1991 5.0 Notchback Idle/Start Issue - MustangForums.com

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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.

1991 5.0 Notchback Idle/Start Issue

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Old 02-23-2014, 05:48 PM   #1
AnotherNotch's Avatar
Join Date: Feb 2014
Vehicle: 1991 LX 5.0
Location: Florida
Posts: 1
Default 1991 5.0 Notchback Idle/Start Issue

I have a 91 5.0 Notchback. I recently installed a Vortech supercharger. Soon afterwards I developed a bad vacuum leak from the lower intake. After I replaced all of the intake gaskets the car had trouble holding an idle. So I replaced the TPS (voltage is .98), IAC, cleaned the MAF snesor and intalled an EGR blockoff plate. After that car wouldn't start however, I got it to start and run by adjusting the throttle plate screw. After I started the car I would turn the throttle screw back down to a 750 RFM idle. The car then idles fine, I can drive it, no idle surge, I can turn it off and it turns right back on.

My problem is this. Once the car sits for a period of 5 or more hours or so, the car will not start. The turn the key the RPM's goes to 1500 or so and it just shuts right off. I can get it to run by feathering the gas pedal and I can get it to run again by playing with the idle screw then turning it back down to 750 RPMs however, once it sits it won't start again.

Please HELP!!!!
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