Please bare with me, I don't know all that much about cars (ya ya, woman driver here ...) So try to be nice! I have a 2001 V6 3.8L with 115k. I had some overheating problems some months back but fixed it with the changing of a sensor (not sure if that could be related at all). A couple months back, I hit a good bump and ripped off part of my exhaust and had it fixed with a new pipe (ya.... i know). Ever since then, my b/f seems to think I have a manifold (header?) leak because he can "hear the leak" and I've had terrible gas mileage since then. When I'm talking bad gas mileage, I'm talking like 260-280 kms (160-180miles) to a tank when driving in the city, when before I was getting about 500-550kms to a tank when I first bought it a year ago. Could an exhaust leak cause me to have such a terrible loss in fuel ? There are no visible leaks or holes that we've seen. This is what I've ruled out so far
1) Spark plugs newly changed
2) Fuel filter changed
3) Air filter changed
4) Oil recently changed
I've read a lot about it being maybe an O2 sensor, but I also read that if it were my o2 sensor, it would throw a code at me but I haven't had any engine light or anything. What could be my possibilities at this point? Bad wires? Exhaust leak? I have no idea... I'm stumped. My car also vibrates sometimes and makes weird noises, like a gurgling noise when you turn the car off which seems to be coming from around the passenger side, but who knows. My engine has felt boggy and not at its full potential ever since I got it, so I don't really know how it SHOULD feel. It also jumps randomly when the gears are shifting (it's auto). Any help at all would be appreciated... I don't feel like going to Ford and paying them $120/hr to look at my car. They are thieves!

 

Update: I called Ford and they assured me that an exhaust leak would not cause me that much of a fuel loss. My b/f said that maybe it could be a fuel injector leak? Any ideas will be of help, thanks guys! Also, when I wrote on my last post that my car is "jumpy", I meant that my car seems to "pause" for a few moments when I accelerate, then when it finally switches to a higher gear, it accelerates okay. Could it maybe be my fuel pressure and its expelling more gas than needed? don't get it?? Thanks!

 

If he can hear a hissing type sound in the engine bay while the motor is running then you have either a vacuum or exhaust leak. Exhaust leaks are easy to find just by sticking your head in the engine bay and smelling for exhaust fumes (of course do this in a well ventilated area, like an open-air parking lot). If you don't smell anything, then its not an exhaust leak. Vacuum leaks are a bit harder to find. Try to narrow down where the hissing is coming from by listening for the hiss. That will help determine where to go next. Here is a good video about how to find a vacuum leak:

http://www.youtube.com/user/EricTheC.../5/9CPqbaSgcok


9 times out of 10 that is true, but not always. Most autoparts stores (Kragen, Pepboys, Autozone etc) will check for any codes for free. Wouldn't hurt to have it checked. I had a friend whos car was acting weird but the check engine light never came on. I plugged my ODBII scan tool into it and there were a ton of codes. Turned out his check engine light bulb had blown, so it would have been on if the bulb wasn't bad.


That can be caused by a vacuum leak, but it can also be caused by alot of other things.


While your at it, I would also check the Mass Airflow Sensor. If its dirty or damaged it could be telling the computer that there is more air going into the motor then there really is which will cause it to pump more fuel into the motor in an attempt to even things out.

 

Pull the spark plugs and look at them. If it's running rich they'll be black and sooty(post pics if need be). When the exhaust was damaged, did the cat get damaged at all?