Hi all,

I have a 2001 F150 4x4 supercrew XLT 4.6 with 150,000 miles. I have a few things happening in the truck, and although it is still running for now, I would like to get ahead of this before something catastrophic happens, and I don't know if everything is related, or everything is falling apart separately.

1. I have been noticing a burning smell coming from under the hood after driving, every time I drive, but no noticeable leaks, and oil level is fine. I have seen light smoke coming from the exhaust but inconsistently. A mechanic said it was probably the valve cover seals leaking to the manifold, but I would think there would eventually be less oil on the dipstick?

2. When on the gas, over 2200 RPMish, the air and AC switches to defrost. It seems like a vacuum line leak somewhere, but can't find it.

3. Generally, the truck seems sluggish, sometimes unwilling to shift gears or accelerate at freeway speeds. Not sure if its the transmission going out again (had it replaced at 125000), or spark plugs?

Any thoughts or suggestions where to start would be very appreciated.

 

My guess at 150k miles to check the CATS. If truck is sluggish like that the CATS may need replacing. When was the last time you changed out the tranny fluid or dropped the pan. That could be something to look at as well if it has never been changed. Start with that first and then troubleshoot from there. Let us know what you have done so we have a better idea.

 

1) Yes in all probability the valve covers are leaking. But... it could be that you have a intake manifold leak too, which may account for the sluggishness. A smoke test maybe needed to check for manifold leaks. At any rate, the leaks can tend to be on the firewall side and seep onto the exhaust and burn off and not leave a trail. To rule out Head gaskets, do a hydrocarbon test on your coolant. If exhaust gases are present in the coolant, then your issues are more extensive.

2) it could be a vacuum leak is present for your HACV ....here again a smoke test can help locate the leak. There are small vacuum lines for the HACV behind the battery...might want to trace them and see if you can seem anything obvious . Some of it maybe by design...that the ECM cuts off the A/C during hard acceleration for more ummph...IDK. The 2200 RPM threshold would seem pretty low for that to come into play.

3) the sluggishness....can be A LOT of things. Yes spark plugs are on that list. It can be from vacuum leaks too. Or clogged fuel filter or air filter.

the unwillingness to shift , 1st make sure your transmission fluid level is correct. I'd scan for codes both engine and transmission, see if anything pops up. It would not hurt to flush your radiator and or replace your trans cooler. ( trans cooler are difficult to flush, but maybe can be done with a lot of patience). It maybe that you just need some maintenance and many of your issues will go away, doesn't sound too serious.