Several issues can cause a rough idle: the EGR (if equipped) can be sticking, causing exhaust gases to be entering the intake during idle. You don't want to bypass the EGR or remove it, as it helps prevent pinging during above idle driving by helping cool the cylinders. There's a simple test that can be done if the EGR is suspect, and a search on this 3.0 forum will help you; it's most likely on this same page of posts, as it was discussed the past two weeks. The DPFE sensor is a known issue, but will usually provide a P0401 or P0402 CEL code (Check Engine Light).
The idle control valve is another item to check for poor idle. Many, many helpful posts on this within this site.
Any vacuum hose leaks will cause poor idle, as unmetered air is entering the intake, throwing off the MAF (mass airflow sensor) readings.
Dirty air filter, bad or worn spark plugs, bad plug wires, are also culprits.
Cam Position sensor is another. Again, great write-ups on this on this site.
And yes, there is no reason why it cannot "run like new"; my 2000 Ranger with it's 3.0 has 216K on it; runs and drives great!
As to degreasing an engine, be very, very careful when washing off the engine after degreaser has been applied. Water and the various sensors DO NOT MIX well. Cover all electrical connectios and sensors good before spraying water onto the engine. Follow the directions of the degreaser (warm the engine, spray on the degreaser).
Last edited by bucko; 12-08-2014 at 05:18 AM.