Redneck1465

imp

If changing out only the IAC resulted in the new problem, no other changes were made, ya gotta suspect the IAC somehow. Check it's coil resistance with a DC Ohmmeter, compare that to the old IAC coil. The IAC has a solenoid in it which opens and closes a valve allowing air to bypass the Throttle Plate. When starting, the IAC pulls wide-open while cranking; if it doesn't open, the engine will flood with fuel. Check that, too. Pull a spark plug, check it's not wet with gas.

wbrockstar

I would pull the iac back off the throttle body,leave it plugged in then turn the key on to see if the valve is opening.If it isnt opening,it may require you to crank the engine instead of just turning the key on.If it isnt opening, the iac or its wiring is suspect.The red wire should have 12volts key on.I believe the other wire should have less than 1volt.To test the iac,set the multimeter **** to test ohms.Touch each meter lead to a iac terminal,with the iac harness disconnected,take a reading,then reverse the meter leads on the iac terminals & take another reading.One reading should show 7-13 ohms then
when you reverse the meter leads on the terminals,the meter should show a very high,OL or infinite ohm reading.
Now touch one lead directly to the iac housing,touch the other lead to either iac terminal & take a reading then move the lead from that terminal to the other iac terminal & take another reading.The meter should show very high,OL or infinite ohms.If any of the tests above fail,the iac is bad.

dawson1112

Im interested to know what year 5.0l engine you put in the car. Are you using the early model intake set up from a 87-93 or are you using the late model 94-95 intake set up. The reason I ask is because the IAC mounts upside down on the early models compared to the late model 94-95 cars. Maybe you have the wrong year IAC and its just blocked off because its mounted wrong.

imp

Great info! imp

Redneck1465

wbrockstar

Are you using a 94-95 5.0 Mustang harness?? Is the new iac for a 94-95 5.0 or 99 5.0 Explorer and did the tps wires match up correctly between the Explorer tps and the main harness you're using ??
This is off topic,but did you leave the stock cam in the Explorer engine or did you swap to a better cam??

imp

Good points! Many items in Explorer 5.0s were different: Distributorless Ignition, different exhaust manifolds, heads, etc., possibly IAC also. imp

Redneck1465

I am using the 94/95 wiring harness with a IAC for a 94/95 and a fox body throttle body its a very common swap. I wired the TPS wires up to match up for the harness. The car runs ok with the old IAC it just hangs the idle at times. And yes Imp I know that...the explorer 5.0s are a pretty common swap due to the ability to drop a distributer in and the GT-40P heads and intake where very comparable to the old cobra intakes.

It still has the stock explorer cam just because I wanted to get it running well and consistently before I did a cam job on it. Its not an amazing cam but it delivers a ton of torque at lower RPM.

wbrockstar

I would try using propane/carb cleaner to spray around all gaskets on the iac,throttle body,egr valve,etc to see if the idle surges when doing so,to check for vacuum leaks.If youve got one of those small mirrors on a wand,look inside the throttle body to make sure the iac valve passages are perfectly aligned with the holes in the throttle body.Misalignment there can cause wheezing,whistling,surging. Check tps Vref & Signal voltage. Vref=5 volts.....Signal=.50-1.19 volts - closed throttle & voltage should increase/decrease smoothly from
closed to wot to closed throttle.WOT voltage should=signal closed throttle voltage + 2.71 volts.