1993 Jeep Cherokee Idles low when cold and high when warmed

DJEEP

MEMBER
1993 JEEP CHEROKEE
6 CYL
AWD
AUTOMATIC
251,000 MILES

My Idle is at 900 when I turn it on when its cold but when it warms up it idles at 2100, I have ajusted the timming and still nothing and this all started when I replaced the valve cover gasket and changed the oil to a synthetic oil and I cant get the idle right and the idle pin is down all the way. Deq in three days but they wont touch it untill the idle is below 1300. The miles might be high but it is very well maintained

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Might want to check the idle air controller and the throttle position sensor-

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective ISC motor stuck in the extended (high idle speed) position.