I've got a 94 4.0 Ohv, recently I did a motor swap and ever since I've been having driveability issues. My truck has good power all throughout lower speeds, but when I get on the freeway and try and maintain 60 mph or 65 it feels gutless. If I stab the accelerator all the way down, the truck hesitates for a second and then takes off but if I try and get it to pickup speed at half throttle there is no power and it begins to backfire until I get off the gas and stab it again. I've replaced fuel filter, coil pack, spark plugs, wires, tps, iacv, fuel injectors, fuel pressure regulator and an air sensor on the plenum.
I have cleaned all sensors, all grounds, maf.
Any advice or info helps.

 

Stretched out throttle cable? This comes up. Yours is 28 years old.

A vacuum gauge and a compression check can give insights to general engine health.

Did all your air intake tubing get reassembled correctly such that incoming air is metered accurately (no leaks)?

 

That could be, it may have been stretched when I tucked it out of the way for install. I'll throw a zip tie on the end and see if it makes a difference

 

+1 , I would check engine vacuum at idle, 18-21" means engine has good compression, lower can mean tired engine with low compression, compression = power

The engine computer uses O2 sensors after 3 or 4 minutes of warm up, so does the engine run better when cold, the first few minutes?
Computer ignores O2 sensors at idle and at WOT(wide open throttle)
So after warm up if engine is sluggish but has good power at WOT then O2s may be warn out

O2s are the only sensor that CAN wear out, 100k miles or 12 years, and they need to be changed, they run out of chemicals to detect oxygen in the exhaust, this also causes lower MPG so new O2s pay for themselves a few times over in fuel savings over the next 100k miles or 12 years

Clean the MAF sensor, do this every year on a 4.0l, easy thing to do
MAF sensor detects engine "load" and if dirty will cause bogging and stumbling, its also ignored at WOT

 

I will look into the o2 sensors. My maf is clean and the filament on it is intact. I pulled the maf while running and there was significant change in the way the motor ran which means it's working. The o2 sensor I pulled out of my last motor to reuse because I assumed that it was still good, my last motor didn't have this problem before she went. It runs drastically worse when it warms up and it keeps throwing codes that won't pop up when I do the engine off ignition on diagnostic. I keep.getfing 341 which is octane jumper installed. I also got back a 512 today. But it doesn't stutter or hesitate at WOT.

 

Replace the O2 sensors if over 12years old regardless

Computer is in Open Loop until engine warms up, which means it its running fuel trims from a table in memory, no calculations
After warm up computer is in Full Use, Closed Loop, and uses all its software and all sensors to calculate fuel trims in real time

Pull out computer and have a look at the 3 blue capacitors, I had to replace my 1994 4.0l Caps last year because of running issues and odd codes, those are not odd codes though, they are fairly normal, 512 will come up after battery is disconnect for any length of time, 341 just confirms jumper is in place which it should be

My computer with new Caps is as good as new now, $5 fix
Plan on replacing them regardless because they WILL leak after 20+ years of service, so just a matter of a few month or maybe years before one fails, or its already happened

 

Would you possibly have a right up for placing the caps

 

Are the caps something that could go essentially overnight? These problems have been unique to this motor.

 

The CAPs are easily seen, picture here: Ford EEC-IV

3 blue cylinders, replace with Black models, they last longer, of same uF value, and same voltage or high voltage is fine but not lower voltage

You need soldering iron and solder "sucker", wick doesn't work that well

1986 to 1994 Ford computers have this issue with the caps, they just don't last past 20 years or so
Engine doesn't matter, 4cyl to V8 used same basic computers just different software

Here is an A9L capacitor repair with pictures: Capacitor Repair: Ford A9L ECM « Moates Support
A9L was a popular V8 computer
Ever year computer was slightly different, but easy to spot the Caps

 

Do you have any ideas of what it could be before pcm? I'm not the greatest at diagnostics, but I can definitely turn a wrench.

 

Also, I forgot to mention that today it threw a 513 code. After the code popped up it cleared itself and gave 111 which is system good

 

513 Replace processor (PCM) (internal failure)

I think I would look at the PCM see if the circuit board looks OK and replace CAPs then put it back in

You can change the plugs and wires, coil pack, injectors, MAF sensor, IAT sensor, ECT sensor, TPS sensor, O2s, check the air in the tires, even empty the ashtray, but I would check the computer(PCM) first

 

Right on man. Thank you for your advice, I will get back to you with an update asap