94 Ranger 4.0 XLT 4x4 5 speed seems very weak and stumbles/stutters and surges through lower gears. Once I get the truck up to speed it runs fine. Next time I stop it may do the same or may not. Very intermittent problem. Truck idles fine. I have replaced fuel pump and filter. New wires and plugs. Recently cleaned maf seems to have helped some but didn't cure the problem. Anyone have any ideas? Thanks.

 

To save a bit of money you may want to invest in an OBD I code reader, $25, '94 and earlier cars/trucks are OBD I, some '95s and all '96 and up are OBD II.
Most auto parts stores will read OBD II codes for free, OBD I readers are getting scarce, and they are cheap to buy now in any case.

Amazon has this one:

Check local auto parts stores for their prices.

OBD I codes are not very specific(neither are OBD II, lol) but can lead you in the right direction.

Not sure your engine has an EGR valve, but if it is not closing all the way you will get what you describe.

Also, after engine is warmed up and idling, unplug the IAC Valve(idle air control), engine idle should drop to about 500rpms, or engine may even stall, either is OK, but if idle stays at 750 or higher then you have a vacuum leak, which would also fit your symptoms.
PCV valve hose is a good place to start when looking for vacuum leak.

 

Thanks for your input. I'll give your suggestions a try.

 

What plugs did you put in it?

 

I used NGK but this is a new problem which wasn't happening prior to or after the plug change.
The truck is running better but still has a stall/miss while moving up through gears. Especially in 1st,2nd,3rd gear.

 

Truck doesn't have an EGR. Unplugged the IAC and trucked stalled out. I checked OBD and the main thing it's throwing now (After clearing) is oxygen sensor codes. Considering the fact that I knocked the Cats out I would imagine this is normal?

 

I would still suggest putting motorcraft plugs in it. I chased a misfire for a year. After replacing countless parts, it just turned out to be some junk autolite plugs that i put in it.

 

Actual code numbers would be helpful

No, your '94 is OBD I so there are no O2 sensors to test Cat Converters, those were added with OBD II systems, starting in '95/'96

O2 codes can mean O2 sensors are working great and reporting a problem or O2 sensors are having a problem.
This is the main issue people have with codes, they assume computer is "smart", it isn't, all it has is a "range meter" for all the sensors, if a sensor is out of this "range" then computer sets that code for you to check.

A sensor could be out of "range" because it is bad, or because it's voltage is bad, or because the system it is "reading" is bad.

Example would be if Computer set a lean code.
That could mean vacuum leak, exhaust leak, low fuel pressure, bad O2 sensor, bad wire, bad computer, lol.

 

Thanks for your reply.
I'll try to get you the codes. This is my son's truck so I don't drive it that much. This weekend I put a couple hundred miles on it.
The mis/stutter is still there. The truck acts as if it has no power as you come up through gears. So when you drop the peddle to the floor you feel stutter stutter then the power kicks in and she moves on out.
I hate to know what his mileage is as he says he has to hammer it up through the gears all the time.
I'll try to run the codes again this week and post them.

 

Ok big boy. I had this same problem. Intermittent start as well as the stutter. On a whim, I checked the fuel pump relay (18 $) changed it to a new one and away we go. Good luck