I've been trying to track down a check engine light issue..

94 mercury villanger 3.0 v6 OBDI

Recently gave the car a tune up.. needed one bad. (plugs,wires,cap,rotor,fuel filter,pcv valve, air filter)

However when going up a hill (some loss of power), the check engine light illuminates and goes away shortly after..

It however has a Stored code 33... meaning heated o2 sensor error. But according to the manual it does not illuminate the dash... its only a stored code...

I can never get somewhere to check the code in time when it does come up.


Suggestions for things to look at?

regarding code 33? os2 sensor bad? what can cause it to trip?

Thank you

Went out and looked at the new spark plugs.. they have about 100 miles on them and they are as white as they were when they came out of the box.. it also has a slight off idle stumble.. suggestions beside o2 sensor? i have one on order

Maybe a vacuum leak or a bad fuel pump/filter. The CEL may be coming on because it's trying to stall?

it doesnt want to stall.. it just loses all power.. the spark plugs are snow white... code 33 is in the computer.. has a slight off idle stumble.. Already did a full tune up and changed filter.

it doesnt want to stall.. it just loses all power.. the spark plugs are snow white... code 33 is in the computer.. has a slight off idle stumble.. Already did a full tune up and changed filter.

Sorry, when I said stall I meant what the computer sees and not what you feel. When it looses power you are also changing the way some sensors see vacuum, this could cause the CEL light to flicker on. Not all problems will generate a code and/or CEL. The plugs being white can also indicate a lean condition. Check your MAP/MAF sensor and it may be time for a fuel pump pressure/volume test. Also check the wiring to the 02 sensor/s to make sure that it is not rubbing on something and causing an intermittent short. O2 sensors should be replaced every 100K.

what should the fuel pressure be? can a bad tps cause this?

Replace the sensor. It will cost less than all the tunel up parts and it is what it indicates you need. You have this problem when your car needs power and the O2 reads heat and exhuast vapors to determin the required fuel and air to mix to get you up the hill. If you want you can check the EGR hose and part by just reaching around it and push it up from the bottom it should stall the car and if you have a leak you will be able to tell as well

I havent had time to work on it, if i unplug the oxygen sensor, it runs worse with a bad off idle stumble, a symptom of tps?