djcummings

I have a 2000 Expedition (110,000 miles), original owner and about 4 years ago, the check engine light came on. Had it checked out at Tires Plus and they said it was indicating a problem with the O2 sensors, nothing specific. They tested each sensor and they passed. Reset the alarms, light went of but came on the next day. Have not had any engine problems until recently, have had them check test the codes, always indicates O2 sensors, test of these pass each time. This last time the code indicated a specific O2 sensor was bad. I've noticed I'm now having rough idle in cold weather, it gets better once it warms up. I've had a tune up done, new plugs a year ago so my question is, can a bad/failing O2 sensor cause this behavior or is there something else I should be looking for?

dave

Ryanp

You may have to separate issues. A slow responsive 02 sensor can cause a stumble at idle however typically when your idle problem is temperature related you may consider looking at the Idle air control valve. These typically get carbon build up on them reducing the amount of air the valve can draw in. This is a common problem with high mileage fords in the winter. If you take the valve of the engine to inspect purchase a new gasket first!

As far as your recurring check engine light with the o2 sensor I would recommend looking for and exhaust leak pre 02 sensor. This will cause in inaccurate reading thus pulling the code due to the increased oxygen reading. Last but not least I would also check your intake system for air leaks to make sure there are no air leaks after the MASS AIR FLOW sensor. I the sensor is not reading all the air the motor is drawing in this can cause a 02 light as well.

Bert

Besides what Ryanp posted, get some MAF cleaner and clean the MAF. That usually helps with the running but won't turn the light on.

__________________
Bert

djcummings

Thanks guys, I will try this and let you know!