94 Ranger hesistation/misfiring help?!

DroidTN · Jan 25, 2014

Hey guys, I have a 94 Ranger XLT. I just bought it a month or 2 ago and the previous owner didn't know much about it. As far as the engine goes, it looks like it has a '95 Explorer engine, 4.0. You can check the pics out below and maybe help me identify what is in it. The only reason I say it is an Explorer engine is in one pic its written on it.

As far as my problem goes.. It just started a couple days ago, just running rough, at idle low speeds and high speeds. It idle a little below 1k. It seems like its getting a varying amount of fuel or misfiring. Sorry my description isn't great. Sometimes, it gets so rough, it shakes the whole truck pretty bad. It hasn't died and it starts good. I tried some seafoam, it didn't seem to do anything. You can tell from the pics, it looks like it's been taken care of, at least cleaned. I believe the coil pack, sparks and cables are new. Knowing that you all know just about as much as I do about the truck, where should I start with troubleshooting. I am a beginner when it comes to vehicle maintenance. But I am learning more everyday

Thanks in advance!!

https://lh4.googleusercontent.com/-Ak9MJqfMovw/UuQgtiqXFmI/AAAAAAAAUgc/bRFaHXEvQmU/w1598-h899-no/20140125_153757.jpg

https://lh3.googleusercontent.com/-agLzbWiOpyk/UuQgsS35I3I/AAAAAAAAUgQ/A9WL51nsHFc/w1598-h899-no/20140125_153742.jpg

https://lh6.googleusercontent.com/-tKlvynQpcEg/UuQgqFZfMWI/AAAAAAAAUgE/dm3Oz3wk7Kw/w1598-h899-no/20140125_153733.jpg

RonD · Jan 25, 2014

Common issue for those symptoms is a dirty MAF sensor.

read here:
http://therangerstation.com/tech_library/CleanMAF.html

SenorNoob · Jan 25, 2014

For my own purposes, I have a question. Did it start right after you filled the tank ALL the way up? IE let the pump shut off for full.

tmcalavy · Jan 26, 2014

Pull the codes. Could be shitty gas if it started doing this right after you filled the tank...water in gas is a sucky, shitty business.

DroidTN · Jan 26, 2014

RonD said:
Common issue for those symptoms is a dirty MAF sensor.

read here:
http://therangerstation.com/tech_library/CleanMAF.html

Thanks for that info. I went through the cleaning guide as described. Easy enough. Cleaning the MAF sensor didn't seem to do anything. I also checked voltage between A and B, also C and D as described in the guide. My readings were off what the guide suggests to be normal at 14.7v for A and B, and 6v for C and D. Does that tell you anything?

The engine does run more rough without the MAF powered up, but still when driving with the MAF powered, I can hold the gas at say 2000 RPM's and the engine hesitates and kinda sperodically skips.

DroidTN · Jan 26, 2014

SenorNoob said:
For my own purposes, I have a question. Did it start right after you filled the tank ALL the way up? IE let the pump shut off for full.

After I saw your post, I actually went and filled the tank up. It didn't seem to change anything about the way it ran. Just a deduction from my checking account.

1994Ranger$$$pit · Jan 26, 2014

Wonder if the catalytic converter is plugged up.
Could be as simple as a vacuum line.

RonD · Jan 26, 2014

DroidTN said:
Thanks for that info. I went through the cleaning guide as described. Easy enough. Cleaning the MAF sensor didn't seem to do anything. I also checked voltage between A and B, also C and D as described in the guide. My readings were off what the guide suggests to be normal at 14.7v for A and B, and 6v for C and D. Does that tell you anything?

The engine does run more rough without the MAF powered up, but still when driving with the MAF powered, I can hold the gas at say 2000 RPM's and the engine hesitates and kinda sperodically skips.

With engine running just after start up the alternator output is about 14.7volts, so that would be normal, after a few minutes that should drop to 13.7v, A and B is measuring vehicle voltage.

6volts reads as bad for C and D I would retest
" measure the voltage between MAF sensor connector terminals C and D. If the reading is approximately 0.34-1.96 volts, the sensor is functioning properly."

Since you have an OHM meter you can also test the Coil Pack, you don't need to remove it.
Google: test ford coil pack the easy way

Good video to watch
It can't tell if coil is 100% good, but test can tell you if one of the 3 coils in the pack is bad

Oh and your pictures of the engine look exactly like my factory '94 Ranger 4.0l, so no difference I can see

Also just as a heads up, in the '94 the heater core is the by-pass for the cooling system, there must be coolant flowing thru the heater core when engine is running, so the cold/hot setting is just a door/vent not a valve on the heater hose, like most vehicles.
I mention this because as heater core gets clogged, they all do, your engine temp gauge may start to go up above normal then back down, not close to overheating, just up above 1/2 then back to "normal", and it will be random.
Hopefully before you replace the fan clutch, thermostat, radiator, water pump and hoses, you will remember this.
Heater core comes out with 4 screws and costs about $25

DroidTN · Jan 26, 2014

RonD said:
With engine running just after start up the alternator output is about 14.7volts, so that would be normal, after a few minutes that should drop to 13.7v, A and B is measuring vehicle voltage.

6volts reads as bad for C and D I would retest
" measure the voltage between MAF sensor connector terminals C and D. If the reading is approximately 0.34-1.96 volts, the sensor is functioning properly."

Since you have an OHM meter you can also test the Coil Pack, you don't need to remove it.
Google: test ford coil pack the easy way

Good video to watch
It can't tell if coil is 100% good, but test can tell you if one of the 3 coils in the pack is bad

Oh and your pictures of the engine look exactly like my factory '94 Ranger 4.0l, so no difference I can see

Also just as a heads up, in the '94 the heater core is the by-pass for the cooling system, so there must be coolant flowing thru the heater core when engine is running, so the cold/hot setting is just a door/vent not a valve on the heater hose, like most vehicles.
I mention this because as heater core gets clogged, they all do, your engine temp gauge may start to go up above normal then back down, not close to overheating, just up above 1/2 then back to "normal", and it will be random.
Hopefully before you replace the fan clutch, thermostat, radiator, water pump and hoses, you will remember this.
Heater core comes out with 4 screws and costs about $25

Ok, I retested the C and D terminals, it is definitely 6v, that was after running for a few minutes. Could that cause my problem? Does that mean the MAF sensor is bad or just the power supplying it and what is the fix for that?

I also did a quick clean on the outside of the throttle body. It seemed to help a bit, but not much.

And if my engine looks like yours, that is a factory engine. I guess that means the explorer writing on one of those pics, must be wrong or just for that part of the engine.

So...what should I check next. Tomorrow my plan is spark plugs and I'll do the coil test, but all that stuff has been recently replaced, it looks almost new. Keep those suggestions coming..

RonD · Jan 26, 2014

It could be a '95 4.0l but everything is the same so when getting parts I wouldn't worry about the difference.

Another way to test MAF
I assume you are using a pin(sewing) to pierce the MAF wires for testing?

Remove the two bolts(8mm I think) that hold the throttle cable cover on the engine and remove the cover, this is so you can REV the engine during test.
Pierce the D wire with a pin
Set Volt meter to DC volts
Ground volt meter's black probe
Start engine
Put meter's Red probe on D wire
You should see a voltage, it may jump around a little that's OK
Now the test
increase RPMs slowly, voltage should start to go up.
Raise it to about 2,000rpms(don't need to be precise) but hold it at a higher rpm, voltage should not be spiking or dropping alot.
Increase and decrease RPMs a few times making sure voltage goes up smoothly with RPMs and then down smoothly, any wild jumping around would mean get a new(or used) MAF sensor.

If it looks like a bad MAF then recheck your meter connections, loose ground can make meter erratic

DroidTN · Jan 27, 2014

RonD said:
It could be a '95 4.0l but everything is the same so when getting parts I wouldn't worry about the difference.

Another way to test MAF
I assume you are using a pin(sewing) to pierce the MAF wires for testing?

Remove the two bolts(8mm I think) that hold the throttle cable cover on the engine and remove the cover, this is so you can REV the engine during test.
Pierce the D wire with a pin
Set Volt meter to DC volts
Ground volt meter's black probe
Start engine
Put meter's Red probe on D wire
You should see a voltage, it may jump around a little that's OK
Now the test
increase RPMs slowly, voltage should start to go up.
Raise it to about 2,000rpms(don't need to be precise) but hold it at a higher rpm, voltage should not be spiking or dropping alot.
Increase and decrease RPMs a few times making sure voltage goes up smoothly with RPMs and then down smoothly, any wild jumping around would mean get a new(or used) MAF sensor.

If it looks like a bad MAF then recheck your meter connections, loose ground can make meter erratic

No I didn't pierce the wire. My leads on my meter are sharp enough to stick them in the terminals to get a reading. I will try the method you suggest also. I watched some video that said if you unplug your MAF and it runs better, then you know its a bad MAF. Is that true? In my case, that didn't work. I was just curious.

I did start pulling spark plugs and the first one was completely coated in soot. Does that mean its running too rich or lean? And should I go ahead and replace the plugs that are black. Please excuse my ignorant questions.

Thanks!!

RonD · Jan 27, 2014

Yes, black soot on plugs means rich mix.
Just clean plugs with wire brush.

Unplugging MAF puts computer into an Open Loop that will use pre-set fuel/air mix based on RPM.
So yes it could mean MAF is bad if idle was better, could also mean wires were bad or computers MAF reading circuit is bad.

Ignorance isn't a bad word, it just means a lack of SPECIFIC knowledge that might be needed at a certain time.
So everyone on the planet is ignorant about something, period, unarguable point

Stupid on the other hand means you have the knowledge but just can't/didn't apply it correctly, and pretty much everyone on the planet has had those moments, lol.

DroidTN · Jan 28, 2014

Ok, I pulled all the plugs and cleaned them. I haven't pulled many plugs in my day, but these were nasty, caked with black soot. I put them back in and ...still the same. At this point, with the weird MAF voltage issue, should I continue down that path or maybe look at fuel injection, good spark/coil pack? I am going to get at least an autozone diag, so I can get some codes maybe. (EDIT: Their type of diag won't work cause the check engine light isn't on.)

To recap:

Starts fine, runs ok. At idle, runs a little rough, when driving, high and low speeds mostly when accelerating, there is a hesitation.

- tried fuel injector cleaner
- tried cleaning MAF sensor
- tested MAF power, seem to getting high voltage on C and D terminals, near 6v
- cleaned outside of throttle body
- pulled plugs and cleaned them, they were totally soot covered

Nothing seemed to help so far.

Thanks in advance everyone!! You guys are awesome!

DroidTN · Jan 29, 2014

Changed the fuel filter today, it seemed to help overall performance, but the hesitation is still there. Any other ideas?

94 Ranger hesistation/misfiring help?!

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