MY EXPY WONT STAY ON

OK EXPERTS PLEASE HELP ME
MY TRUCK WILL START BUT WONT STAY ON, ABOUT SIX MONTHS AGO MY CHECK ENGINE LIGHT CAME ON THE COMPUTER TOLD ME ONE OF THE OXYGEN SENSORS WAS BAD WHICH ONE? DONT KNOW I THINK IT HAS FOUR. TRUCK WAS RUNNING OK UNTIL LAST MONTH TRUCK WILL STAR BUT WON'T STAY ON AS SOON AS I TAKE MY FOOT OF THE GAS PEDAL IT SHOTS OFF......WILL APRECIATE ANY INFO ON IT.

ok. the expeditions computer sucks in that it wont tell you which sensor is bad but you can just try the process of elimination. buy one O2 sensor for abought $60 and replace them one at a time checking if the vehicle works after replacing one. if it doesnt put the old one back in and try another. it sounds to me that that might be the problem. i had this problem except my vehicle never shut off. well good luck

We are having the same problem with our 97 Expedition, we have replaced the 02 sensor and all the spark plugs...sometimes the Check Engine light comes on, sometimes it doesn't....I hate to sound stupid, but are there other 02 sensors on this thing?

thanks for the help

Have a 2000 expy EB. Same problem the other day. turned out to be the Idle air control valve. Now I think we have a transmission problem. It skips going down highway, almost dies going uphill unless I really step on it. No change in engine rpms when it does this. Any Ideas?

Yes it is the Idle Air Contol Valve. Replaced mine 2 days ago only takes about 10 minutes

daniel

Most oxygen sensor fault trips are caused by other things. Occasionally, they will fail. The most common code to trip is the "lean O2" code. This can be caused by any number of problems from leaking PVC hose, vaccum leak, leaking EGR hoses, leaking hoses to the IAC valve, and the IAC or Idle Air Control Valve amoung other items. Subsequently, I had problems in all areas with my 1997 Expedition. The IAC valve is located at the rear of the intake manifold, near the firewall. Your intake will have two each hoses just before the throttle body, these hoses bypass the throttle body and go directly to the IAC valve (you can follow the lines with your hands to the IAC valve). This valve is directly controlled by the engine managment computer, and adjusts to maintain the desired idle. The intake air still enters through the air filter, passes the mass airflow sensor and intake air temp sensor. Depending on the year and month of manufacturer, your IAC valve part number may be different. If you replace it, I would remove it and ensure the replacement part number matches the part number of your existing part.

The valve is only about $45, but you should check all the hoses and lines before jumping to replacing the IAC valve.

Again, this isn't to say that O2 sensors don't fail, but they may be working properly and sensing a valid lean operating condition.

Good luck.

I had a similiar problem a few months ago. It turned out to be the mass airflow sensor located between the air cleaner and the throttle body. If you open the air intake near the air cleaner and look in the tube going towards the engine, the sensor is on the bottom. it looks like a square with a wire on it. Mine had a piece of crud on it. I carefully removed the crud and sprayed carb cleaner on it, the problem left and never came back. If you are getting codes saying left bank and right bank are both lean, it indicates that you have a vacuum leak. The odds of 4 o2 sensorsw going out at the same time is small.

HELLO FRIENDS SORRY I BEEN OUT FOR A WHILE....
YES IT WAS THE "IAC valve" IT WAS LIKE $80
IT TOOK ME 20 MIN TO REPLACE. BUT THE CHECK ENGINE LIGHT STILL ON SHOULD I TAKE IT TO THE COMPUTER PLACE AND GET THE CODE......I HAVE TWO 02 SENSORS SOME PEOPLE TELL ME TO REPLECE ALL OF THEM BUT OTHER PEOLE TELL ME NOT ALL GO BAD AT THE SAME TIME..HELP AGAIN EXPERTS......IM GOING TO CHECK FOR ANY LEAKS FIRST ..............

[honezk9]

The reason your check engine light is on may be because the code is stored in memory. You need to tell the computer to reset the check engine light, this will turn the light off until the computer senses another failure event. You can reset your check engine light a number of ways: 1. Buy a carchip, you can get the carchip at sears or other places, they are about $100, it fits in the com port below the steering column. You can leave the carchip plugged in while you drive, and when the check engine light comes on, you remove the chip and connect it to your home computer. The carchip will let you know what code(s) are the problem. This definately helps in diagnostics and can prevent you from buying parts you dont need. When you connect it to your computer you can "clear" the check engine light, thus, when you plug it in to you expo, the light will go out. 2. method number 2 is cheaper. disconnect the battery.