I've got a couple questions - trying to sort out this truck.

So I picked up this truck fall of last year. She's in pretty decent shape, but she's got a few persistent problems I've been trying to sort out.

What I've done so far:
Fuel Pump (Delphi pump)
Fuel Filter (Motorcraft)
Plugs and Wires (Autolite and Motorcraft)
Coolant Flush
Tie Rods, Idler Arm, Pitman Arm, and Upper and Lower Ball Joint on the driver side
Both Front Wheel Bearings
Front Brakes
Fixed a couple small vacuum leaks
PCV Valve (Motorcraft)
Torqued Intake Manifold Bolts
Oil change and filter (of course)


Now the problems she's got:

High Idle on startup - as in ~2200 until warmed up. But only when moving. As in with the clutch in while coasting it'll stick around 2200 and only come down when I let the clutch out in gear (which is destroying my clutch) or when I come to a stop it'll slowly idle down to around 1500. When warm it'll idle at a stop around 1000 and 1500 when moving

I'm pretty sure the intake manifold has already loosened itself up again (in maybe 5k miles). Before tightening the intake, the truck would surge at high RPM's (maybe 4k or higher?), and afterwards the surging went away - but now it's back. I figure I'll just have to do it again and use loctite this time

Immediate loss of fuel pressure - Like as soon as you turn the key off, it drops to 5 psi almost immediately, and then trickles down to 0. 30-32 psi at idle, and 45 or 48psi (can't remember) if you unplug the vacuum hose from the regulator. I had thought it was the check valve in the fuel pump, since the fuel pressure regulator is working right and i can't smell any gas in the vacuum line, but I still lose fuel pressure. Upon further inspection, it looks like i do have a small leak in one of the fuel lines - not sure how to replace/fix it though. (see below picture)


(Ignore the text, I stole the first image I could find off google for approximately the right area) Pretty much right in this area here, just a little further down in the engine compartment. It's a braided steel hose into a hard steel line, and looks like its leaking right at the connection. How do i fix this? Do i just have to replace the whole line?

I've found a vacuum hose unplugged under the throttle body, and I traced it back to the carbon canister. I have absolutely no idea where it goes though, I can't see any connections where it would go.


Also, some asshole ran a yield sign a couple weeks ago and I t-boned him. Not too much damage, but he ****ed up my passenger foglight. Anyone have any clue what foglights these are and where to get another one?




I plan on checking the tps voltage, hopefully the TPS is what's causing the high idle - it should be around 0.9V right? I also need to check the CEL, I have a scanner but I need to clean off the connection on the truck first.

So any clue on the vacuum hose or the foglight? Does the TPS sound like the right place to start for high idle? (Previous owner replaced the IAC valve, looks pretty new)



Thanks for your help in advance!

I would deal with that open vac line causing an unmetered air leak into your engine before worrying about anything else related to a high idle. Even if you just plug it with a screw to see if that is causing your high idle issues and then worry about fixing it properly later when you have more time.

If you have a fuel leak at a connection it is probably just a bad o-ring, pop the line apart and inspect. Have a fuel-rated ring kit ready when you do. Also, THAT could be the cause of your loss of fuel pressure as soon as the key is turned off. A return-type system will loose pressure quickly, but your numbers seem excessive. A leak in any pressurized system will make it loose pressure, go figure right.

Right, sounds like a good plan of action. Though I checked the hose when I found it laying there and it has no vacuum - but I'm sure the port it goes on does. That's why I was hoping one of you ranger gurus knew where it might plug in

After engine is warmed up let it idle and unplug the 2 wires on the IAC Valve, valve will close all the way and idle should drop down to 500rpm or engine should stall, either is good it means no vacuum leaks.

If idle stays high then you do indeed have a vacuum leak, leave IAC valve unplugged and start removing vacuum hoses 1 at a time and then plug port with your finger, when rpms drop you found the leaking hose or device at the other end of that hose.

If idle does drop when you unplug the IAC valve then Computer is setting the high idle, could be ECT sensor, maybe TPS but a long shot on that.

One other thing, on the throttle linkage there is a screw that "looks like" an idle screw, it isn't, it is an anti-diesel screw, technically, but previous owner may have adjust this.
So with IAC Valve unplugged unscrew this screw to see if this is setting the high idle, i.e. holding throttle plate open too far, turn it until RPMs are at 500 or so, below 600.
Manual trans idle should be 625 when engine is warmed up, if throttle plate is being held open and letting enough air in for 750 idle then IAC valve can't do its job, even when it's closed all the way it can't get idle down to 625.
This screw also adjusts the TPS voltage at idle since it moves the throttle plate rod, which is connected to the TPS on the opposite side of throttle body.

The throttle plate is held closed by a spring, if spring gets loose then air flow can suck and hold the throttle plate open a bit, a long shot but still a valid target, lol.

Yes, spec for TPS when throttle is closed is .69 to .99 volts, under 1 volt
Test with key on engine off
Pierce Center wire with sewing needle to test this voltage
Open throttle all the way slowly, voltage should increase slowly, no jumping or dropping, at full throttle voltage should be above 4.5v, 4.50 to 4.99 is spec

Alright, so I figured out where the hose goes, there a port on the bottom of the throttle body with an elbow facing the firewall. Got that hooked up and found another vacuum hose that was dry rotted to shit, and I got the idle down to 750-800 with the IAC unplugged. Not where it should be, but definitely better than it was.

I got time to try and tackle the front diff pinion seal this weekend, but ran into some more issues. That pinion nut is tight!! I mean, like I had a breaker bar and a 5 foot bar on the end of that and I still couldn't break it loose! Any tips on that or any advice? While I had it up on the lift and was checking it out, I noticed the passenger axle seal was leaking, the stub shaft had play in the diff, and the u-joint was shot too! It's just one thing after another, but I guess I should've given it a better once over before I bought it.


The thing I really don't know about though, is there's a rubber seal on the front driveshaft, on what ford calls the universal joint yoke, that seals around a spring loaded ball joint with a needle bearing in it. If I'm remembering it right and looking at this diagram right, it's right here:


Mine is completely dry rotted and all cracked, and I can't seem to find any replacement part for it or any mention of someone replacing it. I guess if I have to I can just get a whole new driveshaft or yoke, but I'm not exaclty liking rockautos price of $300. Or I suppose I could hack it with hose clamps and a rubber boot from somewhere, but I really don't like doing that.

So nobody's run into this seal dry rotting and needing to replace it? I'm planning going to the junkyard and searching one that's all rotted and cracked, but I'm not hopeful :/

Quick reply here to bring this back from the dead.. I've been unable to find any vacuum leaks, but I just found out that the previous owner swapped to a manual trans but didn't switch out the computer.

Could this be causing my high idle? She idles around 900 now, that's about what automatics are supposed to idle at right?

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Also! I just had another thought. I know the manual computers will cut off fuel when you downshift and aren't touching the gas... I'm assuming autos don't do this? So I should see a pretty good jump in mpg when I swap right?

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All fuel injected engines turn off fuel injectors when coasting, one reason why EFI gets better MPG
When engine RPMs drop down to about 1,200 they will come back on but at idle RPM fuel flow.

With engine warmed up and idling
Unplug the IAC Valve's 2 wire connector
IAC Valve will close all the way and RPMs should drop down to 500, or engine may even stall, either is good, it means no vacuum leak

If idle stays the same then you have a vacuum leak OR..............someone has mis-adjusted the anti-diesel screw

On the throttle linkage there is a screw the "looks like" an idle screw, fuel injection of course couldn't use an idle screw, no Jets, which is why there is an IAC valve
So if RPMs don't drop check that screw, unscrew it slowly to see if idle drops, if not return it to where it was.
If RPMs do drop then continue turning until RPMs are at 500

Man you're coming in clutch with all this info on my threads tonight! Thanks!

So if my engine idles real low or stalls when I unplug the iac, the only difference I'll see by switching to a manual trans computer is an idle about 300 rpm lower and no more auto trans codes (even though they're non reporting)?

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