5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Rough Idle?

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Old 05-13-2008, 06:02 PM
  #1  
90notchLF
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Default Rough Idle?

By 90 5.0 has been idleing pretty rough as of late. As soon as it cuts on it sounds like it wants to cut off sometimes it does but usually it would stay on and after about a couple of minutes it idel fine.

Also when coming to a complete stop and putting it into park it sounds like it wants to die but if I give it some gas it will sat one.

Anyone know what this might be? So far Iv'e done the following to the car.....

Trans rebuilt
Spark plugs
plug wires
oil filter
fuel filter
fuel pump
oil change
air filter
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Old 05-13-2008, 09:50 PM
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90notchLF
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Default RE: Rough Idle?

bump
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Old 05-14-2008, 02:05 AM
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PJC Racing
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Default RE: Rough Idle?

Check for vacuum leaks and timing.
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Old 05-14-2008, 09:38 PM
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88fox50
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Default RE: Rough Idle?

have you ran any cleaner thru the intake? and some are opposed to it but i just added some Seafoam to my oil for a couple hundred miles before oil change and while running sprayed it gently through the intake and it actually helped smooth the car over alot, major differance for me anyway. i had similar issues.

btw ...what does "bump" mean? i see it all the time but have no clue.. good luck
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Old 05-14-2008, 10:36 PM
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highspeed
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Default RE: Rough Idle?

Ok... for one, what air filter did you use? A cheap air filter can reduce or change the direction and amount of flow to create inaccurate readings from the MAF which in turn will give bad readings to the ECM and your car will run poorly. (I actually experienced this issue first hand.)

Two... Have you tried buying the MAF cleaner from your local dealership (Yes I said it... buy it from the dealer, the cheap stuff will damage your MAF) to see if cleaning your MAF will help?

Three... Have you checked your fuel pressure through the valve located on your fuel rails? The fuel regulator could be showing some signs of age. This is common on these year models.

Four... You could have enough carbon build up around your Throttle Body that it is causingsome problems... Get some Throttle Body Cleaner from the Dealership.

Five... Check all your vacuum lines and ensure there are no vacuum leaks present.

Six... YourO2 sensorsmight be experiencing some failure, as they build up with carbon deposits they tend to give incorrect readings and sometimes go out all together.
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Old 05-15-2008, 09:20 PM
  #6  
88fox50
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Default RE: Rough Idle?

ORIGINAL: highspeed

Ok... for one, what air filter did you use? A cheap air filter can reduce or change the direction and amount of flow to create inaccurate readings from the MAF which in turn will give bad readings to the ECM and your car will run poorly. (I actually experienced this issue first hand.)

Two... Have you tried buying the MAF cleaner from your local dealership (Yes I said it... buy it from the dealer, the cheap stuff will damage your MAF) to see if cleaning your MAF will help?

Three... Have you checked your fuel pressure through the valve located on your fuel rails? The fuel regulator could be showing some signs of age. This is common on these year models.

Four... You could have enough carbon build up around your Throttle Body that it is causingsome problems... Get some Throttle Body Cleaner from the Dealership.

Five... Check all your vacuum lines and ensure there are no vacuum leaks present.

Six... YourO2 sensorsmight be experiencing some failure, as they build up with carbon deposits they tend to give incorrect readings and sometimes go out all together.

Great info.. i will be taking you advice myself!! Thanks!!
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Old 05-15-2008, 11:31 PM
  #7  
91blackmustanggt
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Default RE: Rough Idle?

is your alternator charging at idle
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