I've been hahavi what seems to be idling issues in my 95 ranger. I installed a new timing belt a couple months ago, a crankshaft position sensor when I started having the current issues. I'd had a vacuum leak going to the switch in the cab that I found a month or so back After driving around 50 miles a day for a month or so with no issues and no check engine light I started having my current idle issues.

The current issue is intermittent and I can't seem to replicate or fix it. Sometimes it runs fine for an hour and my whole outing. Sometimes it starts right up with a rough idle, not responding to the throttle. Sometimes it will start and run great for a bit and then start the rough idle. I've cleaned the egr, checked the diaphragm with a mightyvac, checked and cleaned the maf sensor. it seems to be intake air related because the code is a lean. Some YouTube videos suggest the purge canister but I wanted to see if any opinions here led to something else.

Sorry for the long post, I wanted to include anything I felt pertinent and am able to answer further inquiries.

Thanks in advance.

 

Welcome to the forum

Cab vent controls are vacuum operated but are isolated from the engine system by the Vacuum reservoir and check valve

Easiest way to see if you have a vacuum leak is to warm up the engine, 10min.
Let it idle and unplug the IAC(idle air control) Valve's 2 wire connector.
Idle should drop to 500rpm or so, or engine may even stall, either is good, it means no vacuum leak

If idle doesn't drop then there is a leak, at that point you remove 1 vacuum hose at a time from the intake and plug its port with your finger, when Idle drops you found a leak, shut off engine and follow that hose to device it is used for.
Fix leak and repeat test

The way the air/fuel mix system works is fairly straight forward
The Computer is loaded with software and mix tables for the engines size, a 2.3 LITER engine in this case, so the computer "knows" how much air should be sucked in to this engine at any given RPM and throttle position.
But air:fuel mix is a WEIGHT RATIO, not volume, 14.7:1 is the air:gasoline ratio, 14.7 POUNDS of air to 1 POUND of gasoline, 14.7 grams of air to 1 gram of gasoline

Computer "knows" how much gasoline weighs, and its weight doesn't change much with temperature or altitude
Weight of Air on the other hand changes ALOT by temperature and altitude, i.e. "hot air rises", why?...because it is lighter than cooler air, different weight

MAF(mass air flow) sensor reports the WEIGHT of the air coming into the engine, if it gets dirty then weight will be off so air:fuel mix will be off, or if ALL the air coming into the engine doesn't pass thru the MAF sensor then total air will be off, which is why Vacuum leaks are a problem, unreported air.

After the computer calculates the WEIGHT of the air coming in, it opens fuel injectors to add the correct WEIGHT of gasoline, this is 0 Short Term Fuel Trim(STFT)
If O2 sensor reports Lean after this mix is burned, then computer changes to +2% STFT, then +4% STFT, then +6% STFT....until O2 shows balanced burn, all this happens in under 2 seconds, its very very fast
The % is an actual percentage, example: if computer calculated 100ms(milliseconds) open time for the injectors to add the correct weight of gasoline, then +2% STFT would be 102ms open time, a 2% change
-10% to +10% STFT is fairly normal as engine and systems get older, when STFT or Long term fuel trims(LTFT) get into the 15%-20% range the computer will notify driver, CEL on, that its calculations are too far off, so there is a problem.

So Lean or Rich codes are set by Fuel Trims, which are injector open time percentages
The engine is never actually running lean or rich except for the 2 seconds it takes to balance O2

Computer doesn't have a Fuel Pressure sensor, it is programmed at the factory for expected pressure at each injector, 1997 and earlier Rangers used 30psi pressure, 1998 and up 60psi
So if fuel pressure is low then you would also get Lean code, because less gasoline is flowing in when injector is open, so computer has to open injector longer, + Fuel Trim and Lean Code
In 1995 pressure would have to be below 20psi, 33% lower, to set code, it is expected that pressure will be lower over time, but 33% lower means something is wrong

The point of LTFT is to adapt computer to an aging system, i.e. lower fuel pressure, small vacuum leaks, aging sensors and wiring, LTFT allows computer to "remember" systems condition when it is restarted to drive again.
LTFT is used in computer's calculations for 0 STFT, so if LTFT is +20 and STFT is +10, then that's actually +30 STFT, and a concern. lol.

LTFT can't be Cleared, so it may remain high even after you fix a problem, watch it over a few days to see if it is coming back down after any engine work
Tthings don't have to be perfect, but they do need to be within operating range or you get notification, CEL on and codes

Upstream O2 sensors(closest to engine) last 100-125k miles then start to run out of chemicals, like Batteries do, and they will cause lean fuel trims to show up
Downstream O2's last 3 times as long(after Cat converters)
Exhaust manifold leaks suck in air so cause False Leans, computer is running engine Richer than it should because of this leak
Exhaust leaks after Upstream O2's don't effect engine operation