Question about 'Sucked'/Stuck Valves

[dasfinc]

A few people have made casual mention that my mis-fire could be caused by a sucked/stuck valve. *4.0 OHV on a 00 Ranger*

I still do not believe this is the case, but am curious what are signs OF a sucked valve?

*My truck idles with only a SLIGHT vibration from its misfire, and drives fine over 2000RPM, and I still suspect a leaking/bad/probablyclogged injector*

 

[martin]

put a vacuum gauge on it, sticky valves have distinctive vacuum characteristics.

 

[adsm08]

A normally operating engine (even with a fuel or ignition miss) will hold a steady vac level at idle. A sticky valve will make the needle on the gauge jump as the dead cylinder doesn't produce the same amount of vacuum.

 

[dasfinc]

I never updated this one.

The 4.0 in my 2000 had PERFECT compression and Vac, Faulty coilpack was causing the symptoms

 

[adsm08]

I never updated this one.

The 4.0 in my 2000 had PERFECT compression and Vac, Faulty coilpack was causing the symptoms

That is a far more likely/common than a stuck or sucked valve.