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89, Bronco 5.0 AT. While driving today the idle went up to about 1400. Was working fine until then. When I'm in drive, it idles around 1000. I didn't want to drive around with the IAC unplugged. When I unplug it, works fine. Its brand new, only 4 drive cycles on it. I just put in reman engine, transmission, rebuilt transfer case, rear axle, etc. Basically everything under the body. Should I just replace the IAC? Its been awhile since I've had an issue, 1st time back on forums in years...
My 88 f150 started doing that after i replaced my iac and im not sure why but i started throwing egr codes dont remember which ones but i just went ahead and replaced egr valve, evp and the egr solenoid you can test the valve with a vacum pump just remove vacuum hose from evp which is screwed to the top of egr valve on left side of intake and apply vacuum and see if diapham shaft moves up diaphram should also hold vacuum if not valve is bad if valve is good then test evp circuit remove connector take multimeter with ignition in run position test reference voltage evp harness connector pin should be between 4 and 6 volts id check for vacuum leaks as well good luck
