Another issue I have been battling for a few years is engine vibration at idle when warm. Ive got the 3.0 with what i think is 260k miles and still running strong. Last year i replaced heads because worn valve seats. Ive done everything i can think of to cure the vibration including new motor mounts. The engine runs fairly well and has no codes and fuel trims all in decent thresholds. No more than 5% on trims. The ignition system is new with a ford coil, new wires, plugs last year with no change. Fuel injecters were first pulled and cleaned, than i just replaced all of them. Again no changes. No vacuum leaks, MAF shows within range along with air temp. Coolant sensor is accurate. The only thing i havent done is a compression check because my dang harbor frieght tool is junk and i cant get fitting screwed on each spark plug hole.

Could unequal compression across cyl really cause a bad vibration at idle? It vibrates when engine is hot so engine is in closed loop but i dont think its anything related to engine managment (fuel, evap, air, etc). It doesnt use oil at all and has decent power. No knocking or bearing noises. Checked firing order and coil wire placement.

Is the 3.0 Duratec an imbalanced engine to begin with? Should i check compression across all cyl? Harmonic balancer replacement (although i dont see any inbalance visually)?

 

You have a 3.0l OHV Vulcan engine
Durtecs are DOHC and were never used in Rangers just Taurus/Sables

Yes, lower compression in one or two cylinders can cause a vibration at idle, same as a misfire can but its a partial misfire, but this should show up as P0300/P0316 code, or a specific misfire code, P0301-P0306

Check the fan clutch for wobble, engine off, lol
The fan clutch only locks after radiator warms up so if there is an out of balance blade or clutch it might only show up after warm up

 

I hadnt checked fuel trims in a while and decided to do that today and noticed bank 2 is running way lean. Checked upstream O2 sensor and its all over the place in terms of voltage so this means its going bad. Replacing this should fix my issue. Sometimes....its the easist things...

 

Replaced driver side O2 sensor and seems a little better. But vibration is still there. Im interested in the fan clutch idea. And here is why. Ever since I got the truck, the fan noise is very loud. Ive replaced the water pump, fan, and clutch with new units and its still loud. I think the only versions that are available are the tow package or super cooling. This causes the fan to be super noisy. Ive had trouble trying to find the stock clutch where it has less fins on the body of the clutch. Seems everywhere i look, its only super cooling version. I guess my next step should be removing the serpentine belt after its warmed up and see if vibration goes away...

Im not really keen on moving to electric fan. Wish there was some way to get the stock standard cooling clutch/fan setup for this 3.0.