MRkoehl1

so im having issues with my 07 4.6. i have 241k miles on the body and 50k on the motor. i am misfiring at idle but not driving. i cant get over 3500 rpm. my cats were clogged so i gutted them it ran fine for about an hour then started misfiring again at idle. im eating oil like crazy but no leaks. any idea of what can be causing these issues

Jaryd21

Did you check the plug, if not I would check them but be careful they are two piece and could be a pain in the butt.

Bert

yeah just a crazy wild guess -- but maybe the oil is going out the exhaust, and fouling the plugs on its way through?

and just 'cause it is easy to do -- clean the MAF sensor, if not cleaned recently (use the CRC spray cleaner made specifically for that)

houtex

Quote:

im eating oil like crazy but no leaks

Could be a few things, but that'd definitely be the issue. Oil not on ground, but going AWOL, and the thing is misfiring indicates highly that the oil is getting into a cylinder (or more?) and being burned/pushed through into the exhaust, which explains the plugged up cats. Causes are valve stem seal(s) is/are bad. Blown head gasket perhaps. Warped head/deck is a possiblie thing. Rings of the pistons shot. Or a scored up cylinder wall or possibly cracked piston... 50K on the motor doesn't matter, these things happen for whatever reason, nothing's perfect.

As mentioned, pulling the plugs is advised, they'll tell you a lot. If one's all oiled up, that cylinder/head needs to be looked at. I'd also look at smelling the coolant after the car cools down, or looking at it to see if it's got oil in it, as it could be going there too, but I'm thinkin' not. I'm thinkin' that engine situation is exactly (inexactly) what I say: Oil in the cylinder(s).

If you can get a small enough endoscope to stick in the spark plug hole of whatever plug(s) that had oil on them (I almost guarantee one or more do) then you can maybe see if the piston is ok, the walls aren't scored, and if it's fancy enough, inspect the valves or even see if there's any way the head gasket let oil in. You may find the source of the leak by just seeing it running down the cylinder wall.

Whatever the case, this is probably a teardown of some sort. Probably head(s) off, but I'm a bit afeared the piston/rings/cylinder may be compromised, which means engine out rebuild. Maybe 'just' re-ring, but probably more... even up to engine block is toast, replace the engine.

All that is if there's oil on the plugs (which again, I'm sayin' that's gonna be it.) But if there's not, great! Still a oil mystery. You need to get a good scan tool on it for sure at that point, but you *really* need to find that missing oil, and pronto... and at this point, I'm not sure what the heck it'd be, because that doesn't even sound possible if the oil just poofs away...

That all, of course, is a bunch of guesses from *way way* over here, so grains of salt are to be taken. If you're not mechanically inclined for these types of things, you'd be better off looking for a good mechanic to properly diagnose this and give you the un-great to really (siphon with a large amount of negative pressure) news.

Nonetheless I do hope this helps in some way. And welcome to the forums!

/I only mention this post because spark plugs on that car are a *PILL* if they've not been out and done right the second time. You need to know if you don't: https://themustangsource.com/forums/...-plugs-522706/