Replacement IAC

[mark22elliott]

Ive been chasing a random Idle issue, its been getting worse.

Its not a vacuum leak, Air filter, MAF, Inlet hose, re manufactured throttle body, TPS, IAC and 2 O2 sensors all new.

Through much discussion on other sites and local shops the consensus is the IAC is at fault, when its unplugged the truck struggles for rpm when cold, when its plugged in it hits 3000 rpm. the only thing that can do that is the IAC.

The "new" IAC on the truck came from Autozone and i recall was a Duralast product.

I am informed that only HITACHI and Motorcraft work.

Would love to validate this statement.

if it is true, where do i buy a Hitachi part since Motorcraft havent made this part for years. Whats the Hitachi part number, Amazon has several none of which are "listed" for a 94 ranger.

So whats everyone doing for a replacement IAC?

 

[Uncle Gump]

What engine do you have... I'd like to move this where it belongs.

The issue with IAC's... some are stepper motors and some are PWM solenoids. They work a bit differently. Our Rangers use the latter.

 

[mark22elliott]

1994 4.0 V6, would really appreciate knowing a replacement that everyone feels will work

 

[lil_Blue_Ford]

Have you checked the TPS for proper setting and all? I had a problem once with replacing the TPS and the replacement would cause a 3k RPM “idle”. Unplugging the IAC would reduce the RPM, but the problem was a defective TPS. I don’t remember the exact procedure, but you use a multimeter to probe certain wires on the TPS to verify it’s receiving and sending the correct voltage

 

[mark22elliott]

At idle TPS is 0.84v, rises with no flat spots to 4.54v. i think its good.

 

[mark22elliott]

At cold with IAC plugged in RPM=3,000, Unplug it and it drops to almost stalling 600rpm.

After warmup with IAC plugged in its 1800rpm when changing between (Manual) gears. When IAC is unplugged its 1000 rpm to 1400 rpm

Anyone know a part number or a correct IAC that works?

 

[lil_Blue_Ford]

If you tap on the IAC when it’s idling high, does it change RPM or stay the same?

I’ve had mixed success with IACs from Autozone, some work, and some don’t, but they are lifetime warrantied, so when they don’t work I just take them back for another.

I’m also going to question the computer. Yes, the ECU/ECM. They are notorious for the capacitors blowing and causing all sorts of chaos. I just pulled the one out of my one truck and opened it up to find all three capacitors blown and a couple resistors fried. No wonder it had issues.

 

[mark22elliott]

If you tap on the IAC when it’s idling high, does it change RPM or stay the same?

I’ve had mixed success with IACs from Autozone, some work, and some don’t, but they are lifetime warrantied, so when they don’t work I just take them back for another.

I’m also going to question the computer. Yes, the ECU/ECM. They are notorious for the capacitors blowing and causing all sorts of chaos. I just pulled the one out of my one truck and opened it up to find all three capacitors blown and a couple resistors fried. No wonder it had issues.

i pulled the ECU a few days ago, its correct for the car and everything else works. I have a spare thats fried, previous owner fried the spare, the one in it came from a running driving car. I could get it re-flashed but thats another $250 and significant time.

With the IAC off the car, KOEO, the valve strokes fully open and immediately snaps shut again as there is no flow. It looks like its working to me.

I havent tried tapping it, the spindle strokes open and closed, its new.

it has 2 pins, i dont know visually the difference between a stepper motor and a PWM solenoid, i doubt the autoparts stores know either, so a part number that works would be much appreciated.

Ive had no luck identifying a hitachi part as other forums have suggested?