Hello All, I have a 98 F150 4.6(W) with 225,000+ miles on it. 2 days ago going to lunch the truck started missing real bad. CEL started flashing then stayed on. Pulled a code P0303 Misfire cylinder 3. Pulled the #3 plug and it was wet with anti-freeze( plugs and wires 2 months old).The truck does not blow white smoke and the oil is clean.I did the old test of starting the truck cold with the reservoir cap off and no bubbling or shooting out anti-freeze so I don't "think" it's a head gasket but maybe a intake manifold gasket. Any thought's or suggestions would be appreciated. Also is this hard to replace for a DIY'er ?

 

if it was #4 i would guess intake gasket, but being #3 i would do a leak down test and a coolant system pressure test. also. if your boot on the plug is bad, it will let moisture in, although you said it was a/f, so maybe the a/f is migrating toward the #3 but its pretty hard for liquid to run uphill to get to the hole

 

You might wanna check these lines as well , they have been known to leak - sometimes it's hard to tell .. The only givaway that told me they were is that there will be a small puddle on top of the COP(#4 or even # 3) or there will be a water stain where water has sat there in the past.

 

[QUOTE=jbrew]You might wanna check these lines as well , they have been known to leak - sometimes it's hard to tell .. The only givaway that told me they were is that there will be a small puddle on top of the COP(#4 or even # 3) or there will be a water stain where water has sat there in the past.

Mine does not have the COP's just the 2 coil packs. 2 months ago when I changed the plugs and wires I blew out all the plug wells after I pulled the boots and # 3 had somekind of liquid in it so it just might be a heater hose.But can that seep to the end of the plug and get it wet? (at the electrode)

 

if it was #4 i would guess intake gasket, but being #3 i would do a leak down test and a coolant system pressure test. also. if your boot on the plug is bad, it will let moisture in, although you said it was a/f, so maybe the a/f is migrating toward the #3 but its pretty hard for liquid to run uphill to get to the hole


s1037s,Couldn't it leak over #3 ?

 

If you have a pressure tester, you can usually catch leaking 4.6 intake gaskets with the engine cold. Coolant in the plug wells of a 4.6 is caused by leaking intake gaskets, 99 times out of 100.

 

[QUOTE=Lou Colmo]
Oh duhh, My bad .. I was thinking you had COPS

 

Thanks for the help everyone, At least it seems it's not the head gasket
How hard is a intake gasket to change or how much should it cost ? Thanks

 

take you about two hours to change the intake gasket yourself in the driveway. yes the hose could be leaking over # 3, sorry.

 

Absolutely nothing to be sorry about, I appreciate all the help very much.