Car guys, i need help.

[scorpion ax-10]

So after hours of internet searching and miscellaneous other research, i have got nothing.

I drive a 1994 Ranger EXT cab, splash, 4.0L V6, 5-speed Manual, 4wd. and im having a rough idle (possibly a misfire) and after a LONG period of running at highway speeds (roughly 2000 RPM) the Check engine light will come on, but after i run it at anything under 60mph for a while (about 1500 RPM) the light will shut off. i do feel low end is lacking a bit of power but that could just be me getting speed greedy, and it seems to have plenty of power and run smoothly upwards of 1500+ RPM, so thats why im a little confused, maybe the rpm is just high enough that i dont notice the stumble.... ive been told multiple things; fuel filter, ignition pack (no cap and rotor here), did plugs/wires (could possibly be wires those were new/used) told it may be O2 sensor, etc... any ideas?

Help is MUCH appreciated it does still run but id like to fix this issue

-David

[hvydty1]

I would check to see if it has a low speed idle selonoid, or high idle selonoid, or mass air flow sensor. Check to see if it has a cam or crank sensor too. Ford put sensors on sensors so tracking rough idles can be a PIA. And check for Vaccum leaks! Even a tiny leak can throw everything out of whack! Check every vaccum hose and replace any suspect hoses. I chased one on an Explorer for about 6 months before I found the dang thing.
A good way to check for bad plug wires or coil packs is pop the hood in the dark with the engine running and look for archs around the packs or along the wires. Just crazy why they put so much junk under a hood for.

[Scocrawler]

I would clean the Mass Air Flow Sensor. Unplug it, remove it from the air inlet tubing. Look for some small coiled wires in the section that protrudes into the tube. Spray them with either some special MAF sensor cleaner or some brake clean. Then blow it off with some keyboard cleaner in an aerosol can. Common issue....... Good Luck

[JasonInAugusta]

I bought AutoEnginuity ages ago for the F250.

It has since paid for itself multiple times over.

Riffraff Diesel: AutoEnginuity Total Ford Enhanced Bundle

*EDIT* Crap. I see your's is a '94 and AE works on '96-up.

Disregard.

[Die-Laughing]

You already listed most of the ideas I would have come up with but, what's the story with the ignition wires? Did it happen before you changed the wires? Are the wires you put on new or used? Well, either way.. If they are new, I would eliminate them and if they are used, The chances that its reacting the same way is possible but, not likely so, I would eliminate the wires. The plugs are new, I assume. Gapped correctly? Everything you did, I would imagine you did it all after you were experiencing the problem?

How long has it been since you did the fuel filter? I would do it if its been 1yr+.. Especially if its been several years.. That's where I'd start.

Also, check for vacuum leaks.. Look for old dry rotted vacuum lines.

[redrokin00XJ]

May need to just re-flash your computer

[hellbounder]

I drive a 1994 Ranger EXT cab, splash.



There's your problem .

[THX_138]

Plug in an OBD tester and read your code/codes while the light is on.
They should lead you in the right direction pretty quick.

From the sounds of what you are saying though, it sounds like your catalytic convertor is getting clogged/melted reducing flow at idle & low rpm's.

The "in" thing that I seem to see with local vehicles around here I fix is Expanding Foam in the exhaust. Used to be sugar or water in the gas tank.... Now I guess it's drill a small hole in the rear area of the exhaust tail pipe and blast some expanding foam in there.... ultimately reducing flow and causing all sorts of grief to O2 sensors and OBD systems

You didn't mention your miles on the clock ... If you are up past 150K you may also be looking at a lazy fuel pump. A dirty MAF (Mass Air Flow sensor), or possibly even a clogged/carbon filled EGR valve.


Your OBD check should tell you what you need. OBD went until 1996, but some vehicles started with the OBDII system in 94... I don't think Ford was doing it, but there is always a chance.

[BL-4x4]

I used to have a 1994 explorer , had similar issue, changed spark wires and plugs , got better but didn't solved , than I've started checking for small holes , and leaks on air intake , any tiny hole after the MAF sensor gives this issue , found that my air filter box was cracked and that admission tube that passes above the radiator was perfurated .. changed for a 3" bend tube and K&N filter , problem solved

[microgoat]

A plugged cat would show up more at high speed than low. Or more correctly, high load.

The 4.0 has a timing-chain issue (not sure of the exact nature of it, I have a 3.0). If the chain is stretched, it could put the cam sensor outside of where it's expected to be, which could cause the CEL to come on. And bad cam timing would also cause a lopey idle.

[Hoosierdady]

Just take it to a dealership to get it diagnosed, then replace the part at home. It'll be alot cheeper than just throwing parts at it and hoping that it gets fixed.

[Draggermirage]

I'll say the same as a few others have.

Get the codes read. You will not be able to use any of the available-at-any-auto-parts code reader though. You will need to find a shop with a Ford specific OBD I scanner if not a dealer. I'm sure there is a way to pull codes using a buzzer, voltmeter or a bulb. A quick google search will yield results.

From there, post up what codes get pulled (or even google them) and that will get you closer towards what you need to do.

Marcus

[gbaileyo7]

Isn't the timing chain issue specific to the 97+ sohc 4.0?

Does the problem exist when the engine is cold? The computer does not read the o2 sensors until the engine reaches a certain temp so if it does not act up when the engine is cold then I would lean toward the o2 sensors.

[offroadace]

Usual standard is if the light is On and steady it is something with the emissions (intake, sensor, plugs, wires, gas-cap - something like that) if it is blinking then it is something more serious and needs to be investigated based on codes.

Start with a new gas-cap.

[Draggermirage]

Originally Posted by offroadace

Start with a new gas-cap.

It's wasted money until codes are pulled...

On top of that. Pre OBDII cars did not do checks on emissions related stuff (Purge valves, gas caps, evap system, etc.). OBDI systems only tripped codes for fuel trims, any obvious sensor circuit malfunctions, ignition misfires (although sometimes rare) along with obvious dead sensors.

The truck is smart, but not that smart.

Marcus

[scorpion ax-10]

OK to clear air im at almost 174000 miles i will try to clean the MAF now, and maybe gut the cats later this summer (but soon-ish) i was kind of thinking it may be a fuel system thing, but not sure, i bought the truck used last january and really like it, ive done a lot of work but i feel that is just typical used vehicle stuff, i cannot pull the codes as the light shuts off shortly after i get off the highway and only comes on after hundreds of miles on the highsay constantly ( i live 300 miles from where i go to college) and that is when i first noticed that... im leaning more towards emissions as its a common issue at idle but sparratic on the highway (light didnt come on at all when i made the trips in the winter, but did in the summer) thanks all for the suggestions, i will definatly implement those


EDIT; cleaned the MAF and the IAC, no noticeable change.....

[Duuuuuuuude]

ctrl+alt+delete, reboot in safe mode.

[BL-4x4]

Originally Posted by scorpion ax-10

OK to clear air im at almost 174000 miles i will try to clean the MAF now, and maybe gut the cats later this summer (but soon-ish) i was kind of thinking it may be a fuel system thing, but not sure, i bought the truck used last january and really like it, ive done a lot of work but i feel that is just typical used vehicle stuff, i cannot pull the codes as the light shuts off shortly after i get off the highway and only comes on after hundreds of miles on the highsay constantly ( i live 300 miles from where i go to college) and that is when i first noticed that... im leaning more towards emissions as its a common issue at idle but sparratic on the highway (light didnt come on at all when i made the trips in the winter, but did in the summer) thanks all for the suggestions, i will definatly implement those


EDIT; cleaned the MAF and the IAC, no noticeable change.....

have you checked the admission for small holes or cracks that can leave air go in without passing the MAF sensor ??

[RickGrimes]

I used to have a ranger and those IAC's are known to go bad....on another note my mom had a Camaro with those symptoms and it ended up being the intake manifold gasket.

[losiking1]

Also check fuel lines and tank for leaks. Give them a good going over as even a small almost unnoticeable leak can cause grief. Canadian weather wreaks havoc!! I always said vehicles should be tested in our climate especially out here on the east coast.