4.6 Idle Problems

While the Comp cams information page states that they are compatible with the stock tune. IMO it's naive to expect to get a stock idle from stage 2 cams. However I suspect that you just want it to not die without holding your foot on the gas.

Consider that while the stage 2 cams should work with the stock tune this assumes that everything else is in tip top shape. Expect the cams to make any short comings worse. Consider checking:

• the alternator
• the battery terminals
• the grounds around around the radiator core support
• vacuum leaks
• Fuel rail pressure sensor (FRPS) intake vacuum reference line.
• clean MAF

Troubleshoot IAC idle problems 1996-2004
http://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/

What about the state of the battery and alternator? Does the battery hold a charge?

Have the alternator tested for excessive AC ripple (bad diode). No excuse to skip this step as almost all auto parts stores will do it for free.

How recently has the battery been disconnected? As a reminder that it does take time for the PCM to re-learn new idle trim values. It should be expected that the idle is poor after a battery disconnect.

Is the AC on? Is the AC low on Freon or is the AC short cycling? This could also be a possible source of the issue.