Ok guys, i have a problem with my 2000 Navigator with a 5.4L 32V DOHC.
A few weeks ago I took a trip towing my enclosed trailer that was about 3000lbs. On uphills, the truck would bog down and thought it would die before hitting the top. It had no power! At first I thought it was the tranny because I would get kicks when i had the cruise on and also when i put the pedal to the floor, it would kind of slow down instead of accelerate.

I got the service engine light and was able to pull 0171 and 0174 (System too lean), but since then they never came back on since I erased them that day. I still feel it though and the gas mileage is terrible! I am getting 6-7miles/gal according to the onboard computer. Being in Canada at $1.05/liter, its costing me a bundle and need a full tank just for the weekend.

I have checked for vacuum leaks, but can not find anything. The engine is less than a year old, including intake, sensors, hoses, etc....so I am quite stomped.

Any help or pointers in the right direction would be greatly appreciated.

 

One piece of information that may help with the search is what is new on your engine? If you have aftermarket parts...such as intake...exaust etc. How is your engine new w/ a 2000?
~Phil

 

intake is new and complete engine with sensors, etc. I bought a new crate engine and had someone put it in. Exhaust is same and so are the o2 Sensors, I guess since the manifold are the original ones. No aftermarket parts at all.

 

Anyone pelase???

 

You most likely have a vacuum leak. All the standard troubleshooting steps apply.

Find a shop with a smoke machine, the speed of finding the leak will make the diagnostic fee worthwhile if you don't wish to go the old route.

If not a vacuum leak, a faulty, dirty, mis-calibrated MAF sensor will also cause this fault.

Steve

Steve

 

Most common place for a vacuum leak on a 5.4 4V is on top of the intake, under the plastic trim that covers the throttle linkage. There'll be a 90 degree vacuum elbow that plugs directly into the intake manifold.

 

I checked the common places for a leak and could not find anything. All hoses are about 10 months old from when the engine was changed. I will check more or bring it to a place to have it checked. Can the catalysers cause this?