1993 Nissan Pathfinder engine idle too high

BRENBIGTRUCK

MEMBER
1993 NISSAN PATHFINDER
6 CYL
4WD
AUTOMATIC
232,700 MILES

I just tried to smog my pathfinder and everything passed except the tech could not check timing because of the idle, which in park is about 1200-1400 rpms. In gear is about 700rpms. I checked vaccum hoses, leaks and could not find anything missing or cracked. Without buying parts and starting to change them, is there something is can do first. I checked my intake - mass air, everything looked clear and clean. Thanks for your response.

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

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 idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable, coolant temperature sensor might not be operating properly misleading the computer that the engine is still cold and computer throwing fuel at it raising the idle speed