Check Engine light goes on and off

I have a 1997 Ford Expedition. It runs rough. Sometimes when stopped at a red light the RPM's will drop and will feel like truck is going to stall but doesn't. Other times when I first accellerate, truck will seem to get "stuck" in gear. If I let off the gas and than press the gas the acceleration will be fine. Couple of weeks ago the check engine light came on [was not blinking]. By the time I got it to the dealers the next day, the check engine light had gone off. Dealer test drove it and couldn't find anything. Dealer indicated it may be an O2 sensor but didn't want to further troubleshoot without being sure.
Couple of weeks have passed but today the check engine light came on again.
Can the check engine code be checked even after the check engine light goes out?
How extensive is replacing the O2 sensor on a '97 Expedition and how costly?
Sorry for the lack of details.
I'm worried about the severity of fixing this as I'm not in a poisition to get a new car at this time.

 

If the light came on, a code will be stored which can be retrieved at a Autozone type store for free.

It could be a O2, but check all your vacuum lines/hoses first. Look for any hoses that are cracked, missing, etc.

 

To start a blinking check engine light indicates a live missfire or skip. One bad O2 sensor wouldn't have such a drastic affect on your engine. I would start looking for vaccuum leaks and then check spark plugs and coils. Look for small cracks and burn marks.

 

The code will be stored in the car's memory until the battery's disconnected. Didn't the dealership run a diagnostic?

 

OBDII, code should be stored until reset or enough cycles occur regardless of the battery.

 

I stand corrected. Sorry

 

thank you all for the replies.

I have had all the spark plugs replaced in the past year. I've had 2 coils replaced as well. when the coils went car acted much differently than it is now.

I will check hoses and such. Will also get the codes read at Autozone and post what they find.

Thanks again.

 

Im thinking maybe an egr valve? It can cause rough idle and possible stall the vehicle. I cant remember how to check it, if i find my manual ill post it. Or someone else can tell you or give you some more possible ideas.

 

Had the code read at Autozone this morning.

OEM Number to cross: P0133
OEM Brand: OBDII

Definition
H02S-11 slow response (heated oxygen sensor Bank 1, Sensor 1)

Possible Causes:
1- oxygen sensor defective
2- fuel system running rich or lean-check other codes first

I've checked for any visible hose damage or missing hoses..none found.

Is the next common sense thing to do is to replace my O2 sensor??

 

#9 Yesterday, 10:17 AM
eb009
Member Join Date: Sep 2007
Posts: 3

Had the code read at Autozone this morning.

OEM Number to cross: P0133
OEM Brand: OBDII

Definition
H02S-11 slow response (heated oxygen sensor Bank 1, Sensor 1)

Possible Causes:
1- oxygen sensor defective
2- fuel system running rich or lean-check other codes first

I've checked for any visible hose damage or missing hoses..none found.

Is the next common sense thing to do is to replace my O2 sensor??