As the title says, i have a 1994 Ranger, 2WD, 4.0L, 5-speed that has been gradually getting worse over the last few weeks.
The truck has 101k miles and it's pretty well maintained as far as tune-ups go.

Here is what i am dealing with: At idle, truck not moving - everything seems normal. RPM are stable, engine does not vibrate or shake more than usual. It feels the same as it did 3 years ago when i got it from previous owner.

The problem: When truck has not been driven for awhile, when accelerating or taking off from a stop, i can feel that the engine does not run smoothly and i can sense some roughness transmitted to the chassis. It feels like there is excessive engine vibration during slow or hard acceleration. What really bothers me is that as soon as i shift into second gear and i step on the gas (not floor it, but start to accelerate) i can feel that the truck is underpowered and that it starts to misfire, hesitate and even shake. It feels like it cuts on and off randomly.
If i happen to up-shift to 3rd gear a bit earlier and step on the gas, it misfires and SHAKES even worse and it feels extra sluggish! On 4th and 5th gear, this happens even more often and the shaking & misfiring are worse. Sometimes, i cannot even drive it on 5th when on the freeway because it shakes/misfires and it cannot accelerate to highway speeds and keep up. I am forced to keep it in 4th gear in order to do 65-70mph.

=> Another important symptom i noticed that is very disturbing is that sometimes, on 3rd gear or 4th, when i feel that truck is very underpowered and i floor it, it hesitates even more, shakes and i can hear & feel an audible"knock" or "detonation" somewhere seems like it's under my feet. Sometimes it does 2-3 or 4 detonations or audible "booms" in a row, until i back off from the gas.

=> The interesting thing is that once the truck warms up and has been driven for some time, the misfire, hesitations, shaking and overall sluggishness almost go away. It does not run perfectly but it is a lot better and smoother than it is when i drive it for the first few miles. It will still occasionally hesitate or misfire under hard acceleration. Unfortunately, over the last week, even when the truck warms up, it is still acting up.

So, what could be causing all this??

Here is what i have done so far to troubleshoot this with NO success:

1. Pulled OBD codes with OBD I Ford code scanner and only code i got is "214" which i've seen on and off for the last 3 years. I am 99% sure it is not related to this new misfire issue. Code 214 is Cylinder ID fault and i was never able to get rid of it. Again, i had this code 214 well before the misfire started. No other codes are stored in memory and the OBD I system seems very limited when it comes to diagnosis. It does not tell me which cylinder is misfiring.

2. I replaced all 6 spark plugs with properly gapped Autolite Platinum spark plugs. I installed new spark plug wires as well, few months ago. It made no difference.

3. I just replaced the coil pack with a brand new one (no brand name) that i got from Ebay. It made no difference compared the OEM one.

4. I got a spark tester and checked all 6 spark plugs for spark - all 6 tested good.

5. I cleaned the MAF sensor with MAF cleaner. It made no difference.

6. Air filter, PCV valve, and fuel filter are new. Made no difference.

7. Visually i do not see or hear any vacuum leaks, broken vacuum hoses, etc.

8. One of the oxygen sensors has been replaced in the past, since i see that it is branded Bosch and the other one is OEM Ford branded. I am not sure if a bad Oxygen sensor will cause such major misfire and/or detonations under load & acceleration.

9. This "problem" is gradually getting worse. The truck is driven very little since it is a third car and i use it only for weekend yard shopping trips. What started with minor hesitation and occasional misfire a year ago, is now happening 90-95% of the time. The truck is still drive-able and it starts every single time, does not die on me at stop lights and idles well. However, the loss of power is very obvious, the hesitation and misfires are common and the knocks/detonations are pretty loud under hard acceleration on 3rd/4th gear.

Given everything i listed above, what should i do next to diagnose and fix this?
Aside from the spark plugs and coil pack, what could be the next 2 or 3 most likely reasons for this problem? Injectors? Fuel pump? Catalytic converter? Bad MAF? Computer?
I cannot afford to buy brand new parts and try replacing everything on a truck that is worth $2k. This is why i want to start with the most likely areas first.


Thank you in advance for any input!
Dan

 

Here are a couple of simple things to try.

You can check to see if the fuel pressure regulator is working. It is located on the fuel rail at the front-right corner between the upper and lower manifolds. Pull off the vacuum line on it to see if there is fuel in there. If so, the diaphragm is leaking, and it's sucking raw fuel into the intake manifold.

Get a fuel pressure gauge to check the fuel pressure on the fuel rail. There is a schrader valve near the fuel pressure regulator for this. You need to pull out the valve core to install a pressure gauge, and the pressure should be about 35-40 psi. If it's lower, then either the fuel pump is dying or there are obstructions in the pressurized fuel lines.

 

Thank you for the suggestions.

I did check the vacuum lines that go to the fuel pressure regulator, to the EGR valve, etc and they all look DRY and healthy. No cracks, no gasoline spots, no weird gas smell.
I am planning to get a fuel pressure gauge tomorrow and measure the fuel pressure at the fuel rail.
If i have a bad fuel injector, this gauge won't help me much, will it? It will show the overall fuel pressure on the fuel rail but it will not show me if i have a specific bad injector?

==> Another question i have is related to the CAMshaft position sensor. I have been getting OBD I code #214 (Cylinder ID fault) for the last 2+ years but the truck seemed to run very well, despite the check engine light being always ON. I replaced the cranckshaft position sensor a year ago but it made no difference for the code. I still get 214. The only other sensor left that can cause this 214 code is the CAMshaft position sensor. My truck is 1994, and many Ford/Mazda documents state that 1994 should not have a camshaft sensor and only 1995+ have it.

My 1994 truck (built 11/93) HAS such sensor. I saw it and even took a picture of it. It's by the firewall and very hard to get to. It's a California truck, so maybe they put a 1995 4.0L engine in it. Who knows?!?! I am planning to buy a 1995 Camshaft position sensor and replace mine. I hope it fits since these things are not cheap.

As a side note, when i used my OBD I scanner and tried to run an "engine running" test to find mode codes, during the testing the OBD scanner tells you how many cylinders it is testing and it always shows "4" on my truck. I have a V6! Isn't this strange? Why is the scanner seeing only 4 cylinders on a V6 engine. Maybe that 214 code is the reason for it.

Could a complete failure of the Camshaft position sensor be the reason for all my truck's misfiring, hesitation, engine vibration and loss of power??
My idle is still stable and the truck starts every time. It's only acting up under ANY acceleration and load. It's is getting worse by the day.

At this point i am leaning towards: a) bad Camshaft sensor, b) bad Catalytic converters, c) Fuel pump or injector. Am i missing anything else more obvious?

Thanks!
Dan

 

If you have a clogged fuel injector, you will definitely feel the dead cylinder as a miss. It happened on my car, and it was a very constant miss, especially when trying to run at higher speeds.

I think the camshaft position sensor is installed in the hole that the distributor normally installed into. I've never had a car that had one, so I don't know for sure.

If you suspect the catalytic converter being clogged, you can disconnect it to see if the engine runs better. Of course, it may be hard to tell with all the noise.

 

Any suggestions on how to pin point which injector may be acting up?
Any way i can test them one by one?

Thanks!
Dan

 

On the later 4.0L engines that use sequential fuel injection, I think there is a test that you can run that will in sequence shut off each injector. But I don't know if the Ranger 4.0L engine got SEFI the same time that Aerostars did (1996?).

You can't remove just one injector to clean it out. In my case, I had debris clogging my injector, so I had to take them all out to clean them. I used carb cleaner to soak them, as well as a battery to activate them while I reverse flushed them with the little straw on the can of the carb cleaner spray.

You can try something I did to try to clean the injectors without removing them: I got a can of those tire inflater/sealers for its spray cap with a Schrader cap. Then I got a can of carb/injector cleaner that has a spout that the tire inflater spray cap would fit (Gumout does not, so you have to try different brands at the auto parts store). I removed the core from the Schrader valve on the fuel rail, and attached the tire inflater hose to it. That little cap may have a rubber gasket that you want to remove first; It can not stand up to the carb cleaner solution, and can break down and get into the fuel rail. Then disable the fuel pump; you can unplug the pump, or its relay, or the inertial shut-off switch. Attach the tire inflater cap to the can of carb cleaner and start pumping ("spraying") the cleaner fluid into the fuel rail. You should have enough pressure in there to start the engine, then continue pumping the cleaner in. The engine may die if you don't keep up, but just start over. After you've pushed about 1/4 or 1/2 of the can, it should have cleaned up deposits in the injectors. This is a lot more effective than dumping a can of cleaner fluid in the gas tank, as it's not diluted. If that doesn't work, you may have to pull them out to clean them as I did.

 

OK, so i tested the fuel pressure today, using a new fuel pressure gauge i bought.
Here are my numbers, let me know if they seem low and out of spec.

Ignition ON, Engine not running - 38 psi
Engine running, @ Idle - 31 psi
Engine running, RPM at 2500-3000 - 29 psi

The only time i got above 35psi was when the engine was OFF and the ignition was ON.
Are the 31psi and 29psi numbers major reason for concern and are they a SURE sign that i need to replace the fuel pump??

My fuel filter is less than 1000 miles old.

Thanks!
Dan

 

Those running pressures seem to be at the low end of normal. The spec is 40 PSI max, and 35 psi at idle when the manifold vacuum is applied to the back of the regulator. If you pull the vacuum line while idling, the pressure should go up to 40 psi. The other way to tell if you have a weak fuel pump is to drive the car under heavy load, such as accelerating up a hill, and see what the pressure drops to. It should not get below about 30 psi. That it holds 38 psi with the engine not running indicates that the regulator is working.

Having said that, I will mention that one of my fuel pumps died rather suddenly, and the only sign before it went was that the engine started to knock on uphills. I guess that was because the fuel mixture started to get lean as the pump weakened. I happened to be on the freeway at the time, so I don't recall what it behaved like during in-city driving leading up to that time.

 

Hmm... i am starting to think that the fuel pump is not the reason for my truck's hesitation, misfires, detonations and loss of power.
I agree that a failing fuel pump will show some more clear warning signs or will die rather quick. I've had two bad fuel pumps on German cars in the past, and both of them did not last more than a few miles after they gave me the first bad signs. There was noise, no-start issues, major hesitation, etc. My truck does not show these symptoms, plus the pressure numbers from today are not that bad.

Now i am really suspecting the bad injector(s) or bad Catalytic converters. Trying to decide, which one of the two is easier to tackle and test.

I got a set of 6 refurbished fully tested injectors today. I should have them next week but i am trying to figure how easy/hard will be to replace them.
It may be easier, while i am waiting for the injectors, to remove the cats, drive around and put them back on.

Replacing the CAMshaft position sensor and eliminating that stubborn 214 OBD code is also important but the sensor will cost me $400 + it's very hard to get to and calibrate the new one. I rather avoid this one for now.

Thanks!

 

I think pulling the cats off is easier than pulling off the upper intake.

If you plan to replace the injectors, get a replacement intake manifold gasket set. Fel-Pro makes a complete set, but I don't remember the part number. I got this set when I replaced mine:

https://picasaweb.google.com/lh/phot...C6x0pFnVRxA4Uw

which includes valve cover gaskets and the lower intake manifold gaskets, as the stock versions ALWAYS leak. Check out the other pictures of my replacement:

https://picasaweb.google.com/lh/phot...N3aOOMSWSksGNg

 

Have your ignition control module checked, I do remember some of them causing misfires

 

The 4.0L engines of that vintage used the EDIS, which was not as prone to failure. But it's worth checking as well. One thing to note is that each coil in the pack fired two cylinders, so if one coil, or driver from the EDIS module was bad, two cylinders would misfire or go out.

 

Did you ever find a solution?

 

I've had a similar problem with my 2003 ranger 4.0 5spd with 4 whl drive;
replaced plugs, plug wires, coil pack. Truck has 160,000 miles all oil changes
and drive train run with synthetic oil. engine-Mobil 1, drive train Royal
Purple.No leaks or use of oil anywhere.
I started using "Sea Foam" fuel additive every third tank of gas, cleared it
up. Apparently dirty injector or injectors from a bad batch of gas.
I've also replaced fuel filter multiple times, especially after the miss fire
started.
I religiously now use TTG regular unleaded gasoline. (Top Tear Gas)
best tested/rated supplied gas you can purchase. Not all gasoline is equal,
get the good stuff..
Shell oil publishes a listing of all TTG gasoline sources, of course Shell is
one of them..

 

Based on the age of the gas in my rig, has quality and contamination are highly likely. I just didn't want to drain the tank.