New user here :D I have a 02 Ranger 3.0L 4x2 with 175k miles. I mostly feel the vibration when sitting in Park or at a stop light. I can also visibly see it on the steering wheel. No CEL either.
I have cleaned the MAF sensor, Throttle Body, IAC valve. Changed the PCV valve, spark plugs, Wires, ignition coil, air filter, and the fuel filter. And nothing has made a difference. I even threw in a bottle of STP fuel injector cleaner from a gas station hoping my problem would magically go away lol.
Now, the truck runs fine and have seen an increase in MPG since changing said parts. The RPMs don't fluctuate up or down or has never stalled on me and the truck starts perfectly every time in hot or cold.

There's 3 things though I have noticed since owning the truck that I hope might be the culprit for my engine vibrating.
1. I have found an unplugged connector by the ATF dipstick that runs into a wire harness that I don't know what it's for. I can't seem to find where it connvects to


2. A bolt for the ignition coil is missing. Sounds dumb i know, but maybe the coil pack isn't properly grounded? The first bolt I took off when changing the coil pack did feel pressurized, it even squirted out what smelled like fuel. Strange I know.
3. When ever I turn the AC on, the air flow is very weak. I read it's common in these trucks for a vac line near the manifold that runs into the cabin to break and can affect the airflow of the AC. there's a video on YouTube about it that I can't find at the moment. I haven't thoroughly looked at mine but it did seem fine.

I plan on changing the motor and transmission mounts soon but after that i'll be clueless on what to look for next. If anyone can help me It would be very appreciated!

Oh and the MAF sensor seems to have some black specs I couldn't clean off of with the MAF cleaner. I'll put a picture up when I have the chance.

 

Welcome to the forum

When engine is COLD, loosen fan belt and remove it from Crank Pulley
Start engine
battery light will stay on thats OK
See if vibration is gone
You can run a COLD engine for about 2 minutes without water pump, NO LONGER!!!

Fan Clutch can cause vibration, power steering pump as well, both will be stopped with no fan belt.


Motor mounts
Open hood
Start engine, fan belt is back on
Assume automatic trans
Shift into Reverse
Leave foot on the brake and press down on gas pedal a little
Watch engine, it will move slightly up on one side
let off gas pedal, if you hear a clunk then mount is broken
Repeat but put trans in Drive, other side of engine will lift up

If you have a manual trans you can do the same test but set Parking brake so truck can't move while you let out clutch pedal and watch engine lift up, on one side then the other.

2. Coil pack doesn't need to be grounded persay, it's 4 wires are 1-12v and 3-Grounds

3. vents in the cab dash are vacuum controlled, but they set Direction of air flow, not speed of air flow.
Defrost, Panel, and Floor are the 3 directions air can flow
Defrost is selected when there is no or low vacuum, it is Default

So turn Fan to High, if you select panel or floor and defrost vent still has air flowing out of it then yes, vacuum in the cab is low, and the Vacuum line to Vacuum reservoir could be leaking or Vacuum reservoir is

Speed of the air is set by Fan Speed, fan motor.

AC on or off just turns on compressor in engine bay, has nothing to do with air vents or flow.
MAX AC does close outside air vent, but again nothing to do with air flowing out of the vents

 

Thanks a ton, will definitely give these a try this weekend and yes it's an automatic. The power steering is really loud and whiney even after I flushed the fluid. So hopefully that's the problem

Also, anything on that unplugged connector I found?

 

No, connector doesn't ring a bell with me.

Many Rangers are wired for all options, could be for cruise control if you don't have that, 4 wheel ABS?

With the shielding I would assume it would run under the vehicle, but............as said doesn't ring a bell.
Flex Fuel Rangers did have a fuel type sensor by the fuel filter under drivers seat area of frame rail

 

Ok I believe my truck came with cruise control but the buttons on the steering wheel were broken and ripped off by the previous owner and the horn doesn't work so it's probably related to that lol. And it's also flex fuel so I'll look out for the sensor.

I haven't tried the suggestions yet and i now suspect either a small vacuum leak or a faulty sensor. Sometimes when I start the truck the RPMs shoot up and idles at 1600-2000 for about a minute and slowly goes down. Is there any common leaks in these trucks that I should look out for? I have some carb cleaner so I'll give that a try this weekend also.

And here's the video I mentioned in the OP if anyone is interested https://youtu.be/7diy1pxfDwA

 

Cold or warm start should get a REV from the engine, thats common for most fuel injection engines, they all use an IAC(idle air control) Valve to set idle levels.

When you turn on the key the computer boots up and will open IAC Valve(Fords name for it) all the way, which would be about a 1,800rpm idle
As soon as engine starts, RPMS above 400, computer will then start to close the IAC Valve to set "target idle", so a high REV up then a drop of RPM
Target idle is based on engine/coolant temperature, using ECT(engine coolant temp) sensor.
Cold engine idle would be at least 1,100rpm, depends on outside temp
Warm idle is 650 for manual trans, 750 for automatics, 4cyl engines about 50rpm higher
Idle slowly comes down as engine/coolant warms up

If idle is hanging high at 1,800 or so then I would Clean the IAC Valve first, could just be sticking a bit at wide open
Thread with pictures here: How to: - IAC valve cleaning thread (w/pics) | Ford Explorer and Ford Ranger Forums - Serious Explorations

Sensors rarely fail but are often replaced, all can be tested, but you weigh that against replacement cost.

90% of DIY replaced sensors were working fine
50% of pro-mechanic replaced sensors were also working fine, but some of these were changed to pad the bill, lol.


Simple and free vacuum leak test
Warm up engine fully and let it idle
Unplug the 2 wire connector on the IAC Valve, it will close all the way
Engine idle should drop to 500rpm or engine may even stumble and die, either is GOOD, no vacuum leaks

If idle stays high then there is a vacuum leak

 

Thanks for the input and suggestions Ron I really appreciate it

One last thing, I've been keeping a closer eye on the RPMs and it does in fact fluctuate when stopped, but very little. Ive also noticed the vibration is more apparent when the engine is warm.

 

warm idle should not change more than 5rpms

So there may be partial misfires at idle the computer is compensating for, and that also causes vibration

 

Alright so I've been messing under the hood in my spare time tracing what ever vacuum line I come across and can't find anything that would indicate a leak. And the IAC is working as it should when I tried the test you posted. The engine starts fine but then starts to vibrate a minute or two after start up and you mentioned partial misfires could be the issue. If so, what causes partial misfires? Clogged ​
​or faulty fuel injectors? Fuel pump? Maybe bad intake manifold gaskets or plenum gaskets?

On another note, the heater control valve (2 port valve) is leaking a lil bit of coolant and there's a vac line that connects to it. I have that part coming in tomorrow to replace it but I don't think that's the problem. (Crossing my fingers) lol

​​​​​​​And last, the mass airflow sensor has two exposed wires that got chaffed over time I'll post the pictures below. I measured the resistance and it came up to 3.71 ohms and also tested it by unplugging it while the engine was running and it just about stalled on me so it's probably working as it should

 

I thought I posted a reply but I guess it never posted...

Anyways, the engine starts up fine and then starts to vibrate after a minute or two and you can visibly see it shaking. You mentioned partial misfires, what can cause this? Bad or faulty fuel injectors? Fuel pump? How do i rule out intake or plenum gaskets? I tested the IAC again and it almost stalled so that's working fine. The MAF sensor has 2 chaffed wires and has some dirt in there. I'll post the pics below. Idk if that could be the cause, I measured the resistance and it came to 3.71 ohms and I also unplugged it while the truck was running and it nearly stalled.
also my heater control valve (2 port valve) has a small coolant leak and I found a YouTube video where the guy explains his HCV was causing small vacuum leak enough to give it a rough idle. Part comes in tomorrow to replace it

​​​​​​​Will keep updated