Rough Idle

Discussion in 'SN95 V6 Mustang Tech' started by greenmustang27, May 13, 2009.


  1. greenmustang27

    greenmustang27 New Member

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    Hi guys,

    I have a 2000 Mustang Automatic V6.

    Someone rear ended me a couple of weeks back and broke my exhaust manifold. Anyway, I got it fixed and the car ran fine.

    A week or so after I fixed it, I changed the EGR solenoid because I was checking my motor and it looked like it wasn't working. The car ran way smoother after I changed it.

    A couple of weeks after that, I changed the PCV valve and when I did that, my car started idling rough at stop lights. I bought the valve at Discount Auto Parts so I figured maybe it wasn't the right fit. So I went to Ford and bought the Motorcraft valve and replaced it. I checked the PCV hose for leaks or clogs but it was fine. The car still idled rough.

    The care actually started running way rougher and then it started sputtering. So I took a look at my exhaust and sure enough, one of the oxygen sensors was ripped - probably from the accident as my manifold actually broke off and I drove 2 or 3 blocks with my oxygen sensors wires holding it.

    Anyway, I changed the oxygen sensors and the spark plugs and spark plug wires. The car didn't sputter anymore but it still idles rough. So I decided to change the EGR valve but that didn't help either. The car still idles rough.

    I have no CEL light and I'm running out of ideas. I did notice the RPMS go up and down a little when the car is idling at stop lights (not related to the A/C).

    At first I thought it was the PCV valve, but I'm starting to think it may be related to my exhaust manifold. it was a used one after all - although the car did idle fine until I replaced the PCV valve. I'm getting frustrated.

    You guys got any ideas?
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  2. MustangLX-5.0

    MustangLX-5.0 Founding Member

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    Check the pcv hose and make sure it isn't cracked anywhere.Also you'll want to check the rubber grommet that the pcv valve fits into.If it's leaking anywhere (inside or outside edges) then that could cause idle issues.Check all vacuum hoses to rule out any vacuum leaks.I would also reset the PCM since you had a doozy of parts damaged get a scan tool or disconnect battery for 2 minutes,reconnect then start engine and wait for a couple minutes to let it re-learn idle position).The O2's and EGR should be working fine unless you still have an exhaust leak.Exhaust manifolds on 99 - 2004 V6's are known to have issues with welds cracking or metal splitting.Check to make sure the one you got from the salvage yard isn't cracked either.Make sure the pipe section between the muffler and headers isn't bent (especially near the cats).Lastly,check the idle air control sensor.It's located on the throttle body.Makke sure IAC isn'tt leaking and functioning properly.
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  3. globaltefl

    globaltefl Member

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    If the pvc valve, grommet and hose all check out, is there another place where fumes might be coming from? I have fumes coming out of the back of the engine.
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