pdc427

I am experiencing idle problems on an 88 5.0 GT. Each time the engine is cold started, it races at approx. 2K rpm for about 20 sec. and then idles down to about 400 rpm. It barely runs at this speed and will die if either the heat or air is turned on. Sometimes even after warmup, the engine will race between shifts but after a delaywill slow down to that extemely low idle again. I suspected a problem with the Idle Air Bypass(IAB) and after first cleaning it, I checked the solenoid coil resistance and circuit voltage. Both were within spec. If the power to the IAB is disconnected the engine will immediately die. No codes show up. Does anyone have any experience in this area? I am getting baffled. I am going to look at possible problems with the Engine Coolant Temperature Sensor(ECT) and Fuel Pressure Regulator Control(FPRC) but I don't know if this is the right track.

fourfivefour

Check for vaccume leaks or a stuck open egr valve.

pdc427

Problem solved. Checked codes again. Got code 23(throttle position sensor-signal voltage out of Self-Test specification) . Replaced sensor. Idles great now.

wht90lx

my idle has been acting up lately as well, I was thinking about just buying a new throttle body that comes with a new tps and kill two birds with one stone.