i installed a crane adjustable fuel pressure regulator. if i add more pressure-

should my iac adjust to allow more air into the throttle body to keep the air fuel ratio even?

or does it get to a point where it cant compensate and runs rich?

 

When you first start an engine the IAC is set to a particular number of steps depending on coolant temp. The colder the temp the more steps it is set to (richer). As the temp warms the steps are reduced (leaner). These step values are referenced in a look up table inside the PROM. The IAC is able to learn to some extent during closed loop when the coolant temp is warm. The system also will try to compensate (with injector pulse width) for a rich or lean idle based on the O2 sensor readings during closed loop.

So basically having a much higher than stock fuel pressure, (without modifying the PROM parameters) the engine idle will always run rich when it is cold, and will improve some when it is hot.

There are other settings in the PROM that effect idle too.....

If you are not into PROM tuning, you should set your fuel pressure to about 46/47 psi and call it good. My Crane AFPR however won't adjust to below 49/50 psi.....

 

thanks thats very informative.

do you know of a good reliable place to get a prom for my car? or someone who can reprogram to adjust to my new settings?