Several little symptoms...any idea what the problem(s) could be?

Maybe I'm just being crazy, but it seems like I have several "little" things that are off. I'm also inexperienced...so maybe not crazy, just stupid. This is on a 95, 2.3L 5-speed with 60,000 miles (it just got lucky and wasn't driven much).

1. Inconsistent RPM once warmed up @ idle: Going by my $24 Bluetooth ODB2 scanner, it's very quickly varies between about 720 and 760. I didn't notice until getting a scanner - but now that I know to look, I can also (barely) see it via the RPM needle.
   
   
2. Rough idle once warmed up...I think. Can feel it a bit in the cab, and the stick shift seems to shake an excessive amount. It's smooth at higher RPMs. Doing a test via gas + brake, the motor mounts *seem* to be OK.
   
   
3. Vacuum readings. Edit: OK, using a vacuum gauge, not the weird numbers from my ODB2 adapter: When the car is deciding to idle smooth - vacuum reading is barely flickering around 20. When car is deciding to idle more roughly - vacuum is very quickly (needle is a blur) fluctuating between 19.5 - 20.5
   
   
4. Long term fuel trim: Both banks fuel trims pretty much move together. Let the car sit and warm up - and at idle I've seen it as high as +11. Drive - it varies a lot, but tends to be +1, +3, +5, something like that. Idle *after* driving, and tends to go higher, but pretty much never above +7.
   
   
5. Temp gauge never gets above barely "warm", but going by the ODB2 scanner - the coolant temp is 179-191 while driving. So...that temp gauge should be a cosmetic issue only and disregarded, right?
   
   
6. No engine codes
   
   
7. Mileage pretty consistently 22.x mpg. Nothing feels off or weird when driving.

So...?

If it matters, the engine-related things I've done: New spark plugs, fuel filter, PCV valve, coolant (and it's not low), & fan clutch. In addition throttle cleaning, IAC cleaning, & MAF cleaning. On one side the plug wires are new, on the other they're original.

Sorry in advance for this "well it seems a little funny..." question.

1. target idle warm is 700-750 on manual trans models, could simply be partial misfires, incomplete burn causing slight up and down.

2. misfires as said above, this could be Cam Position Sensor(CPS) slight off time.
The CPS times fuel injectors, injectors opening early or late can limit fuel in the mix so lean misfire occurs, this is not a dead cylinder misfire, just less power than a full burn, which can cause the roaming RPM and vibrations at idle.
Could be dirty fuel injectors, run a can of Seafoam in the gas tank.
With that low of miles a few of the valve guide seals are probably cracked, if an engine sits for long periods these seals dry out, when engine idles vacuum is highest, this will pull a small amount of oil down the intake valve stem, when sucked into the cylinder you get a weak ignition so less power, roaming idle and vibration.
With all the above the misfires would go away as RPMs increase.
These are all just guess's

3. There is no "vacuum" sensor, so not sure what that reading is from, could be DPFE sensor(part of EGR system), or EVAP system, yes, normal gas engine vacuum would be 17-21"

4. Fuel trim at idle should be around +7 to +10 so you are right on, idle is suppose to be rich.
-5 to +5 is what it should be while driving and short term fuel tirms

5. gas engine operating temp should be 195-220degF, some one may have put the wrong thermostat in, popular wrong thermostat is a 180degF, correct one is 195degF.
Misconception about thermostat is that it controls over heating, wrong.
Thermostat maintains the LOWER operating temp range, 195degF, the 195-220degF range is where you get best MPG and cleanest oil, water and fuel contamination burns of faster above 190degF, and all oil's viscosity(weight) is rated at 212degF, normal operating temp.
Ford temp gauge usually has 220-225 as the 1/2 way point, so normal warmed up engine should be above 1/3 and below 1/2
You should be running hotter.
Could be in the 24MPG range, but in the winter months MPG goes down a bit as colder air is denser, which requires slightly more fuel, but you get more power, lol.

All in all it reads like a very good running 19 year old engine.

Two thoughts. If you do not have a MAP sensor, the vacuum may be 'computed' by the ECM from the incoming air flow and the rpm.
The valve stem seals should not be dried out as oil doesn't evaporate to any large degree, and the cam and followers are bathed in a hurricane of oil when the engine is running. If you have little faith, remove the cam cover and start the engine. You will rustproof your underhood areas and possibly make your drive slippery. I have an 85 that has the factory seals and ~74k miles with no valve stem seal problems.
You can test the seals by coasting to a stop from high speed, throttle plate closed. When you accelerate, if the seals leak, you'll get a slight puff of blue (oil) smoke from the coast-down vacuum pulling the oil past the seals.
I think I would replace the thermostat with a new Stant or Motorcraft 195F. I think I would also replace the timing belt as it is almost 20 years old. I don't know where your truck lived, but suspect that some areas may have weather and climate that cause a belt to deteriorate more than others, even with the lower mileage.
tom

Thank you both.

I bought two 12oz bottles of Techron fuel system cleaner, and may try Seafoam after running those.

I've actually been having a hard time figuring out if I have a MAP sensor or not...and if not, what that vacuum reading is coming from.

For the running temp - OK, thanks! The thermostat is a 192F. The first thing I did after noticing the low temp needle was change the thermostat, but it didn't make any change. Now I'm trying via another thread to figure out what's going on specifically with that: http://www.therangerstation.com/forums/showthread.php?p=1496896#post1496896

1995 will be a MAF(mass air flow) sensor

RonD said:

1995 will be a MAF(mass air flow) sensor

Click to expand...

I definitely have a MAF sensor. So then does the ECU calculate the "vacuum" via the MAF readings/RPM as the other poster suggested?

As said not sure what that reading represents, if it is suppose to be engine intake vacuum then it is wrong, so if it is calculated then it has a parameter that is missing or wrong.

OBD II PID(packet ID) 0B is for "Intake manifold absolute pressure", but your Ranger doesn't have a sensor for that, other engines do and OBD II is generic, so includes all parameters, even the ones not used by your engine.
Yours does have a DPFE sensor, which does measure pressure differences, so it could be that reading.
The 24.5 is in kPa(kilopascal) which is 3.5psi or 7.2" mercury, so low not high, if it is intake vacuum

I just realized I never replied to some other things:

Burning oil - unsure, but seemingly it's not losing even a tiny bit of oil. e.g. - drove 3,000 miles/6 months, and the oil dipstick mark never seemed to drop even a little.

Timing belt - I've thought about it, but I've found out this is a non-interference engine, so it's no big deal if it breaks. Maybe because of that, the service schedule doesn't include a replacement interval at all. Since I'm not all that competent, changing it myself would be really difficult...so I'm thinking I'll just leave it, and if it breaks while I own the truck, just get it replaced then.

RonD said:

5. gas engine operating temp should be 195-220degF, some one may have put the wrong thermostat in, popular wrong thermostat is a 180degF, correct one is 195degF.
Misconception about thermostat is that it controls over heating, wrong.
Thermostat maintains the LOWER operating temp range, 195degF, the 195-220degF range is where you get best MPG and cleanest oil, water and fuel contamination burns of faster above 190degF, and all oil's viscosity(weight) is rated at 212degF, normal operating temp.
Ford temp gauge usually has 220-225 as the 1/2 way point, so normal warmed up engine should be above 1/3 and below 1/2
You should be running hotter.
Could be in the 24MPG range, but in the winter months MPG goes down a bit as colder air is denser, which requires slightly more fuel, but you get more power, lol.

Click to expand...

Hey thank you for that - that got me on the path to fixing the engine temp. once you let me know it was wrong! After messing around a lot - it was just that coolant was leaking past the thermostat. It did this with a Motorad, a Napa Premium, and I imagine - with the Motocraft I had put in long ago, but hadn't helped. Short term - I put gasket sealant in there to seal it better, which got my operating temps to 185-195. Then via trial and error, have covered a certain ratio of the radiator - so I'm now getting 190-210 when driving. I prefer to be a on the low side, as I want room for freeway driving.

Long term: New thermostat housing on the way, which I hope will allow a thermostat/it's gasket to seal properly. I'll test it in the sink (seriously - that's how I finally figured out the problem with the current housing).

Update on idle

Sometimes it's smoother at idle than other times. No apparent pattern. However, I now know that when the idle is rougher - the vacuum (measured via a proper guage) is also fluctuating. When idle is roughest - the vacuum is fluctuating very quickly 19.5-20.5 (so fast the needle is a blur). When idle is smoothest - the vacuum is barely flickering around 20.

It's a 4 cylinder with a simple IAC setup, that rpm range is completely normal for idle, I wouldn't worry about most of the stuff you are asking about as they are normal... If there is a MAP value showing it probably is just an estimate

Not sure if you've seen this, but it is in the Tech Articles section...

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.shtml

If the vacuum tester is moving faster than this indicates maybe it means you have several valves that need attention.