TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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I addressed a question to Ed Wright at Fastchips about the fast idle for a minute or 2 and he said it was the idle air control shutting down each time you start the car and there was nothing he could do about it. Has anyone either decreased the fast idle time or eliminated it? where or what is the fast idle and where is it located? if the computer controls it than there has to be a parameter in ecm that can be addressed to shorten the time or get rid of it......this just annoys the poo out of me. anyone got any ideas?
thanks
__________________ 86 IROC 305 TPI, KYB shocks, poly bushings, alochol/water injection, MSD, K&N, map relocated, Flexalite dual fans, 1.6 rollers, March pulleys, ported plenum, overlays, cat gone and 3 inch flowmaster into 2 2.5pipes, MSD 300+ wires and platinum plugs, 170 thermostat, gutted air box and all free mods, (in storage for 15 years), Fastchip stage 2
After you verify that your IAC is functioning properly, I'd be inclined to say that Ed Wright is incorrect. You can set the idle to whatever you want to in the ECM. In the ECM, the idle speed is simply function of the coolant temperature (though fuel and spark do play an indirect role).
my idle is high when I start my car too. it drops down after a while. the whole time its high, my air/fuel ratio gauge is pegged in the rich. after the idle drops, the gauge will start to bounce back and forth like its suppose too. is this the ECM switching from one loop to another?
When you initially start your car, it is in open loop. There are three values in the ECM (in the constants table) to control the delay before transitioning to closed loop- one for hot O2, one for warm O2, and one for cold O2 (cold being the longest delay). There are also two tables of values for %change to the A/F ratio in open loop- one table is a function of coolant temp and the other, RPM. The ECM runs the appropriate value from each table through an equation to determine the proper %change for any given coolant temp/RPM condition. In addition, your engine has to reach a prescribed coolant temperature before going into closed loop.
Ed may have altered both these tables and values to the point where the idle is unnecessarily high for a few minutes. On mine (since I live in Southern California where it's typically warmer) I adjusted everything way down. That is, the %change to A/F in open loop and the amount of time in open loop since the engine warms up very quickly around here.
For instance, the cold O2 delay timer for an AUJP car (1990 TPI) is 190 seconds in open loop. I adjusted it down to 60. There's simply no need for it to delay so long where it's so warm.
