Rough/Surging Idle (Intermittent)



1999 Ford Taurus, 3.0L, DOHC, 24V.

Mileage - 68,000.

Summary - I have experienced a rough idle with this vehicle that is unpredictable and irregular. The RPM will dip very low but the PCM will catch and raise the engine speed just before the vehicle stalls. I have recently cleaned the air filter (K&N) and the throttle body. I have reasons to believe it may be fuel related but definitely not certain. Some insight would be greatly appreciated.


Always start at the basics and work your way north when engine performance goes south: new/recent spark plugs and wires, fuel filter, air filter, pcv valve. Try this: with the ignition switch switch OFF, disconnect the idle air control valve wires on the throttle body. Start the engine. If the engine runs smoother, the fault could be the idle air control valve. Is there a check engine light?


Thank you for your response. No check engine light and the Ford dealer did tell me IAC valves are notorious for failing in the summer months due to carbon buildup. The problem here lies in that this condition is very irregular and happens maybe once every few weeks-month. Changing the pcv is on my do- to-list; Will the vehicle be able to maintain its idle state if the IAC is unplugged? MJS


My mother-in-law’s Taurus had the same problem. Turned out to be the throttle position sensor. They are about $40.00 at the parts store and take about 15min. to change.