Hey what does the PFC use to control and stabilize the idle?

 

I would also like to know since im having a few idle troubles myself.

 

Maybe someone else can confirm or deny this, but I imagine it uses the factory Idle Speed Control system. It adjusts duty cyle of the solenoid to control how much air enters at idle using a dampened feedback loop.

 

I know that Chuck posted that ISC was one of the things that could be removed. I just removed it and all of my emissions and now am having some serious issues. Hopefully someone with more experience with this will post soon.

 

The PFC does use the stock ISC to control idle under varying conditions. Chuck has removed his and has a write-up about what is required. Most of the rest of us just leave it -- mine works pretty well in almost any condition. However, I did have to replace my ISC last year.

Unless you really know what you're doing or are willing to put the time in that Chuck has to adjust everything, I would leave it alone.

 

The stock ECU uses the ISC to control air flow, and O2 sensor to control fuel lAFR level. The idle speeds are fixed.

The PFC also has idle timing control and adjustable idle speeds.

But remember that all control systems use some type of feedback system, and are programmed to work within specific boundaries of the parameters( fuel, air flow, rpm, TPS voltage, etc.). A very modded engine with low back pressure, and/or large ports often start to idle on the edge or out of range of these parameters and thus will not idle correctly, or poorly.

My car started having idle control issues right after I went DP, hi-flow cat and cat back even with the stock ECU ,and with and XS reprogrammed ECU back around 1995.

With the PFC mine use to work ( had to adjusted it differently between summer and winter using the air bleed screw) untill I removed the fuel purge valve system from my car. Then I had to open the throttle more to get the engine to idle. This must have pushed the TPS voltage out of range, and my engine revs would oscillate no matter what I did. So I removed the ISC control and went to 100% manual control of fuel and timing.