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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.

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Old 05-16-2013, 10:11 AM   #1
90notchback90
 
Join Date: May 2013
Vehicle: 1990 ford mustang
Location: Maine
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Default Cold blooded rough idle

Why do I have such a cold blooded rough idle on my 1990 5.0 after a e303 swap? It's got hedders and flow master exhaust, thanks
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Old 05-16-2013, 10:54 AM   #2
mattdel
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2 reasons: user error when reinstalling rockers, or you never did a base idle relearn.
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Old 05-16-2013, 07:03 PM   #3
89StangGTConvertible
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Try resetting your idle, as Mattdel suggests. It's easy to do (my idle is set at 1,000 rpms, but that's just my preference with electric fan, etc.):

1. Disconnect your negative on your battery to clear/reset your computers memory. caution when ever you disconnect your battery remove the negative first then positive, reconnect in the reverse order, if you don't you can possibly cause a battery explosion or destroy your computer. Leave your battery disconnected for at least 30 mins to let the capacitors in the ECM to discharge fully.

2. Disconnect the IAC connector.

3. Reconnect your battery.

4. Start the motor, with the IAC plug disconnected.

5. Set your idle, via the stop plate screw on the throttle body, between 650-850 rpms, it is best to set it at the lowest setting to prevent idle problems, such as surging, rolling etc.

6. Turn the motor off and reconnect the plug on the IAC.

7. Start the motor at let it run for 2-4 mins at idle with all accessories off, if the motor stalls out or the idle drops to low repeat steps 4-6.

8. Once your idle is good, turn the motor off and wait 2 mins, then start it back up and run for another 2 mins with all accessories on.

9. Allow 10-20 mins to let the computer "relearn" under normal driving conditions.
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Old 05-16-2013, 07:03 PM
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