In my previous question I mentioned I redone my exhaust system. I made it to dual instead of the original single exahust system and removed the cat. converters to get better HP since my Bronco will be used alot off-road. Since I have done this the engine idles up to around 1300-1500 rpms by itself and then idles back down to 1100 rpms. I checked the idle air position sensor by removing the wires as you suggested (while the engine wasd running) and it idled down to around 900 rpms. I took my Bronco to a mechanic friend and put his computer on it and it gave me codes relating to the EGR, ignition circuit pickup , oxygen sensor ( reading LEAN bank), and the coolant temp. sensor. I replaced the EGR tube which was broken and replaced the coolant temp sensor. The oxygen sensor is new as well but I still get CHECK ENGINE light on.
engine idles up by itself on 1990 Ford Bronco
by Visitor in Arcadia, FL on March 25, 2010
ANSWER by mastertech6371 , April 07, 2010
s i recall there is a position sensor on top of the egr valve. did you replace that? common failure. when you pull the wires of the iac motor the idle should be no more than 500 rpm. if higher, it will hunt trying to get the idle speed to manufactures specs. Roy
ANSWER by the ford man , September 28, 2010
when u remove the cat off a efi motor it looses the needed back pressure wich will cause a loss in gas mileage and the throtle possitioning sensor will not work right the engine light will not go off untill u have the computer set to the exhaust but also the inteak manafold gasket could be bad too the only way to tell if that is bad is to listen to the lifters and if thay are makeing a tick noise the gasket is bad but if it runs good i wouldnt worry bout it