Hey everyone, I am new here and this is my first thread but i have a problem with this truck(99 F150 XL 4x4 4.2 ltr. V6 148,000 miles) I just bought this truck and the first problem i noticed was a bad miss and exhaust leak, Well after replacing the plugs and going to a muffler shop and replacing the muffler it did not solve the leak problem so i took it to another shop and they told me my driver side cat was falling apart and the guts were coming out of it, Well thats strange because that is the side of the engine which had the fouled plugs on it, So im in the process of putting magnaflow hi flo cats on it but after pulling out the plugs i noticed just a very tiny bit of what smells like coolant on the front engine cylinder threads and on the back driver side cylinder threads and engine also has a little white smoke at start up,but uses very little coolant but it does use some, and there is still a small miss only at idle! Note:There is no check engine light and the truck does not burn any oil at all. I changed the oil twice since i bought it just to check but i did notice a little what looked like brown foam where the oil was draining into the drain pan but just a little .Also the truck is not reaching its full power potential and should do better pulling hills and accelerating. I would really would like to diagnose and fix the problem before putting on the new cats. Im thinking it may have an internal intake gasket leaking because there are no signs externally and i tried the carb cleaner trick! If you have any ideas i would appreciate your advice!!! Thanks

 

The carb cleaner trick is merely to find vacuum leaks and that idea is virtually obsolete nowadays. Simply doesn't work as it used to. Smoke machine is king.

The fouled plugs will cause a rich condition which will overcook the cat and cause it to fail prematurely. So, one problem caused another. Now that you have that fixed it sounds like you have a leaking head gasket. Any coolant in the cylinder is a sure sign of this. Your engine shouldn't use any coolant. This isn't an item that gets topped off regularly like oil would. White smoke is a sign, but that it's only in the morning is normal for most engines anyway. Lack of power too? Yeah, sounds like a head gasket going south on you.

What you need is a pressure test to determine cylinder pressures to start with. This will give you an idea of what's going wrong and where. You can also pressurize the cylinder and see where the air leaks to.

Brown milkshake lookin residue on the oil cap is normal. Anywhere else means you have water/coolant in the engine.

Hope this helps.

 

I had a real bad problem with loss of power. None of the other issues you are having though. I changed the coil pack and it made a tremendous difference. If you haven't already I would highly recommend changing it or at least have a shop check it out. Luckily on the 4.2 there is one coil pack that houses all the coils unlike the 8's which have one on each cylinder. Much cheaper.

 

Thanks for the help i greatly appreciate it and i will look into it. And about the head gasket thing. It seemed like the engine did not start smoking right away, it took a couple minutes and it really smelled like fuel(Not like coolant), also the engine seems to run really cool and not like any other vehicle i have had with a bad or going bad head gasket(Uses no oil), but i will definitely look into it>> Thanks for your time!!!