**help** Rough Idle & Acceleration

Discussion in 'SN95 V6 Mustang Tech' started by Andrew Smith, Oct 28, 2012.


  1. Andrew Smith

    Andrew Smith New Member

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    - 2004 V6 Mustang -

    1. When starting the car the engine usually idles roughly and is very " jumpy".

    2. When accelerating at low rpms the car is very "jerky" - "shaky" and I sometimes hear a loud "bang" - "pop" noise like something in the engine is getting hit (only hear it once and doesn't happen often).

    **I replaced the fuel filter. When replacing it I disconnected the fuel inertia switch (if that's what its called) and started the car. The feeling the engine had when it was using up the rest of the fuel in the line (jumpy and sputters) is how my car feels when accelerating.**


    - What I have replaced -

    1. Fuel Filter

    2. Spark Plugs

    3. Spark Plug Wires


    - I am on a very tight budget which is why I haven't taken it into a shop. When I'm on the highway or at higher speeds (not accelerating) the car runs normal. I have been reading online and have seen things about dirty throttle body, dirty fuel injectors, vacuum leaks?

    - If anyone could help or have any idea what could be the problem please let me know. Thank you.

    ----Additional information: My check engine light has Not come on. Sometimes when I start it up, white-gray smoke comes out of the exhaust. Also my gas millage is HORRIBLE. It gets about 18mpg on the interstate.----
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  2. wmburns

    wmburns SN Certified Technician

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    Does the motor run better once it has reached full operating temperature? Does the motor run hot (or has overheated in the past)?

    When the spark plugs were changed, what were their condition?

    When the spark plug wires were changed did you use all factory standoffs and looms? Did you follow factory routing?

    Does the motor "burn" coolant?

    Take the car to your local auto parts store and have the alternator tested for excessive AC ripple (bad alternator diode). Most auto stores will do it for free.

    Try this trick. Cycle the key on/pause/off several times without cranking. Now start the motor. Does this improve starting? If so, suspect fuel pressure leak down.

    Are you positive there aren't any vacuum or exhaust leaks? Don't cut corners here as even a tiny leak will cause issues.

    When was the last time the MAF was cleaned? If it's been a while, clean the MAF. Use only products designed for the job.
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