1991 Ford Bronco engine idling high

1991 FORD BRONCO
80,000 MILES • V8 • 4WD • AUTOMATIC
Avatar
JONESNAROUND
  • MEMBER
  • 1 POST
I bought a 1991 Ford Bronco; I noticed after I bought it that it was idling high, sporadically. This problem does not happen all the time; I have fixed all the vacuum leaks that I could find. I have checked for leaks around the intake manifold. IF I goose the throttle as I am stopping at a red light the idle when stopped while in drive will drop from 1000 rpms to about 600 rpms. I replaced the IACV motor because a friend’s brother said that was what was wrong. I am now tired of guessing found someone that has an ODB1 computer to check the engine. He hooked up the computer and I think there was a code 33, then he did the KOEO test at the end of the test there were four codes 13, 44, 65, 77. He said that one or two might because I did not turn the steering wheel and press the brake in the beginning in time. I have found the codes online but have know idea what they mean and what I should try next, I am getting frustrated I love the truck but I hate this problem. Please help.
May 22, 2010 at 5:46 AM
Advertisement
Avatar
RASMATAZ
  • CERTIFIED EXPERT
  • 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.
May 23, 2010 at 1:35 AM