Joel5.0

If the TPS closed throttle value is between .5 - 1.19 vdc (= no TPS failure codes)...... the ECM will do its job, the optimum setting (not that they are adjustable) is .7 - 1.1 vdc..... anything between that window will work fine. The reason why you keep on trying to set the idle above 672 rpms and it fails...... is b/c the idle target programmed in the computer is 672 rpms. Regardless of what changes you make, the ECM will try and reset itself to hit that target..... IOW, the computer is doing its job. Setting the TPS to the mythical value of .9xxxx is....... a myth. If the ECM cannot reach the target idle value, it will continue to attempt doing so = idle surge.