Sorry for the dramatic title but here's what i got.
2000 Ford Ranger XLT 4X4, 3.0 Flex, 176K.

Driving fine, no problems then decides to just stop doing that and run like crap, heavy shaking and stuttering when driving. CEL pops on for misfire on the #6 cylinder. Ok cool, changed the all spark plugs and wires (you'll find out i didnt test much and just started changing things b/c well, im dumb and its an old truck i havent owned long). Still runs like crap, ok cool. Changed the coil pack, nothing. Changed the #6 injector. Still crap. Do a compression test, good results. Fuel pressure, again good. Ok so i dig a little deeper, and i see im still having misfires just not frequent enough to throw a CEL. So i decide to check out the Fuel filter....it had a date stamp of 2004!! on it. New fuel filter, still issues. Check for vacuum leaks, all good( except the A/C, which issue for another day) So now im going to change all the injectors. Had brand new 24lb ford mustang injectors in the garage so i figured hell why not? 3lbs difference shouldnt make that big of a difference right? (Again, im dumb) Truck runs fine, other than hunting idle. Test drive it, runs great for 2ish miles and then goes in to limp mode for 02 sensors reading too rich. Truck does its best diesel impression belching black exhaust and i baby it back to the garage. Order the right injectors, change them out. Truck sounds and Idles great!! Then comes the test drive.......all acceleration is gone. Throttle shows wide open but the revs and acceleration dont when pedal is to the floor. It struggles to get to 50, stays there and after awhile will "break open" and accelerate normally until you slow down to a stop and then it does it all over again. Had it accelerate twice from stop normally but thats it.

My question....WTF??

 

Welcome to the forum

I think you are approaching an engine problem with the wrong info

Spark
Fuel
Compression
A cylinder fires with all 3, or misfires if 1 or more are missing

No matter how much electronics is added it just comes down to those 3 things
And electronics RARELY have a problem, not never, but rarely, just FYI......90% of all electronic sensors or controls changed by DIYer were working fine

Compression test "was fine"??????
Numbers please, 3.0l should be high 160's

Spark plugs were good to change they do wear out, but that wouldn't be an abrupt change, you would notice rougher idle that got worse over time.
A vacuum leak can happen suddenly, which causes misfires, easy to test for vacuum leak
Exhaust can get a blockage which happens suddenly, which cause misfires and poor higher RPM power

There are only 3 coils in the coil pack so if one fails then 2 cylinders stop working at 100%, so not a bad change, just not a common failure

You do need to swap back in the stock size injectors to move forward.

You should Clean MAF sensor every 2 years, and IAC Valve as well.

After engine is warmed up, and idling, unplug the 2 wires on the IAC Valve, idle should drop down to 500rpm or engine may even stall, if not then you HAVE a vacuum leak, if RPMs drop then you don't

You can use a vacuum gauge to test many many things on any gasoline engine, $20, good read here: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine
Exhaust blockage can be tested

Bluetooth OBD reader............$15-$40, if you have a smartphone and will be driving vehicles made after 1995 then you NEED one of these, works on ANY BRAND of vehicle sold in the US or Canada from 1995 and up, required by LAW, so long term use for current and future vehicles
You can read codes of course, but you can also see LIVE DATA while engine is running or while driving(hands free display!!!)

 

Thanks for all the info.

Im aware of the main causes of a misfire and am also aware people tend to overthink them haha.

Correct Injectors have been installed, MAF has been cleaned and battery disconnected to reset everything. Used the old fashion way of looking for vacuum leaks by spraying starting fluid on hoses.

Numbers during the compression test were "fine", lowest cylinder being mid 160's and highest being low 170's. ( Should say though, thay even if they were slightly lower it wouldnt necessarily mean it was an issue as long as they were all in proper range of one another). Fuel pressure was 50ish Psi.

I do own a Bluetooth OBD2 scanner and use Torque Pro frequently ( i hate dummy gauges. ) Though I'll admit im still learning my way through all the different readings.

The misfire is completely gone since i replaced the injectors. This latest issue with the acceleration is a completely new symptom and is why im so frustrated. I never post here because most things have been covered over and over but i feel as though i went through the proper ways of attacking this but am now more lost than i was when i started.

 

Thanks for the info. I am, however, aware of what causes a misfire. Spark, fuel, air. I have all 3.

Compression was fine, lowest reading being mid 160's and high was low 170's( although i may argue that it could be lower and still be fine as long as all the cylinders are withing proper range of each other) Fuel pressure was 50ish psi. I used the old method of starter fluid on the vacuum lines as well as a visual inspection and found nothing.

Ordered and replaced the injectors with OEM Denso's. Cleaned the MAF and pulled the battery terminals to reset. Havent checked the IAC Valve will make sure to do that.

Definitely agree about the OBD2 Bluetooth Adapter, i have one and use it and Torque Pro very frequently ( I hate dummy gauges) Although I'll admit im still pretty green on the full functions of it and the different readings.

Its important to note here, that the misfire issue is gone. No codes, no cylinders showing any misfires at all. This is a completely new issue (in that it was not happening before or during the misfire) that has come up involving acceleration issues.

 

Then look at the other end of the "air pump"(engine), old air(exhaust) has to get out to let new air(and fuel) in, so partial exhaust flow blockage will cause limited power, as RPMs increase pressure backs up in the system

Vacuum gauge will tell that tale, good read here on testing for that and other engine issues: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

 

So i took off the IAC and sprayed it down with carb cleaner and the connector with electrical spray. I ended up getting a p1504 pending code for my trouble haha.

Anyways started the truck up and pulled the IAC connector off and the RPM's dropped so thats a small good sign anyways.

I am obviously still running rich however even after swapping to OE injectors, i can smell the fuel and have black smoke from the tailpipe when revving the engine in the higher RPM range.

One or two strange things ive noticed are the values im getting for both my fuel trims and o2 voltage. Screenshot is at idle.....any idea whats going on?

 

yes, no vacuum leaks if idle dropped when engine was WARMED UP

Have you programmed the Torque app for your model vehicle?
Not sure it needs it but it might

OBD2 uses many PIDs(packet IDs)
A code reader sends a request for a specific PID to the computer, computer sends back that data

Your engine has 2 or 3 narrow band O2 sensors
Bank 1 sensor 1(passenger side near engine)
Bank 2 sensor 1(drivers side near engine)
Bank 1 sensor 2(passenger side after Cat converters)

If you have factory Dual Exhaust then there would also be Bank 2 sensor 2(drivers side after Cats), so 4 total with dual exhaust

Each one has a specific PID the OBD reader must request
They should be in the order listed above, as sensors 1 2 3 and dual exhaust 4
But if you program reader for Ford V6 you should get them as listed above, instead of 1 2 3 and 4, and no sensor8, lol
Torque app can also show O2 as O2 1x1, bank 1 sensor 1, so O2 1x2 would be bank 1 sensor 2(after CAT), 2x1 bank 2 sensor 1

Sensor 2's should always run about .7-.8 volts and be fairly stable, these are there to make sure Cats are working
Sensor 1's are what the computer used to set on the fly air:fuel mix, and these start the ball rolling on the lean or rich codes, but don't set them

Lean and Rich codes are set by Fuel Injector Open time
Computer uses RPMs, throttle position and MAF data to calculate the weight of the incoming air, it then calculates the open time for each injector to add enough weight in fuel to that weight of air to get the 14.7:1 ratio needed.
After air:fuel mix is burned, O2 voltage shows the amount of Oxygen in the exhaust
.9volt is very little oxygen, so Rich
.1volt is alot of oxygen so Lean

Computer then adjusts injectors open time, reducing open time if O2 shows above .6, and extends open time if O2 shows below .3
This is called Fuel Trim
If for example the calculated open time was 100ms, milliseconds, and that represents Fuel Trim 0
If O2 showed .9 the computer would change to 98ms, which would be -2 STFT(short term fuel trim)
If O2 showed .1 then computer would change to 102ms, which would be +2 STFT

If computer needs to change open time + or - 15 then it will set a Lean or Rich code, the engine was never running Lean or Rich, because all this happens in seconds, the Code means computers base calculations are off with data available.
Computer can detect a dirty MAF/air cleaner or Vacuum leaks or Low fuel pressure or plugged fuel filter, or plugged exhaust, or any number of mechanical issues, it can only base its calculations on what it "sees" which ain't much, lol.

The black smoke is more than likely a leaking injector, or shorted injector wire, check each spark plug for signs of Rich Burn, then check that injectors wires
All injectors get 12v key on, computer Grounds each injector to open it, so a short to ground on that wire open injector

 

Havent had much time to mess around with the truck lately, but I believe i may have found the issue. In the picture, the lower number beside the word "Max" (589.3) is the temperature of the exhaust ENTERING the Catalytic converter and the top number (443.5) is EXITING it. So between the issues im having now ( No acceleration, sporadic RPM, rich smell, black smoke from exhaust) and the known issues i either had or created (misfires, wrong injectors)seems to me I killed my Cat and thats my issue.

 

Rich running will "kill the Cat" over a long period, it over heats a burns out

The computer constantly shifts to Rich and back to keep the Cat hot, unburned fuel is what heats up the Cat and makes it work

Not sure where that temp came from?
Temp gun? if so where on the Cat was it pointed, that reading is not that unusual, 400-600deg is when Cat starts to work

 

Yea its a a temp gun, the temperature itself is not unusual, however with the front of the Cat being well over 100° hotter than the exit its usually a pretty big red flag that the Cat is done for. Typically the exit or end of the cat should be slightly hotter than the front, not the other way around and certainly not by as much as my temp gun was showing.

 

Yes, sorry I miss read your post, that shouldn't happen, rear pipe by O2 sensor should be hotter than front entry pipe

 

Gutted both cats. Truck runs fine until normal operating temperature and then continues to bog itself. No acceleration no power. Seems since it only happens at operating temperature that something screwy is happening once it goes from closed loop to open. So another day and another defeat. Going to keep wracking my brain about it but almost at the point where i need to find a trustworthy mechanic. ****.

 

You mean once it goes from OPEN Loop to CLOSED Loop, you have problems.

The "Loop" is the O2 sensors, they need to be above 600degF to read oxygen levels correctly

So on cold start the computer relies on Factory Mix tables and MAF sensor data only to set air:fuel ratios, so no Feedback, or no "loop", so an "open loop"
Once O2 sensors start to work, get hot enough, then they supply real time feedback on the oxygen levels in the exhaust so computer can switch to "on the fly" air:fuel mix calculations, so there is a complete "loop" for calculations.

 

Howdy, I'm new here but I gotta say, if this thread is typical of the exchange of knowledge and ideas, I'm gonna like it here!

 

Since my last post I'm not sure what I even did to correct anything, but at the very least for a long time it was running "ok" just rich but no power loss or black smoke. But now it's all back Haha. I still know just as little as I did then but I've read more of your posts on this site and others, and I must say you are quite possibly the most helpful mechanic on the web Haha. So I will say that when the extremely rich condition on both banks came back, I tried your method for checking for a leaky injector (flooding procedure) and got no fire. I then pulled all the plugs, which were all pretty evenly black from too much fuel. So I'm thinking it's not an injector when it seems all cylinders are having the same issue. So, to recap what's been done in a little over a year. MAF, Injectors, Plugs, Wires, Coil Pack, Fuel Filter, O2 sensors all replaced. Cat gutted, Vacuum leak smoke checked, compression within range on all cylinders, Fuel pressure within range at the rail. But still popping rich condition codes and having the dreaded black smoke no power. It's got to be a sensor somewhere or another because it runs fine when cold on factory settings. Just dont know which. Maybe some clog in fuel return line? My 00' flex does still have both lines running from the pump. I'm honestly out of ideas.

 

Unfortunately you are down to the PCM(engine computer) being the source of the problem.

The 2000 Ranger 3.0l Flex Fuel should have a Fuel Sensor near the fuel filter under the cab, this tells the computer if you are running gasoline or E85(ethanol)
With E85 the PCM must add more fuel than with gasoline, and this could be the source of the flooding
The sensor is sending the wrong fuel type, its an "on the fly" detection so wouldn't set any codes and could come and go.
Check connector and make sure 3 contacts are clean

Rangers only used these in 1999/2000, in 2001 new PCM software just used the O2 sensor feed back to determine fuel type, i.e. O2s would get Leaner and Leaner as E85 made its way thru the fuel system, so Ford allowed higher + fuel trims in the Flex Fuel software
1996 to 2000 Taurus flexfuel used same sensor
These sensors are VERY EXPENSIVE, $650-$900 new

There are flex fuel signal replicators, Google: ford flex fuel sensor replicator
These send the PCM the gasoline fuel type signal all the time, so you can't use E85 anymore, if you ever did, lol.
Much cheaper, but still expensive

And it could still be a PCM issue, mis-reading your perfectly good flex fuel sensor, I don't know

Flexfuel sensor sends out a square wave form so its not a simple voltage test to see if its working, and its why the replicator is not cheap, because there are chips inside to duplicate this wave form for gasoline fuel type

A Ford dealer may be able to test the sensor, not sure if they can or the cost to do it, but a phone call is free, lol