1992 Ranger - Racing Engine Upon Startup?

[rangerenthiusiast]

Nah, Rangers are pretty simple trucks. At least you have some room to work and parts are cheap.

73-79 Fords will always be my automotive love affair. But the supply of affordable, unmolested, daily driver/work grade trucks are drying up quick. You either have trailer queen show trucks or purpose built rigs.

Funny thing is, 73-79, and 92-96 trucks, espicially nice clean 4wds, seem to be gaining value pretty quickly. I remember even 10-15 years ago you could barely give them away

I know, right? Everything I like that used to be cheap always goes through the roof in price the minute I get a little jingle in my pocket. Sigh.

Gotta say, the Ranger runs a thousand times better with that darned IAC unplugged! It now idles anywhere between 750 and 1100 RPM. Drives better, shifts smoother, just all around nicer to drive. Makes me wonder what the heck it’s doing there in the first place. I’m assuming that it will help a little with cold starts and may improve gas mileage a little when I get the new one in. But man, a bad one will make a truck run like poo.

 

[rangerenthiusiast]

Sooooooo... this issue is really annoying me. I’ve had the new Hitachi IAC on there for 3-4 days now (didn’t disconnect the battery to reset the computer, if it matters). Sometimes (especially when cold), the idle will be as high as 1700 RPM or so. Later, it seems to drop to 1100-1330 and sometimes even gets down to 800-900 (I’d be happy if it just stayed down there, but no). It almost seems like the lower RPMs are after she warms up a little, but then she will suddenly idle at 1700 again, even thought she’s warm.

Trying to determine if it’s likely that the new IAC is bad, or if the old one was fine and it’s just something else. If I can ever get a day off from work, I’m planning to do a little test that someone else here recommended, involving the IAC and “anti-diesel screw” and try to figure out if there are any vacuum leaks. Has anyone else had such weird idling problems? What happens if you just leave the d@mn IAC disconnected, since it’s so problematic?

Any help is appreciated, as this is really preventing me from enjoying the truck and moving on to other things that need to be done on her. Thanks.

 

[cp2295]

I’d honestly get a motorcraft IAC off rockauto, I know hitachi is the oem manufacturer, but they build it to motorcrafts spec, the aftermarket hitachi might not be up to par. Also i would definitely look for vac leaks.

Make sure your TPS Voltage is within spec too. There’s a write up somewhere on here


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[rangerenthiusiast]

I’d honestly get a motorcraft IAC off rockauto, I know hitachi is the oem manufacturer, but they build it to motorcrafts spec, the aftermarket hitachi might not be up to par. Also i would definitely look for vac leaks.

Make sure your TPS Voltage is within spec too. There’s a write up somewhere on here


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Any way to test the Hitachi for proper function, other than to just buy another and hope for the best?

Also, TPS? Sorry for the ignorance.

PS - Never did find out where the elusive “anti-dieseling screw” is located. Wondering if someone was pulling my leg...

 

[cp2295]

Any way to test the Hitachi for proper function, other than to just buy another and hope for the best?

Also, TPS? Sorry for the ignorance.

PS - Never did find out where the elusive “anti-dieseling screw” is located. Wondering if someone was pulling my leg...

Not sure of how to test the IAC.

TPS-throttle position sensor, just opposite of where your throttle cable hooks up.

Never heard of such a thing. I’ve heard of a throttle stop screw, which you shouldn’t mess with, unless you are adjusting the TPS sensor voltage, look it up on here.


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[rangerenthiusiast]

Not sure of how to test the IAC.

TPS-throttle position sensor, just opposite of where your throttle cable hooks up.

Never heard of such a thing. I’ve heard of a throttle stop screw, which you shouldn’t mess with, unless you are adjusting the TPS sensor voltage, look it up on here.


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Cool, will do. Thanks, man!

EDIT - I’m an idiot. Rusty already told me what a TPS was, but I forgot. Nervous system damage is a bitch.

 

[rangerenthiusiast]

Not sure of how to test the IAC.

TPS-throttle position sensor, just opposite of where your throttle cable hooks up.

Never heard of such a thing. I’ve heard of a throttle stop screw, which you shouldn’t mess with, unless you are adjusting the TPS sensor voltage, look it up on here.


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This is going to sound dumb, but how would I look up the TPS sensor voltage info on here? I’ve had a lot of people advise me that I can look things up here, but rarely have any luck finding what they’re referring to.

Thanks!

 

[cp2295]

This is going to sound dumb, but how would I look up the TPS sensor voltage info on here? I’ve had a lot of people advise me that I can look things up here, but rarely have any luck finding what they’re referring to.



Thanks!

Perform these checks with the key on engine off.

The input side should have 5v with the key on at all times (I believe it’s a red/gray wire). the reference side should have around .8v with the throttle shut and should raise smoothly as you open the throttle until it reaches about 4.8v full throttle. The remaining wire will be ground. The reference wire voltage should be smooth, no sporadic jumping or dips/dead spots where there is suddenly no voltage (or spikes for that matter).

I can’t remember which color wire each is, but if u follow that guideline it should be pretty easy to tell which is which.

To test that the ground wire is grounded simply set the ohm meter to 200 ohms and check continuity between that pin and chassis ground. Should be below 1 ohm.


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