QUESTON: My mustang cobra ( forged motor) will start up then shut right off

[TheSnake9798]

It will start up and continue to run if I keep my foot on the pedal... but as soon as let off the gas the rpms drop and the car shuts off.

Any one know why this is happening? Thank you.

 

[wmburns]

How to troubleshoot idle IAC problems

What Model year car are we dealing with?

My first guess is the IAC is not regulating the idle air flow or there is a vacuum leak in the intake tube between the MAF and TB. This could also be a weak cylinder(s) not pulling their weight. How does the car run otherwise?

How long has this problem been going on? I ask because after a battery disconnect, the PCM needs time to re-learn new idle trim values. Has the PCM been given enough time to learn?

Confirm +12 volts to the IAC red power wire key on. If not, there is no power to the IAC.

Do you have access to an ODB2 scanner that can monitor operational data? Would help to know what the IAC duty cycle (percent) is.

For more information on how the troubleshoot IAC problems, check out post #3

http://www.stangnet.com/mustang-forums/810729-starts-but-dies-idle-help.html

 

[spade]

+1 for IAC.
Tap on it with a screw driver. Then fire the car up and see if it will stay running.