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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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  #1  
Old 09-20-2016
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1994 Ranger 4.0 intermittent bogging/sputtering

Hello, I recently bought a 1994 Ranger with a 4.0 and auto transmission. I bought it knowing that it had drivability issues. The previous owner told me (and I confirmed on my drive home) that it would run fine for 5-10 miles, and then it would start coughing, sputtering, and bogging to the point where you can only go 20-25 MPH. He said he replaced the crankshaft position sensor, coil pack, and removed the catalytic converters, but nothing helped.

I was able to make it the 25 miles home from where I bought it. When entering onto a fairly major highway, it started bogging down and sputtering, but I kept the same pressure on the accelerator, and soon it started running properly, and took off down the road.

This evening, I showed my father the truck (he was interested in seeing it), and it started sputtering and bogging down just idling in the driveway. The engine was bone cold. As it was acting up, I noticed that the exhaust seemed pretty strong, like it was pretty rich. Is there a way to check the fuel mixture?

I'm asking for help, as I have no experience with these engines.
Thank you in advance.
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Old 09-20-2016
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You'll have to start by putting the catalytic converters back in.
It may run OK with out them, but it depends upon where the Oxygen sensors are in the exhaust.
Overall, the cats. provide back pressure too and the whole system is designed to have them on.
With said, even with them in place, the problem most likely won't go away.

Clean your MAF (mass air flow sensor), there are special cleaners for this, be carful it's fragile.
Replace your air cleaner too if it hasn't been done for a while.

When the engine is bone cold there will be a smell of it running rich, even more so when then cats. are gone.

Not sure if it has a distributor, but if it doesn't there will be a coil pack, that can be a source of trouble as well as the wires and plugs.

Remove the plugs and post some photos of them _ they should be clean _ pretty much with bone white insulators.

Any service records or bills to show what any previous owners have installed ?
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Old 09-20-2016
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Thank you for your reply.

You'll have to start by putting the catalytic converters back in.
It may run OK with out them, but it depends upon where the Oxygen sensors are in the exhaust.
Overall, the cats. provide back pressure too and the whole system is designed to have them on.
With said, even with them in place, the problem most likely won't go away.
I don't have them, plus they were removed because they were plugged.
Clean your MAF (mass air flow sensor), there are special cleaners for this, be carful it's fragile.
Replace your air cleaner too if it hasn't been done for a while.

When the engine is bone cold there will be a smell of it running rich, even more so when then cats. are gone.

Not sure if it has a distributor, but if it doesn't there will be a coil pack, that can be a source of trouble as well as the wires and plugs.
Previous owner claims he replaced the coil pack (it looks cleaner than anything else around it)
Remove the plugs and post some photos of them _ they should be clean _ pretty much with bone white insulators.

Any service records or bills to show what any previous owners have installed ?
Truck was owned by a high school student who replaced some parts, and ultimately gave up on it. I bought it from the dad.
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Old 09-20-2016
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If the cats were plugged then it's been running rich for a while.

The MAF sensor is located right after the air cleaner and there are 4 or 5 wires coming out of it.
If you take off the air intake tube and shine a light on the sensor prongs, they should be shiny.
Start with the simple stuff, like wires, plugs and cleaning the MAF sensor.
Get your self a can of electrical contact cleaner and go through the engine bay and clean all the sensor plugs.
Clean your grounds.
MAF sensor is very important.
Crank shaft sensor.
Cam Shaft Position sensor (way at the back of the engine by the fire wall)
Idle air control valve (IAC) valve ( this is located at or near the main throttle body, your accelerator pedal cable will be near by.

If your not familiar with any of these, Google is your best friend.
Get your self a manual, they are pretty basic but, you can familiarize your self where things are located and the terminology.

Is there a CEL (check engine light) ?
Does it light up when you first turn the key on, maybe the bulb is burnt out ?

Don't be afraid to ask questions, we all have to start somewhere.

Last edited by Jeff R 1; 09-20-2016 at 11:28 PM.
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Old 09-20-2016
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Thanks! I'll do that.
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Old 09-20-2016
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Sounds like there is allot to go through here, but you have to start some where.
I won't wish you luck, it's just a matter of tracking down the problem(s) through elimination.
If the MAF sensor is dirty and/or has a dirty connection the computer (PCM) can't read how much oxygen is going into the engine and it doesn't know how much fuel to add to the injectors.
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Old 09-21-2016
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That makes sense.
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Old 09-21-2016
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Tonight I decided to clean the MAF sensor. I took it off and sprayed MAF cleaner in it, let it dry, and put it back on. I went out for a quick drive to see if it made a difference. It did not. It immediately started coughing and sputtering any time I'd press on the accelerator.

It stalled out on the street, and when I started it back up it ran better, but still surging occasionally.

A little later, I was leaving the gas station and it started coughing and sputtering again. This time I was able to keep it going around 15 MPH. Then all of a sudden it started running better again. Both times i drove it, the CEL came on after about 10 minutes of driving.

I was going to hook up my code reader, but I wasn't sure where the connector was.

Can someone help identify these? The second one looks like the diagnostic test connector, but I wasn't 100% sure.
Thanks.
1994 Ranger 4.0 intermittent bogging/sputtering-img_20160921_193901467.jpg

1994 Ranger 4.0 intermittent bogging/sputtering-img_20160921_193933515.jpg
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  #9  
Old 09-21-2016
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Where To Plug In Code-Reader?
I have no idea what those other plugs are though.
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Old 09-22-2016
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Check your plugs, if it's running so rich that the cat converters were plugged up, I'm sure the plugs are so fouled that it's causing misfires.
Probably one of the codes that's going to show up.
The plugs should be clean and pretty white.
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Old 09-22-2016
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This evening I replaced 5 out of the 6 spark plugs and plug wires (6th one is behind the A/C components, I'll have to get a swivel socket in order to change that one). I looked at each of the plugs as I took them out. The three on the driver's side were kind of a tan color, whereas the two on the passenger side were either brown/burnt, or soaked in oil. I replaced all 5 of them with new Autolite copper plugs, and good quality spark plug wires. I took it out for a test drive to see if it made any difference. None whatsoever. It still coughs and cuts out. I have noticed that when it bogs down (it acts like it's either starved for fuel, or it has too much), I can hear a popping sound coming from the engine compartment.

I doubt this is a good thing to be doing, but I've found that when it is doing its thing, if I pull over and disconnect a plug that goes to a metal cylinder on top of the intake, it stalls (previous owner said when he did it, it made it run better?). Then I plug it back in and restart it, and it runs as good as it ever does.

I'm still not sure what to try next. I can't find the diagnostic connector. I've looked under the dash and all along the driver's side fender, and can't see it.
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Old 09-23-2016
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Soaked in oil, are you sure it wasn't gas ? (if it was soaked in oil, that's a mechanical problem with the head)
At any rate that metal cylinder on top of the intake is your IAC valve (idles air control valve).
If it barley idles (500 rpm or less) or stalls when you unplug it, that's a good sign, it shows that you have no vacuum leaks.
The computer controls the idle through that valve by allowing more or less air into the engine.
When the engine is cold on first start up, the valve opens more to allow a faster idle and as the engine warms up, the computer slows the idle through this valve.
Unplugging it closes the valve off so there is pretty much no air flow into the engine and in your case, it stalls.
If it continued to run, that would indicate a vacuum leak somewhere.

I have a 3 litre 1999, so there are many differences where things are located.
Someone else should come along and give you a hand where the plug the code reader in.

You're also facing a bigger problem, most here start with a perfectly running truck and when something goes wrong, that makes it easier to diagnose simply because it was running well before.

With yours there is no history as what has been done to it, other then someone removing the catalytic converters.

I'm wondering if the oxygen sensors were removed in the process.
If that happened it will be impossible to get it to run correctly.

If it's like my 3 litre, there should be three, one for each bank (left and right side of the engine) and one further down the exhaust system
They'll be threaded right into the exhaust pipe(s) if they're there.
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Old 09-23-2016
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Quote:
Originally Posted by Jeff R 1 View Post
Soaked in oil, are you sure it wasn't gas ? (if it was soaked in oil, that's a mechanical problem with the head)

It may have been gas. All I know is it wasn't the proper color. Ha ha

I have a 3 litre 1999, so there are many differences where things are located.
Someone else should come along and give you a hand where the plug the code reader in.

You're also facing a bigger problem, most here start with a perfectly running truck and when something goes wrong, that makes it easier to diagnose simply because it was running well before.

I knew going into this that it would be a challenge, but the body isn't too bad (especially for Iowa), and I got it for a really good price.

With yours there is no history as what has been done to it, other then someone removing the catalytic converters.

I'm wondering if the oxygen sensors were removed in the process.
If that happened it will be impossible to get it to run correctly.

The oxygen sensors are still there. I just saw them today.

If it's like my 3 litre, there should be three, one for each bank (left and right side of the engine) and one further down the exhaust system
They'll be threaded right into the exhaust pipe(s) if they're there.

My truck only had the one catalytic converter after the Y-pipe.
Thank you for all the help you've provided so far. I know eventually I will get this thing running properly.
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Old 09-23-2016
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See this thread.

1994 B4000 4.0L V6 Camsensor - Ford Truck Enthusiasts Forums

I think your truck has a cam shaft position sensor, it will be at the back of the engine if it's there and in your case, will have a three wire connection.
What can happen with these is the shaft bushing wears out and the metal part that rotates in front of the sensor itself damages the sensor.
The sensor needs to be removed to see of any damage has occurred.
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Old 09-23-2016
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If it's at the back of the engine, how are you supposed to remove it? There's about 1 1/2 inches between the block and the firewall, hardly enough room to get my hands back there, along with a tool.
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Old 09-23-2016
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You don't have to pull the whole thing out, you just want to remove the sensor and inspect things for damage.
Being tall with long arms helps.
If your shorter, then some old pillows and a packing blanket in the engine bay will allow you to comfortably get back there. That sounds ridicules, but it does work.

I used this foot long extension with a socket swivel and a 1/4 drive adapter to get to mine.
I'm not saying that yours may be causing problems, but it can and it may be worth checking.

Someone may have even replaced it at one time and put it in wrong, there's been a few posts here where that has happened.
Mine more then 90 degrees out from where it was supposed to be.
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Old 09-23-2016
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Ok. I'll check that out.

I was also wondering about the fuel filter and the fuel pressure regulator. It acts like it's either getting too much fuel or not enough.
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Old 09-23-2016
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I would say it's getting too much fuel and I say that because the cats were plugged up and were removed.
That and your description of your spark plugs.

I think your fuel system is different then mine and that is the fuel continually flows to the rails and returns to the tank.
What causes too much fuel is that the injectors are staying open too long and/or are not squirting at the right time and/or dirty ( when they squirt, the atomization is not a fine mist).

The computer relies on engine temp, valve timing, compression timing.
How much oxygen is present in the exhaust, how much oxygen flows into the engine (MAF sensor does this) etc.

If one of these things are not working properly, the whole thing can run rich.

For the most part sensors don't fail, they become dirty and/or the connection becomes oxidized just enough where they can't relay information back to the PCM, unplugging them and plugging them back in is just enough to clean the contacts, but a contact cleaner should be used anyway.

I don't think the fuel pressure regulator is at fault, but pull the vacuum line off of it and if there is a strong smell of fuel, then it has failed.
If we're talking about the same device, I think the correct name is the "fuel dampener", the vacuum line is a safety feature in case the diaphragm fails, the fuel gets sucked into the intake manifold rather then being squirted all over the engine bay.

What the fuel dampener does is control the pulsing of the injectors at high speed.

Fuel Pulsation Damper

If it's leaking that would explain where all the fuel is going and why the plugs are dirty and the cats were plugged.
There would also be a drop in fuel pressure of course.

Last edited by Jeff R 1; 09-23-2016 at 01:16 PM.
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Old 09-23-2016
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1994 Ranger 4.0l and earlier didn't have cam sensors, only those sold in Calif. had to have them

1995 and up all had them.

Fuel pressure(fuel pressure regulator) isn't usually a come and go issue, and you would notice low pressure at highway speeds first as engine ran out of fuel during high demand.

High pressure won't effect anything since normal pressure is 35-45psi and fuel pump is only capable of about 60psi, and computer would just reduce open time of fuel injectors in any case in response to O2 sensors detecting Rich condition is exhaust.

Fuel pressure regulator(FPR) does operate using engine vacuum, which means if FPR were to leak, fuel could be sucked into engine via that vacuum hose..........cause rich running.
FPR is located passenger side top front of engine, you will see the Fuel Return line connected to it.
On the back side you will see the vacuum hose, it travels back under the coil pack and around the back of the intake then up to drivers side of upper intake where it plugs in to the Vacuum manifold, so vacuum hose enters on Drivers side of engine, so leaking fuel could effect drivers side more.
Remove this vacuum hose and check it for fuel or fuel smell, replace FPR if there is fuel in that hose, thats the problem.


1994 Ranger 4.0l will have two O2 sensors, one for drivers side exhaust(bank 2) and one for passenger side exhaust(bank 1)
I would pull out Drivers side O2 if those spark plugs looked darker color and blackish, and most likely replace it.
O2 sensors last about 150,000 miles after that they tend to cause engine to run richer.
O2 sensors use a chemical that gets depleted over time so just like a battery they do simply wear out.
So replacing both would be best idea, they actually pay for themselves in better MPG over the next 100,000+ miles.

1994 Ranger will use OBD1 so OBD2 scanner won't work, but very easy to get codes by watching Flashing CEL(check engine light) after putting computer into Test Mode.

Short video of how to do that here: www.youtube.com/watch?v=X07hu0kAuzE

The Codes may help alot for this.

It reads like computer is either getting bad information from sensors, or computer itself is the issue.
Cleaning MAF can restore good information to computer
Cleaning IAC valve can give back good Control of engine to computer
New O2 sensors can give back good info to computer
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Old 09-23-2016
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Thanks Ron !
The missing info that was needed.
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Old 09-23-2016
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Thanks both of you.

Ron, I have an OBD1 code reader for EEC IV (my '85 Thunderbird also uses EEC IV), but what you're saying is that there isn't a connector on this truck?

I will check the codes this evening and let you guys know what I find out.

BTW, it is the passenger side spark plugs that are fouled. One is pretty brown and crusty, the other one is dark and wet. I haven't gotten the third one out yet.
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Old 09-23-2016
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EEC-IV OBD connector is in the engine bay usually driver side near firewall or near engine fuse box, will look the same as the t-birds.
May have EEC snap on cover as shown in video, just follow main engine wiring harness it is part of that.

Still check the FPRs vacuum hose.

Also here is another test to try
Press gas pedal all the way down, and hold it down
Turn on the key
Now try to start engine, keeping gas pedal all the way down

Engine should NOT start, should not fire at all
Fuel injectors should be shut off if TPS(throttle position sensor) is sending 5 volts to computer BEFORE cranking engine.

If engine fires or starts, then try this
Start engine and let it idle for a minute then shut it off
You changed the coil pack so you know where the 4 wire plug in is for it, unplug that connector, so no spark.
Now do the same test as above, gas pedal to the floor and hold it down.
Definite no start this time, lol, but keep gas pedal down and crank engine two times counting to 5 each time.

Not turn off the key and pull the 3 spark plugs on passenger side, they should all be DRY, no fuel on them, if one is wet then its injector is leaking.
Check drivers side as well.

If all the plugs are WET then you may have a stretch throttle cable so are not getting full 5 volts to computer from TPS, which is why engine started in first test.

Google: Ford ranger throttle cable mod

That will restore full throttle, giving you back better performance, and allow you to do the above test.

All Fuel Injection computers have a Clear Flooded Engine routine, not just Ford, most are the same as Fords
Hold gas pedal down to the floor, turn on key, then try to start, should get a no start because injectors are off, but spark is still on.
As soon as gas pedal is released injectors will start up again, even while cranking
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Old 09-23-2016
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Truck didn't start with pedal to the floor, so the TPS is good.

I replaced the fuel filter as well, but it didn't change anything. Tomorrow I'm going to check the FPR vacuum line, and drive it around and get it up to operating temp to check diagnostic codes. If both of those turn up no results, I don't know what's next.
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Old 09-23-2016
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Computer would be next but getting the codes might give you a clue if computer is the problem.

1994 will use 3 digit OBD1 codes, they tend to not make sense or you can't get the codes if computer has a problem.
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Old 09-23-2016
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I hope I can retrieve the codes. I have a book that came with the code reader to tell me what the codes are.

If can't retrieve the codes, what would my next plan of action be?
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