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1997 Ranger throttle ghost

I have a '97 Ford Ranger, 6 cylinder. The stuff below only happens during the winter in Dallas which are not all that cold.

  1. The throttle has stuck open at about 45mph is 4th gear and would not slow down.
  2. On cool mornings the truck starts fine and the idle is fine. The engine warms up and the idle slows to normal. I go into the hardware store for 30 minutes and when I come out it is a little hard to start but it won’t maintain the idle speed and the engine dies. After a mile or two it is OK again. The temperature gauge on the dash shows the engine temp has fallen about half way from its highest to cool. This does not happen in the summer even though all the other indicators are the same. The engine temp can fall by 1/2 but the idle works so the absolute temperature of the engine can’t be it.

One time it never fails is when I take it to the shop and ask someone a lot smarter than me (and there are a lot of them) to check out the problem.

When it stuck open the shop thought the cables just needed a little lubrication but that did not appear to be the case and they could not duplicate the ‘stuck open’ problem.

Any help would be appreciated. The vehicle has about 110K and runs fine the rest of the time.

Re: the stuck throttle, I suppose a new throttle cable wouldn’t hurt and would bring some peace of mind.

You don’t say which 6 cylinder engine you have. The V6 4 L engine anyway sports an idle air control device that is used by the engine computer to set the idle speed. From what I can see that gadget controls the cold engine fast idle, hot engine idle boost (to increase the water pump flow presumably) , and to adapt for idle loads like AC turned on, alternator load, automatic transmission, etc. That’s a good suspect for your problem.

From what I see, when that device stops working it is supposed to throw a diagnostic code, so check for codes. It can’t be cleaned or adjusted from what I can tell. The testing procedure is likely in the shop manual, and might be in a Haynes or Chiltons too. Some of those gadgets have a diode in them that can fail, and that failure mode can be tested for.

If you are in a guessing mood, you could just replace it and hope it cures your problem. Probably costs around $150 for the part.

the throttle cable could be the problem too of course. But usually you can manipulate the throttle from the engine compartment and tell if it is sticking or not. My Corolla is older than your Ranger and has a cable for the throttle, and it has never caused any trouble in 25 years. I have lubed it where it exits the sheath on the throttle body a couple of times over the years I guess. I’m guess the cable isn’t the problem. If it isn’t the IAC gadget, more likely the throttle valve itself is gunked up and that’s causing it to stick. Best sol’n for that is to remove the throttle body and clean the backside of the throttle valve of all the gunk and soot that has accumulated from the egr and pcv systems. I’ve had to do that on my Corolla before. On the Corolla anyway, not a big job.

When I took it to the shop we talked about that and they could find nothing
wrong with the cable or any of the connections. That was their first
thought also but, in the end, couldn’t find anything. It has been there
twice (once for ‘stuck open’ and once for not maintaining the idle speed
when the engine is half-hot. In both cases they couldn’t find anything.

It is an experienced shop and, in fact, the guy just retired so he had many
years of experience behind him. It happens very infrequently. It must be
something just “on the edge” of failure if it is so sensitive to
temperature but if heat expands things why does it not happen more at hot
than half way inbetween? Why is there some point, inbetween the
temperature ranges, that shuts off the higher idle speed? I don’t really
understand the mechanism that regulates the idle speed so I’m kind of
shooting in the dark.

I tend to agree with your point that a new throttle cable might not hurt
and that might be the next step next winter when this shows back up again.
In any case it is an interesting issue, if just from a scientific point of
view. Thanks for the input.

I’m going to go with the idle air controller. Whether it’s the 3 liter or the 4 liter they both have it, and IAC’s are very common for failures on these Fords.

1 Like

The engine is the V6 4L and I like your comments about gunk in the throttle
valve. The affect of gunk could be very unpredictable and should change
with temperature. A failing diode should be a ‘one-shot’ deal and when it
failed it should should not recover so the failure mode should be

Where the gunk is concerned the engine is hot all the time. It is hot when
I come home and the gunk should be soft so it all goes back to normal.
When I start the truck in the morning the gunk has simply cooled off but
the valves must be in the right position to set the idle at the right
"starting" speed. As the gunk warms up it may become less sticky and, at
some point, not allow the valve to move. Only when the gunk gets hot enough
does it allow the engine to operate properly. The 3-mile trip to Home
Depot is not long enough to allow everything to heat up to the maximum
amount and 30 minutes later the gunk is now cool enough to stick in the
position it should be in at hot.

I have no idea if all that makes sense but it is something would fit what I
am seeing. Thanks for then information and suggestions.

I am no mechanic and will ask the guys at the shop to check what you say
the next time that happens. At 20 years old the truck keeps coming up with
problems and I am sure I’ll have an opportunity to visit those guys in the
future. My current worry is the transmission which is getting harder and
harder to get into 1st gear. The only sure way to get there is to shift
into 1st at the last minute before stopping at the stop sign. Wait for a
complete stop and you might have the guy behind you honking, thinking you
are on your cell phone.

Again, thanks for the tip. It makes sense to me.

Thanks, Pete, the fact it is a common failure is helpful.

I’ve had that same problem on my Corolla manual M5 transmission a couple of times over its 25 years. A new clutch master cylinder fixed it both times. Check the clutch fluid level first of course. If the fluid level is ok, and it shifts into first or reverse only after pumping the clutch pedal a couple times, that’s a big clue the clutch MC is the problem. After a while the internal seals on the clutch MC start leaking and the leaks prevent the build up of enough hydraulic pressure to push the clutch pressure plate hard enough to release the clutch disk, so when you try to shift you are battling with the engine’s flywheel.

I have the sense that you don’t have much wrong with your truck OP. Not anything that a little routine fixing and maintenance won’t solve. I’m predicting you drive on the conservative side and are pretty good at keeping the basic oil/filter changed and checking the fluid levels.

Thanks George, what you say makes sense. I do drive conservatively (and
treat all power equipment the same way - my thought is nothing is made to
run flat out for very long) and do regular maintenance. I’ll check what
you suggest but the through process you have gone through makes a lot of
sense to me. Thanks.

George --what if I put the truck in, say, 3rd gear and (after depressing
the clutch) put a brick on it for an hour or two. Then come back and start
the truck. If the transmission was engaged would that prove your point?
If the master cylinder is leaking the truck should try to move. Trying
this in my garage is probably not advisable.

I don’t know whether that would be diagnostic or not. All MC’s leak internally a little I expect. The pump-the-pedal test is how I diagnose that problem. If pumping the clutch pedal a few times allows it to shift easily into gear, and not pumping prevents it from going into gear, that’s the clue I use to replace my clutch MC. For me it has always started out hard to get into 1st and R when the problem first shows itself, but eventually becomes hard to get into 2nd, then a few weeks later, 3rd becomes difficult to engage … etc.

Good points. I am experiencing what you did. Hard to get into reverse,
then hard into 1st. It is following the pattern you describe. I’ll pump
it and see what happens.

Thanks for your advise. It makes sense to me - - I’ll give it a shot.

GeorgeSanJose - - I took the car to a shop and they checked out the master clutch cylinder and could not find any leaks anywhere. They suggest a new clutch and clutch plate at around $750. For that I can live with the problem a little longer.

But – what about the synchro gear? While the truck is rolling, all the gears are moving and it works just great. When it stops, however, getting it into gear R&1) is very hard. Is there a way to check the synchro gear? I hate to replace a clutch and plate and have it turn out to be something else.

Any suggestions?

I doubt that is a synchro problem. Not a common thing to have a synchro problem in 1st or R, due to the slow speed shifting in those gears. 3rd, that’s a synchro problem gear. Suggest to wait on that theory until after you’ve replaced the clutch. When you say they couldn’t find a leak, I presume you understand the type of leak that causes the problem for me anyway is not visible, nothing leaks that you can see. It’s an internal leak inside the clutch master cylinder.

They seemed to say (and I’ll make sure when I pick it up today) that they
were checking for external leaks although, when I left it I talked about

If you don’t think it is the synchro and (if it is not the an internal leak
in the master) then does that leave the clutch because there is nothing
else left to cause the problem.

At $750 for the clutch I tend to think replacing the master might make
sense if your choice of two unknowns are a cheap one or an expensive one.

As a diy’er I’d replace the clutch master before considering replacing the clutch with your symptoms. I can’t speak to your Ranger but replacing the clutch master cyl on my Corolla is maybe a 2 hour job, parts cost is less than $50. Not much to lose going that route in other words. Also you’ll be sure the clutch hydraulics are properly bled, as that is part of the job. Worse case, you’ll still have to replace the clutch, and probably they’d replace the slave at the same time, and then you’ll also have a new master, slave, and clutch and be good to go for a long time. Best of luck.

This is probably obvious, but before doing anything, be sure to check the clutch pedal free play is correct.

Thanks, George, I’ll give what you say a shot. Even if it turns out not to
be the master then, as you say, I have change out a 20 year old one for a
new one. I plan on keeping the truck for a long time. It fits the garage
with some walking room, carries the amount of fire wood I need, and the
rack for the kayaks fits perfectly (not to mention the 20 mpg I get in

Again, thanks for your help. I’ll let you know how it comes out.

If you’re going to diy, I found the following tool very helpful for that job on my Corolla. The clutch MC is in an awkward to reach corner, and tightening and reaching the fasteners and the hydraulic line connections can be pretty frustrating.

To get add’l working space, I had to loosen and shift the brake booster away from the clutch MC a little as I recall.

George, thanks for the information but DYI is going to have to include a
carpool buddy and I need to talk to him. I am now retired but he is still
working but probably the nicest (most helpful) guy you could meet. Spends
much of his free time helping down and out folks.

Most likely I’ll just pay somebody to do it.