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Discussion Starter #1
Aloha,
Well, I've literally searched this forum for help and cannot find the answer to this one.. Here's my situation:

2003 Mustang GT 4.6L

When start cold, it cranks but I need to press down on the gas petal to get it to start. Then as it warms up, it sputters when i press the gas petal. It has a hard time idling and sometimes shuts off. Then when I put it in drive, it stalls. As it get's warming, symptoms are worst.

Here's what I've done:

Replaced:
8 New Ignition Coils
8 New Spark Plugs
8 New Fuel Injectors
New Fuel Pump
Replaced Idle Control Valve

I scanned the OBD with a FORD scanner and no engine codes..

What should I do next? confused013.gif
 

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Did you clean out the throttle body when you replaced the IAC? I'd also take a look at the TPS to see if it's functioning correctly...could be its not reading right at all. If it's not that then I'd look towards a voltage problem. I found out when I had mine in pieces and through folks on here with a bad alternator or a lose ground it'll cause some very weird symptoms in these cars!

Is the battery light on when you're driving?


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Discussion Starter #3
Yes, I cleaned out the throttle body when I replaced the IAC.. I didn't check the TPS, but I will just replace it to eliminate that from being the problem. I will also check voltage and any loose ground cables.
Much Mahalos for the quick response. I will post updates and let you know what fixed it..

Thanks Again! :grin:
 

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Suggest having the battery and alternator tested and confirmed working good before digging deeper.

Did you use the correct IAC for the application? I believe for the 2003 model year it's the IAC without the black vent.

Is there an after market throttle body installed? If so, did you follow the manuf recommendations regarding setting the idle stop screw?

Double check that the Fuel rail pressure sensor (FRPS) intake vacuum reference line is connected and leak free. Inspect the line for raw gas. If any is found, replace the FRPS.

Here's some information on how to trouble shoot IAC/Idle issues:
Ford Mustang Forum - View Single Post - Is your mustang stumbling, dieing at idle or idling rough?
 
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