'99 Ford Ranger idles too fast

gary__March 16, 2006

My son has a '99 Ford Ranger 4x4 with a 3L v-6 flex fuel engine and an automatic transmission. He says when he first starts it up it idles too fast, slows some but still idles too fast for a while. When it's fully warm he says it's ok. He lives in the same town he works and doesn't drive far to work so it sounds like the brakes are getting a work out.

I don't know anything about his truck, don't have any manuals or anything to tell me how it works. Does that symptom ring a bell with anyone? I'll take a look at it when he comes for a visit this weekend or the next, but aside from checking for linkage and cable problems, I don't know what else I could do for him. Our Tempo idled too fast when the IAC went bad, but idled fast all the time. Any ford experts out there have any idea's? A good active ford forum might help if you have a line on one.


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I don't know what the linkage looks like on the ranger, however I recently had a problem with the throttle sticking on an F-150. I got some throttle body cleaner and cleaned out the linkage and the butterfly pivots. It worked fine. HTH

    Bookmark   March 16, 2006 at 10:23PM
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could be a combination of problems. first though, if this car is new to the owner, he may just not know how it normally runs when cold. most cars have a fast idle on startup. and then drops out when warm.it could also be worn out throttle body bushings, that seal better after warmup. try spraying wd40 around the throttle body when it is cold and running fast. the wd40 will cause the car to rev when it is sprayed on a leaking intake spot.

    Bookmark   March 17, 2006 at 2:21PM
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He's had it probably about a year or so. This is definately a new trick the truck has developed and is not a normal condition. It's a '99 and doesn't have enough miles on it, 70k to 80k miles maybe, for anything to be worn that much.

I'll try spraying stuff around and see what happens. Never had much luck with that approach myself dating back to my carburetor days. Seems like spraying an accelerant just about anywhere under the hood is enough to change the idle sometimes:)

He didn't make it here this weekend anyway due to snow and ice in the pass, so keep the idea's coming. Maybe a trip to the library is in order in the mean time.


    Bookmark   March 18, 2006 at 12:05PM
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Your success with solving the high idle complaint will come easier with a good plan of attack. The first thing to determine is whether the high idle is caused by a mechanical issue, such as a faulty IAC, or a throttle plate that is not closing, or if the idle speed is actually being commanded high by the computer. One of the easiest ways to do that is to simply unplug the IAC with the truck at idle, and allow the engine to slow to the "minimum air rate" or base idle speed. There is no published spec, but if your minimum idle speed is in the 500-600rpm range in park, thats close enough. There is no normal service adjustments required, but if something is keeping the throttle plate from closing, then you'll have to correct that.

Most likely, when you unplug the IAC, you will find either a normal minimum idle, or no change at all. If there is no change, and the throttle is not sticking open, suspect air is getting around the throttle plate, which could be a bad IAC, because thats exactly what it does, it allows air to enter the engine around the throttle plate. Normally the computer has complete control of the IAC, but it can fail mechanically, so it must be checked.

The last senario has the idle speed being correct when the IAC is unplugged, and then going back up when it's plugged back in. this would suggest the computer is actually commanding the idle speed high. The questions from here are, is the computer getting a high power steering pressure input? Is the TPS spiking low, causing the computer to think the engine is at part throttle? Is the ECT, or IAT reporting to low of an engine temperature? This is where the correct scan tool becomes so important, because it allows the person trying to fix the car to see this information right from the computer.

    Bookmark   March 18, 2006 at 5:06PM
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Thank you john g. As usual for you, a very educational post. LOL, unplug the IAC. Sounds so logical and obvious, yet I don't think I would have thought to do that on my own in a million years. Wish I would have thought of that a few years ago while I was melting the rotors off my Tempo on the way to work one day. I'm such an idiot sometimes.

I'll do what you suggest and see what happens. If it gets down to requiring the scan tool to complete the diagnosis, I'll tell him he has to take it to someone who really knows what he's doing.

My son's a good kid and a hard worker but he doesn't earn a lot of money yet. I'm not sure he makes enough to cover his bills without dipping into his savings so I like to help him anyway I can. All I can do is all I can do though I guess.

Thanks again. I appreciate the knowlege and experience that you share.

    Bookmark   March 18, 2006 at 11:21PM
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Your welcome Gary, and thank-you for the kind words.

The thing people need to know is the experience and knowledge shared by many auto technicians is hard won. What may take me five to ten minutes to do when I walk up to someones car may have taken me years to actually learn. Thats a value that is easily overlooked by many, and flat out not respected by a few. The sting of dealing with the few sometimes flavors my responses on these posts (VBG). I do try to work on that more than I used too. VVBG

When it comes to dealing with car troubles, think about what I said about the IAC controls on that truck, and now compare that to the theft deterrent problem I am currently diagnosing in the shop. The BCM (body computer) is never powering down, and I have to determine if thats because it's getting a false input that makes it wake up, or if it is just faulty. There are 20 odd inputs that can wake up a BCM, and it takes twenty minutes for a BCM to go to sleep. So I have to monitor each signal for up to twenty minutes for some type of a glitch. The worst part is this truck has been worked on elsewhere several times in the last year for theft deterrent issues that have never been resolved. But they never brought it to me until it dies and would not restart Friday. Oh, the reason it would not start Friday? Corroded battery cables. The Theft deterrent complaints? They are directly addressed by a TSB I found. The BCM problem is on top of both of those issues! I'd welcome your fast idling truck as a chance to come up for some air!!! :)

    Bookmark   March 19, 2006 at 7:47PM
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Gary and John:
I sell at a small lot.
I loved reading the exchanges between you two because,

A: Gary is honstly trying to find some thing out and isn't trying to second-guess anyone--
And, B:, John is being very forth-right and keeping the technical terms as simple as possible.

Having a good mechanic makes all the difference in the world, and probably keeps a number of folks from winding up in a psychiatrist's office!!

In honor of John, I will today drop off a 12-pack at Matt's Garage here in town before 5 PM. I do this every now and then because I'm so grateful for always being treated so fairly by him---esp. when the boss is in Fla. for the winter.
(The boss is old-fashioned and thinks Matt's $50/hr. shop-rate is too high--the boss has had to eat his views time after time; but then forgets how much money he's wasted trying to do it through some jack-leg he knows! LOL!)

    Bookmark   March 20, 2006 at 12:43PM
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Kid finally made it home and of coarse his truck idled normally when we wanted to check it out. He lives at 4000' altitude and it's only 500' or so here. It was also 55 degrees here and it's been below freezing when he starts it at his place so I suppose either one of those things could be a factor.

Gave his truck a quick look and found it needs brakes all around and an axle seal. Gave him a list of parts to bring next time so I can fix those things. I can see the fun of being a dad never ends :)

    Bookmark   April 3, 2006 at 7:48AM
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our 99 ranger died a week or so ago, we were able to FINALLY charge the battery enough to get it home. Without being car minded at all, all signs pointed to batery, or alternator.. bought the battery.. tested the alternator which was good...
My brother figured the problem was the corroded cables, he cut them down and replaced the clamps.. worked great for a few days. THe battery meter had been staying at right below the full charge point. Today it dropped nearly all the way back down to the red, the radio went off again. Where should we begin to look for the problem??

Also... the other gauges are beginning to die off.. over the past few months. We lost the odometor, and the speedometer was reading AFTER 10 mph for a while... that finally completely died... any thoughts about that as well???

    Bookmark   August 3, 2007 at 2:46PM
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