04 Ranger 3.0L Gave 300,305 and 316 codes at 70K miles. After replacing injector, plugs, wires, and the idle sensor, compression test showed it was the # 5 cylinder. Got the heads rebuilt and was told it was sunken exhaust seats. Problem solved until this week.

Now 108K miles and codes 300,301, and 316 appear. Slight rough idle and it feels like the engine is holding back around 2000 rpm.

Any suggestions? Am I the only one having problems with the heads every few years?

Thanks!

 

Get a vacuum gauge or mity vac tester and see what it shows. Performance probe has
a tutorial to show you what the needle will look like for different problems (bad rings,
valve seat, weak springs, plugged exhaust etc.) Look under diagnostics in the sitemap
and read all the way through it then get the vac gauge and test your manifold vac readings. Also don't forget gas line dryer I would put at least 2 bottles in on 1/4 tank
or so, Water in the fuel will give a midrange deadspot!!