Its been many many moons since my last post but I know there are some long time posters here that must have experienced this issue. Sorry for the length but I like to give all the details....and I type fast lol.
I have a 99 EXP with the 5.4 that I just picked up. It sat for a while after needing a radiator. The PO while filling up the old radiator to show it to me spilled some water and for a while it was hard to start. After a lil bit of time that issue kinda went away but it still would take a few seconds to start. While test driving it vibed and shuddered feeling like plugs/wires were needed so I put that on my list of needs to take care of after purchase. Fast forward to today...
I've replaced the radiator, and after plugging into a snap-on scanner found a misfire on #3. No SES light but the scanner read each cylinder like a heart monitor and all was good except for #3 which was all over the map. So I ran out and picked up a coil and plug and dove into the #3. There were some PCV lines and heater hoses in the way that my big A hands had to manuver and move alot. Along the way I found a hole in some of the pcv elbows and replaced them with sparkplug boots for the time being. I replaced the plug and coil and BOOM truck ran smooth. . Took the truck to the local car wash and cleaned the inside feeling pretty good about myself and waited for wife and kids to get home to present her with her new(to us) wheels. As were riding out to dinner the truck starts to miss again around 40 and then again between 50-60mph. Of course wife is now giving me "the look". We get home and upon exiting we smell smoke. I look under the hood and see a good bit of smoke coming from the area of the PCV/heater hose/#3 area. I did some wiggling of the pcv and test drove again and seems the smoke lessened but didnt go away completely.
So to summarize I still have a miss just no where near as bad as it was before. I can accelerate from a stop smoothly up to 50 before it becomes noticable or to about 40 and coast and you can feel a miss then at 50-60 it gets more pronounced. Its also kinda hard to start taking sometimes 5-6 seconds before it catches. And lastly I have some smoke coming from under the hood from the rear passenger side. OH and I noticed my temp gauge rising after my drive last night so I turned on the heat and it dropped immediately but the heat was just warm not hot....Whew..ok thats it. Please help! I need to get this thing right before I put wife/kids in it.
I would get a telescopic inspection mirror and a good beam flashlight and lean over the engine and look at the passenger head along the intake manifold where it meets the head, by injectors and cops and to the rear by the heater hoses for a coolant leak
update I just found that I have oil leaking on the my catalytic converter and I'm assuming that it's coming from my head gasket. after doing some searching im seeing this is a regular problem and I'm wondering if there are any sealing products that will help slow this down for the time being?
an oil leak like that would usually be from the valve cover gasket, not the head gasket - a much smaller job!! pull the darn thing off, clean it, and replace the gasket, preferably on both sides of the engine
I have oil on my trans bell housing and starter tho...from what ive found this is a hg issue based on design. Ill look deeper tomorrow but if this IS the problem then is ot just about keeping the oil level up or are there other repercussions I need to look out for?
the all history of v8 engines, valve cover leaks have been common, primarily leaking right on the mainfold and smoking off, with some coming out the ends and running down in different places. i haven't studied the 5.4 as close as some of the older engines, but if it is the HG, i would assume its the high pressure gallery that delivers oil to the head (as opposed to where oil drips back down). if yes, the big fear is that it may suddenly blow out, seeing that its already weakened, and cause a sudden loss of oil, which you may not notice until its too late.
if its just valve cover, i've seen them get bad enough that you stop the car and notice smoke all around you because it was leaking so much, but had no other ill effects.