Originally Posted By: jk_636
Originally Posted By: chartrue2
‘06 Taurus. Bought used two months ago. 157K miles. Looks and usually runs well. CEL keeps coming on for P304–misfire on cylinder four. Shop says it needs head gasket for about $1K in repairs. Paid $2K for the car. Won’t sell it with defect in good conscience. Should I put money in to this or cut my losses?
Is the only reason you believe it to need a head gasket because your mechanic told you so? Have you checked the coolant levels? Is it overheating? Water running out of the tail pipe? Blowing steam going down the road? Did you pull plug #4 and inspect it?
P0304 alone could indicate any of several possible problems, and I would definitely do some more investigation on my own before blindly trusting the mechanic.
https://repairpal.com/OBD-II-Code-P0304
I would hate for you to be taken for a $1k ride by an unscrupulous mechanic when you may have only needed something simple like a plug or coil.
If it does end up being a head gasket, you may want to dedicate a weekend to changing the head gasket yourself or try some blue devil.
https://store.gobdp.com/head-gasket-sealer-directions/
That. Make sure it's ACTUALLY a head gasket. If it's the Vulcan (OHV) engine, those are all cast-iron and plenty tough. If it's a Duratec (DOHC 24V), those aren't forgiving of overheating, but not really known for head gaskets.
A misfire could be something as simple as a bad plug, coil, a plug wire, or even a vacuum leak.
First, check the spark plug. If it looks good, swap the plug wire on #4 to a different cylinder. Misfire goes with it? Change the plug wires. (If they're original, they're past due for changing anyway.)