[bogeysmith]

Hello;
I have a 01 Sable with the Duratec with about 148k miles. It has been running real rough and the CEL came on. The codes are P0401 and P0300.

It is worse when cold and when the A\C is on. It seems to run ok at highway speed and I can even use the a\c at highway speed. Around town it runs too rough with the A\C on.

I did find a vacuum leak. One of the elbows on the back valve cover was cracked.

I checked the plugs and the middle plug, along the front bank, showed a lot of brown colored moisture on the plug and in the spark plug hole \ wire. The other two plugs and wire were dry and in good condition.

I recently had low coolant come on and I am thinking it may be a head gasket.

I am planning on pulling the back plugs also to check.

Any help would be greatly appreciated.

 

[KhanTyranitar]

I think you are probably right. Has the coolant gotten into the oil? If the oil is clean, you can move forward with just doing the head. Just so you know, the head gasket can fail if the engine has ever been overheated, so it doesn't have to have been a recent event.