anyone out there ever have a 4.6L engine smoke after the vehicle has been shut off overnight or after a day at work when you first start it? it is starting to happen more frequently, the very first time it starts it smokes( it clears up pretty quick but looks like a combination of white/blue smoke.

the engine has no DTC"S per my OBD 2 scanner and the gas milelage has been what it was when I bought it. one I pull away and step on it one small puff and its all over its gone. I have noticed the rpms fluctuating up and down when this happens so im thinking there is extra fuel in there or being put in there at startup???? the truck runs fine otherwise. im keeping an eye on this but not sure where to look.

sounds like bad valve seals. you may try cleanning your pvc valve or just get a new one they are cheep

I was alsthink about the cheapest first which would be pcv valve how long has it been since its been replaced

it's either your valvue seals or your piston rings, most likely the seals.

preform a compression test on the engine to determine what's losing pressure.

to check if it the vavle seals, remove the head and fill the ports with oil. and the oil galleries above the seals. leave this sitting about 6 inches above something, like a tupperware lid or whatever. if in the morning there's oil leaked through the valves are your problem. try this again with oil only in either the ports or above the seals, this will tell you which one it is.

if there's no leakage from the head it's either the rings/bore or the head gasket. it's a good idea to change the head gasket anyway, jusr regular maintenance. you'll need to measure the bore to see if it's oval'd. if not, it's the rings.

thanks, I did check the valve seemed fine but since its intermittent and its cheap to replace I will change it. ive taken good care of this truck and cant believe the valve seals are bad already but you never know. I will check out the vacuum system with a gauge and see what the needle does. the truck runs fine and gets great gas mileage so im iffy on the rings. may have to wait till it gets worse. thanks, I will start checking into it more and get back to ya all.

The puff of BLUE smoke is OIL, most likely due to one leaking valve stem seal. Do not be worried about it, while very uncommon on 1996 and newer 4.6L engines it can hapen if the PCV system is not operating properly for an extended period (early 4.6Ls had "hard" stem seals that would get too stiff to seal with high heat and time). I have NEVER seen a 4.6L that was "worn out", but anything can happen given enough abuse and time.

You idle issue is likely the "IAC" or Idle Air Control, they get sticky with age. Simple and relatively cheap to replace. Please use ONLY a factory part, unless you really like doing it.

You can change valve seals by turning the engine until both valves are shut.
Then use a compression tester hose remove the valve and hook up to an air hose. You can then compress the spring and remove the keepers. Then I would use umbrella seals from a machine shop. You can do one cylinder at a time. I would estimate 4 hrs to do the job.

You can change valve seals by turning the engine until both valves are shut.
Then use a compression tester hose remove the valve and hook up to an air hose. You can then compress the spring and remove the keepers.

what?

you use a valve spring compressor to firstly compress the springs, then you remove the keeper/retainers. it requires the cylinder head to be removed.

i have never once heard of a method like the one you descried. nor did i understand any of it. how the hell do you plan to remove a valve with the hose from a compression gauge?

First you are not removing the valve you are installing new seals. If you never worked on an engine you won't understand. The valve goes in from the bottom then the seal fits on top of the seat for the valve. Umbrella means it is shaped like an umbrella. As the valves up and down this seal sits above the seat. Oil runs down the valve stem and the seal prevents it from running into the cylinder.
The air in the cylinder keeps the valve closed so you can install the seals. Otherwise the valves will drop out.

First you are not removing the valve you are installing new seals. If you never worked on an engine you won't understand. The valve goes in from the bottom then the seal fits on top of the seat for the valve. Umbrella means it is shaped like an umbrella. As the valves up and down this seal sits above the seat. Oil runs down the valve stem and the seal prevents it from running into the cylinder.
The air in the cylinder keeps the valve closed so you can install the seals. Otherwise the valves will drop out.

i've worked on many an engine, maybe i didn't understand your method because 1, it wasn't clear and 2 i've only replaced those parts when doing a full tear-down and rebuild job.

If you ever have a broken valve spring try it as it is a lot cheaper than a tear down. All you are doing is putting shop air pressure in the cylinder with the valves closed and maintaining it until done. If you have one square inch of exposed valve and 150psi shop pressure in the cylinder pushing against the valve the valve won't drop out.

I have used this method before in emergencies, although i dont like too. When you break a valve spring at the racetrack though, you need to get it fixed quick sometimes. Just make sure you have the piston at TDC , and secure the crankshaft where it cant turn. (vice grips clamped to a pulley, pullhandle and socket on the crank bolt, ......) Because the air pressure can force the piston back down. This is just for saftey, in case you lose air pressure for some reason, the valve wont drop thru on top of the piston, ive seen it happen. They make special valve spring compressors for this purpose.(around 30$) Also be careful you dont fumblefinger one of the keepers and lose it, or worse, drop it down in the engine, ive seen that happen too.

Now back to jwj2357`s original question. You said the smoke was white/blue. If you are getting a little oil past the valve stem seals, i wouldnt worry about it , unless it really bugs you, or it gets to the point youre having to add alot of oil. If its white smoke, it could be coolant getting into a combustion chamber from a cracked head, head gasket seeping somewhere. It seeps in while it sits overnight, and you get a puff of steam when you first start it. Try a bottle of Bars Leaks, and see if that stops it. If its a coolant leak, it usually works, and is good to stop seeps and leaks in other areas.

since it's on the startup i'm going to say it's probably a vavle guide seal. with the seals leaking oil drips down onto the valves while the engine's running, then whe it's started they open and the oil goes into the chamber and burns.

if it was smoking constantly while running, i'd say it's more likely to be the rings.