1995 Mercury Sable High Idle

JSHUFFMAN

MEMBER
1995 MERCURY SABLE
3.0L
V6
FWD
AUTOMATIC
70,000 MILES

My daughter's Sable had repair work done. Car was stalling. Replaced IAC valve and some vacum hoses that seemed to fix the problem. Now she is having problems with high idling. Stays at around 2,000 rpms and also fluxuates up and down. If she unplugs the IAC valve, it runs graet. Had the valve exchanged for another one under warranty. I'm thinking TPS. Would love some other ideas please and thank you. Could it be the throttle body?

2 Replies

CARADIODOC

MECHANIC
33,871 POSTS

The throttle position sensor has almost no say in fuel metering and has nothing to do with idle speed. If you're going to guess, Ford had a lot of trouble in the early '90s with coolant temperature sensors. That is unusual because there is just one component in them and in all other car brands they cause extremely little trouble. The best way to verify this is with a scanner to view live data, but we find them with an ohm meter too. The resistance between the two terminals will vary with temperature, but it must hold steady while you're measuring it. If you find the resistance bouncing all over, replace the sensor.

Ford's idle air control valve is also an odd system that causes plenty of trouble, but the fact the idle speed is going up and down proves it is working. The engine speed is changing in response to something the Engine Computer is seeing, and most likely that is coolant temperature.