completely guttless AND terrible mpg

so its a 1990 ranger 2.9 obviously lol

it has no power, like cant carry its self up a hill in fourth gear at 55. I do have slightly oversized tires, but its done this since I got it. and I had an '87 ranger 2.3 on bigger tires and it could easily pull its selp up the same hill in 5th.

the truck also gets really terrible gas mileage to compare, my 87 bronco with a built 450 horse power 390, on 38" tires and it gets 12 mpg, this ranger gets 9..

I have replaced the cap, rotor, wires, plugs, set the timing with the spout unplugged, replaced the tps, the map, the intake air charge temp sensor, I have no engine codes..

any help would be fantastic!

Buy a vacuum gauge, $20-$25, great tool for all gas engines.

Good read here on tests with vacuum gauge: http://www.gregsengine.com/using-a-vacuum-gauge.html

Couple of things come to mind, low compression or partially clogged exhaust.

If you have a code reader then I would get computer to set a code, unplug O2 sensor or MAP sensor and go for a drive, see if CEL comes on, you are just checking the sanity of the computer.

I would also pull out the spark plugs and see what they tell you about engine combustion, lean or rich, a little oil maybe.

Spark plus look rich, I already did the vacuum tests, it all comes up good acts great, I was gonna do a compression test but I hate checking all the cylinders lol. I've ran two cans of bg44k through it and it hasn't helped at all, I haven't changed the fuel filter yet, the fuel pressure running is about 40 even under load on he highway, engine off it stays at about 42... And more ideas? I would like to have it be able to move

Oh and I also replaced my coil with a cheap little msd I had laying around

Check Fuel Pressure Regulator(FPR)'s vacuum hose, if FPR diaphragm leaks, fuel is sucked into the intake causing Rich running and lower power from it.
Small leak won't effect pressure but will effect engine air/fuel mix.

Also check MAP sensor's vacuum hose, if it has small cracks MAP reads lower vacuum which means engine is under load to the computer and needs more fuel.
Also make sure MAP connector has clean terminals and is dry inside.


Vacuum test should have given you info on compression.
Crawlarado = Colorado I assume so you will have some elevation there.
MAP sensor should compensate for that.
Vacuum by elevation should be:
Sea level-1000 ft. 18-22
1000-2000 ft. 17-21
2000-3000 ft. 16-20
3000-4000 ft. 15-19
4000-5000 ft. 14-18
5000-6000 ft. 13-17

If you are on the low side of the above then your compression is low.

Also cranking vacuum, disable spark and crank engine, you should see about 5" steady, if it varies then cylinders aren't all pumping the same.

With pre-'95 computers you should reset/reboot them after making any changes or cleaning stuff up.
OBDI reader can do that or unhook battery for at least 5 minutes.

I have checked the fpr and it has no leaks, the map sensor vacuum line had no cracks, I'll check that again too see what I'm at for vacuum cause I have forgotten and I'll get back to you. The map sensor is clean and dry

I'm at 5,500 feet, at idle I'm floating between 14-15 hg.

Vacuum isn't high but mid-range for an older engine at that altitude.
N/A engines at that altitude are low on power, which is why turbos are almost mandatory on new cars/trucks sold in Denver, lol.

When you first turn on the key one of the first things the computer checks is the MAP sensor to get the outside air pressure(altitude), this is what it bases the engines vacuum against as far as engine load and air:fuel mix.
Test if MAP holds a vacuum, it should, vacuum pump is good but just sucking on it's hose and seeing if it will hold vacuum is fine as well.

Basically you have the MAP data that the computer uses to calculate 14:1 air:fuel
Then the O2 sensor data that the computer uses to test if it's original calculation is correct.
Computer continually uses less and more gas(injector dwell time) to keep O2 sensor in the "sweet spot", not too much oxygen in the exhaust(lean) and not too little oxygen in the exhaust(rich).

The system is self checking in that the computer has in memory the expected fuel use(dwell time) of a 2.9l engine at X,XXX RPM(speed density system)

And with the MAP on one end and the O2 on the other end, I would expect it to set a code if it was running too rich.
Unless O2 sensor was reading extra oxygen from exhaust leak or was just getting too old.

I'll test the map to verify later today,

I have a exhuast leak after the cat but the lack of power ha been longer than the exhuast leak.

It kind of acts like it has a plugged up cat but all of the tests I've done say otherwise.

I'll check the eec again for codes as something may have changed

Map sensor holds vacuum fine, no check Engine light

One thing I noticed was that when I changed the tps it kept revving up when I was stopped (it's a 5 speed) so I replaced it again, same thing. Then I put the original one back on it and it stopped doing it.

It hesitates from stop and after shifts for around 500 rpm

TPS wouldn't explain rich plugs or poor MPG

TPS is similar to the accelerator pump on carb in a way.
Speed Density Fuel injection computers rely on intake vacuum level(MAP sensor) and RPM(TFI module) to calculate fuel required for the 2.9 liters of air the engine uses every 2 RPMs.
With a carb you would push down on the gas pedal and accelerator pump would squirt in some extra fuel into the air stream so you would get fairly instant acceleration.

With fuel injection there would be a slight delay before MAP sensor reads vacuum drop from gas pedal being push down, so TPS was added to give the computer a "heads up" to add more fuel right away.

So your hesitation could be related to TPS, good news is these are very easy to test.
TPS is a variable resistor like a light dimmer or volume control
TPS has 3 wires.
Top - 5volts
center - variable voltage
lower - Ground

Use a volt meter set for DC Volts, get a sewing pin, straight pin, to pierce wires
Turn key on, engine off
Top wire is 5 volts from the computer, put pin in wire and test it, 4.8v to 5volt
Center wire , is the voltage sent back to the computer, test it
With throttle closed it should be .69-.99volts, below 1volt
With throttle wide open it should read above 4.5volts
You need to slowly open throttle while watching this voltage, it should steadily increase, no jumping or dropping, same when closing throttle, it should steadily drop.
If you see any jumping replace TPS.
TPS is also a "learned device", it you swap it out you should reboot/reset computer, use an OBD reader or unhook battery for at least 5 minutes to reset

Computer is on the other end of TPS and it could be the problem as well, and with the other issue of running rich without a CEL it could be THE problem

Computer reads oxygen level in exhaust using O2 sensor, too much oxygen means lean, too little oxygen means rich.
Computer adjusts the fuel injector's dwell time(the time they are open) according to oxygen level in the exhaust.
If O2 sensor is bad engine could run rich without computer knowing it, but computer checks O2 sensor a few times a second, computer changes dwell time often and watches O2 response, if it is slow or not responding computer will turn on CEL and set a code.
The exhaust is the exhaust, MAP sensor or TPS don't matter in what the O2 sensor reads as the oxygen level in the exhaust.
A leak in exhaust manifold or a misfiring cylinder adds extra oxygen to the exhaust, I had an O2 sensor that unscrewed itself 1/2 way and was sucking in air so my 4.0l started running rich, but no other issues.

Interesting, so if I unplug my oxygen sensor, I should get a cel right? And it should revert to fuel tables? So it should run better if its the issue? I'll hit hhe junkyard tomorrow and pull a few computers and see if they make a difference.

If the oxygen sensor doesn't throw a code when unplugged does that mean faulty Ecu? And I should swap it? Or maybe just bad bulb, but I think it's on with the key on engine off..

Yes, if you unplug any sensor or control wires computer should turn on the CEL.
O2 sensor is not used for a few minutes on cold start, it must be heated to above 600degF before it will give accurate oxygen levels, but no connection should still turn on the CEL.

And yes, unplugging MAF or O2 sensor should cause computer to go into Open Loop, it uses Open loop when engine is cold, or if a main sensor is off-line or it's data/info isn't within "normal" parameters.
In Open Loop computer uses a Table in memory for air:fuel based on engine size and also Long Term Fuel Trim data for age of engine and parts

Okay I'll unplug it, but if that does make it run better all that means is I have something that meters something is off and their isn't really a way to find it, right? Not easily I mean