Trouble Codes

[DougH]

I have to trouble codes popping up. The first code is p0125. The second code is p0306. The second code is cylinder 6 misfire detected. I've changed my spark plugs and wires, the coil pack ,my fuel filter, I've had the injectors cleaned, oil changed and I'm having a problem with the fuel system coughing and sputtering. If idles really ruff, and sometimes when I put my foot in it, it just shakes. On the first code is insufficient coolant temperature for closed-loop fuel control. I have changed thermostat sensor there's nothing wrong with the thermostat so I I'm trying to find out what could be the problem. Any input would be appreciated thank you.

 

[adsm08]

How do you know there is nothing wrong with the thermostat?

 

[Dirtman]

Run a compression and leakdown test. Cylinder 6 is probably low/leaking because of the exhaust valve.