Idling Like a Pro Mod

[Elfear]

So my little dump-mobile ('93 Mercury Topaz) is idling at 2200-2500rpm for some reason. The car has gotten a tune-up recently (plugs, wires, cap, rotor, all filters, and PCV valve). I can also faintly smell gas fumes coming through the A/C vents. Otherwise the engine runs smooth. My best guess is maybe clogged fuel injectors or maybe the MAF sensor is on the fritz. Any ideas what would cause such a high idle?

 

[exdeath]

Vacuum leak, either hoses or a ruptured vacuum diaphragm, high idle and gas smell in the ac is a dead giveaway. I'd start with the pcv system since it was messed with recently, and it's large size and proximity to the firewall would produce a strong fuel odor. The hoses get hard and brittle and could have cracked when the valve was replaced. Evap system is another common cause of your symptoms (another large vacuum hose coming from the fuel tank)

Injectors or MAF have no effect on engine speed. Gas engines are throttled by air, only a real change in the amount of air entering the combustion chamber can change engine speed. All the system can do is measure that air (with the o2 sensors in the case of a vacuum leak), shrug it's shoulders, and add the correct amount of fuel.

 

[Pacfanweb]

Vacuum leak, or the Idle Air Control Valve is stuck.

The IAC valve looks like a little rocket ship, on the throttle body.

With the car idling, get a wrench, or heavy screwdriver, and tap on it firmly. If the idle changes at all, that's your problem.

Let us know, and I'll tell you how to reset the adaptive idle strategy after you've replaced it, if that's what it turns out to be.

 

[Elfear]

Awesome. Thanks for the suggestions guys. I'll check the IAC and get back to you. I'll buy some starting fluid too and check for vacuum leaks.