Hell all, long time reader but finally decided to join. I love my ranger have a few of them and just want to get some opinions on what I should do with my 03.
2003 Ranger 2wd 3.0 flex fuel. Has the well known rough idle, new coil pack, plugs and wires Motorcraft coil pack and wires with auto lite double plat spark plugs. Also new fuel pump, and replaced/ tested IAC, MAF, purge solenion and vent valve. No Vacuum leaks, (atleast what I can find with spraying starting fluid near hoses and intakes. Also noticed that the fuel injectors on bank 2 sound louder then bank 1, why might that be? I did have a lean bank 1 code but sense replacing the coil pack it has not returned. After all this i finally decided that it was time for a compression test. These are my results.
1- 160
2-130
3-150
4-160
5-165
6- 160

Have not done a leak down test on cylinder two yet. Do y’all think that cylinder 2 could be causing this rough idle? Is it too low? I understand I need to do the leak down test but I have a feeling that the valves are seating like on most of these 3.0s I’ve read on here.

 

Yes, #2 has a burnt valve, #3 has as well

You don't need to do a leak down test, just use a "straw" to put some oil in the spark plug hole and retest
Like a teaspoon of oil
Dip straw in oil bottle, put finger over the top of straw and pull it out, put straw in the hole and remove finger

Compression WILL go up, as the oil seals the rings........but not the valves, so if it doesn't go up passed the 165 then a valve is the issue

Yes, low compression causes a misfire
And you are doing a static compression test, cranking engine not running engine
Running compression is about 40% lower than static compression

Burnt Exhaust Valves are about the most common of the basic mechanical engine issues
Exhaust valves run HOT, intake valves are cooled by incoming air and fuel so don't get HOT, but do get warm, lol

Valves and their seats are lapped to matching angles get a good seal
Valves rotate each time they open to avoid getting HOT spots
If there is a spot where angle doesn't quite line up then it starts a HOT spot, where the 1,200+ deg gases from ignition can force their way out, this "burns" the valve
Once it starts................it just gets worse over time, which is why I think #3 is on its way as well

The 2004-2006 3.0ls did have a TSB about recessed Exhaust Valve seats, manufacturing error, but never covered by warranty because it didn't show up that soon if I remember correctly
2003 was never mentioned but.....................I would suspect 2003 and 2007 3.0ls

In any case BOTH heads need to be done at the same time
A valve job or new heads, that's up to you

 

@RonD Ahh I gotcha, thank you for that. Very informational, I will do the oil test and get back to you with the results as soon as I have the chance. (Probably this weekend)

 

@RonD i did the compression test with all spark plugs out and while cranking with the gas pedal to the floor.

 

Now that's the PROPER WAY to do a compression test