idle?

    Might need to spray your throttle valve & IAC passage with throttle cleaner.

  6. #6
    seanef26 Guest

    Default Re: O2 Sensors/Rough Idle?

    Haven't pulled codes on it yet, but the problem does seem to be worse once the car is warmed up. If I drive it right after I start it, it seems to take off pretty well. But once it's warmed up it feels like i'm towing something heavy behind me or something is holding it back.

  7. #7
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    Default Re: O2 Sensors/Rough Idle?

    The o2 sensors basically only operate when hot at idle, cruse and light to moderate acceleration. If its idling badly, or is lazy at WOT the the sensors ain't likely your problem...... I have seen a 4 cyl Stang with a bad o2 that had a stalling problem after it idled approx a minute. The sensor was so far out of calibration it was reporting rich mixture, causing the EEC to pull so much fuel when it switched to closed loop it stalled.
    Last edited by TurboCoupe50; 01-27-2005 at 06:01 PM.

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  8. #8
    jefflewis1106 Guest

    Default Re: O2 Sensors/Rough Idle?

    my t-bird had a real ruff idel come to find out it had blown a motor mount on my car they where the hydralic kind i replaced both for about 80 bucks fixed problem

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    Default Re: O2 Sensors/Rough Idle?

    eh i had rough idle and a ticking sound, i replaced my PCV valve and now its gone

    Demon- 87 LX 302, E7's, ARP bolts, Mallory Unilite Distributor, MSD 6A, Edelbrock Performer Intake, Edelbrock 600 Carb, Flowtech Lts, 5Speed, 8.8w/3.55's, Granatelli Tube K-Member & LCA's, Coil Overs, KYB 4ways, CHE arms, 3" rear drop springs, BBK C/C Plates, Fuel Cell, Bat. Relocation, Mac Mufflers, Stinger Tails, Sunpro gauges, Custom Lip Spoiler
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    Default Re: O2 Sensors/Rough Idle?

    Do all of these cars have one wire O2 sensors?

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