Over the weekend I re-replaced the spark plugs, wires, and coil pack on my 92 Ranger 4.0 with 104,000 miles. I used Motorcraft copper plugs matched to original number to underhood VECI label, Motorcraft wires, but did use a new aftermarket coil. I believe the ticking I had been talking about had stopped but maybe I'm just not noticing it anymore while driving. But the coil was bad, now it's quicker to start. However, while I was doing that I had some TPS codes prior to this but after installing that BBK 66mm throttle body so I replaced the TPS and it was bad right out of the box. Check Engine Light came on immediately. I swapped back with the original Ford one and no light. I also swapped the IAC motor because I'd been noticing the idle jumping way up when driven and then put back into park. I thought it was the BBK throttle body. So I switched the BBK out with the original throttle body, installed my original TPS, and the new Standard IAC motor and it still did it. So I was reading someone had the same problem disconnected it and it ran fine. So I tried that and it does fine idles about 700 or so jumps up 750-800 with a/c on, 100 miles of driving with no Check Engine Light. So I got a bad TPS sensor and a bad IAC motor right out of the box. I guess I will go with Ford only now. Any there was too many idle issues and on/off Check Engine Lights with the BBK throttle body so I returned and reinstalled the original. It still idles way up around 2000-3000 with that new IAC connected. Do I need a new one or is it something else?

 

Good grief, you've been chasing your tail on this one. This part swapping scenario is a little difficult to follow, but if I understand where things are now, your back to the original throttle body & TPS, but with a new IAC & its not controlling idle speed like it should.
So, what happens when you disconnect the new IAC???? Rpm should drop, it might idle rough or stall with it disconnected. If rpm doesn't drop, you might have a vacuum leak. If rpm drops with the new IAC disconnected, suspect the new IAC. I replaced my OEM IAC with a BWD from Advance Auto & used an online 40% off discount code & store pickup to avoid shipping, all to ease the sticker shock, a few years back, its doing fine so far, so that might be another option for consideration. Others had reported ok results with the BWD, so that's why I decided to try that brand IAC + it was Way less expensive than the Motorcraft.
Do you still have a lit CEL, or any pending codes stored in KAM??? If so, post up All code Numbers, as they can offer up good trouble shooting clues in case you have more than one problem confusing things. Some thoughts for consideration, let us know how it goes.

 

As I stated in another post on this, I disconnected the IAC and have for at least 150000+ miles. I went to a shop and we kept chasing the codes till it got to a point that indicated something was wrong in the wire bundle. Thats when we quit and I disconnected it for good. I had replaced the TPS and IAC with no luck. it idles without help at 750-800 rpm, I did adjust the throttle stop to help it out but that was some years ago. Truck currently has 317000+ on it.

 

It did drop way down when I disconnected the iac to about 500-600 I'm guessing is more accurate now. It still worked with the a/c on too. I think it's a little low. I bought a new one from Autozone and installed it awhile ago and it seems to work fine but I only started it up and let it idle and shifted it through the gears. I was convinced that it worked right so I parked it for the night. It idles around 800-900 in park which I believe is more reasonable. It doesn't jump to 1,000 or more like before in park. But I'll have to see tomorrow when I get the engine hot and drive awhile. I believe they used Wells parts but sometimes they had outsourced Ford parts, but this one had an all black body so maybe it is Borg Warner. They had two different options same part numbers, one made in China that was all aluminum like the original and one made in Mexico. So I opted for the one made in Mexico. Everything else is good, haven't had any check engine lights in 100+ miles. Just definitely a dramatic difference in power moving back to the OEM throttle body vs the BBK but it still has respectable power. It's only a 3.08 gear too so that hurts too.

 

OK, before you drive it again, perform this base idle relearn routine & it should have the computer correctly re-learn its cold & warm idle strategy with the new IAC in place.
Let us know how it goes. https://www.ford-trucks.com/forums/s...9&postcount=12

 

When my 93 XLT started loping at idle, up and down the rpm scale, it would run better with the IAC unplugged cause it went into default mode. What I found was a big rotted out hole in the bottom of the air intake hose, right back of where it clamps to the intake...couldn't see it cause it was underneath. Your truck has a lot of miles, so I'd check all the air supply hoses...you may have a vacuum leak causing your problem.