I have an '01 QC SLT(4.7 auto with limited slip and 4W ABS) with 114,000 miles. I bought it new. A couple of things have started to happen lately that may or may not be related.
First, when the truck is cold (for about the first five minutes) it makes a sound similar to a vacuum leak at idle. If you give it just a little gas (or more) the sound goes away. A friend of mine said it might be the intake manifold gasket. Does this make any sense to anyone else? Other suggestions?
Second, mileage is down substantially over thepast 6-8 months - getting about 12 city and 17 highway. Before this I always got +/-14/20.
Third, the truck smokes and has strong oil burning smell if you turn it off for about 10 -15 minutes and then restart it. No smoke in the mornings when cold. I have had friends follow me and they don't see or smell smoke while driving. Suggestions? I'm getting frustrated and thinking about trading.

 

My dakota has the same vacuum leak. Dont worry about it. I took it to a friend and he did tests on it with a scanner and it came us as something the dodge put on for basicly no reason. (OE does it all the time) It is just a little hose. About the gas milage, mine goes down in the winter months too. But since it has been more then just winter i would do a tune up on it, plugs, wires, cap and rotor and tire pressure. About the oil burning smell and smoke, go down to the local parts store and get yourself some ATF and put about a quart of it in your engine oil. I know I know your thinking Auto Trans Fluid in my oil? Well ATF is oil just as your engine oil is but refined more. It acts as a detergant in your oiling system too. If you ever open up a Auto trans it is perfectly clean no matter how old it is. Run the ATF in your truck for about 500 miles. Then change your oil, (it will be the blackest oil you have ever seen because the ATF cleaned out your motor) then put what ever oil you always use back in the truck. Last step put a bottle of Restore in your Oil and after a couple hundred miles your truck will not smoke anymore and will regain some compression.

If you have any questions let me know.

 

Have to disagree with dak726 on ATF in the oil. Never known this to be a good idea. Try using Marvel Mystery Oil. You can even buy it at WalMart and I believe you can get the same response from it that Dak726 is thinking with ATF, but Marvel is safe to put in your oil. I would also put it in your fuel, which is also safe and it should deffinatly help with the fuel milage drop.

 

DAK736 - Where is the little hose that is leaking? I'd like to find it and plug it or replace it.

 

Im pritty sure that the leak is on the passenger side around the back of the intake. And about the ATF it works great, i have known many mechanics to use it and many instructors at Wyotech, ATC, and UTI to back it up. But using Marvel Mystery Oil will do the same thing, from what i hear, i have never done it my self.

 

In my opinion since there is no apparent smoking from the exhaust and the burning smell lasts for 10 to 15 minutes AFTER the engine is shut off that there must be an oil leak somewhere. It is VERY possible that the intake is leaking since mileage is also down. First things first though. Begin by checking ALL the vacuum hoses in the engine compartment as they will become brittle and crack with age. Next check around the base of the valve covers for signs of leakage as leaking valve cover(s) will definately leak onto the exhaust manifolds and cause the burning smell. For the next part an extendable mirror will be handy or just get under the truck. Position the mirror at the firewall and angle it so you can see the back of the intake. Some added light will help matters. Now just look for signs of oil leakage. I kinda prefer the under the truck method because it gives me the opportunity to check out other things as well. Lying on your back feet to the front, run your hand up the transmission bellhousing next to the engine. You'll have to stretch a ways and do this on both sides. If the intake is leaking at the back you will most definately come back with one or both hands oily. Also while you are under there look back towards the rest of the undercarriage and look for oil spray on the surfaces of different things . This will give you an indication of where and how much is leaking. With a little detective work you'll find the leak and I think it is a leak. As for the vacuum leak sound I also have a 2001 Dak QC and when cold I hear a faint whistling. Listen closely....... mine comes from the dash. I also think that there is a TSB out about this occurence. Some thing to do with the heater blend door. It's not a big issue I just ignore it or turn up the radio till the truck warms up. In all likelyhood the oil burning smell and the whistling sound you hear are unrelated. I think you almost surely have either a valve cover or an intake leaking though. Good luck!