First I started getting really bad gas mileage and had a little miss.Shortly after the SES light came on.I checked the front O2 and both looked pretty bad, so I replaced both.The SES light went away but I still only get 12 miles a gallon and I have a hesitation when Im cruisin.Im thinkin it might be the fuel filter, but I need yalls help.Can anyone think of something different it might be, I appreciate any help

 

Fuel filter probably needs to be done anyway. Try this- accelerate slowly until your converter locks up, then speed up another 5 miles an hour or so. Then roll into the throttle enough to put a decent load on the motor, but not make it unlock the converter. See if it stumbles or misses.

 

No harm in replacing the fuel filter. It will rule it out as a suspect, if nothing else.

 

I believe if you have a large enough header leak that the extra raw fuel will kinda foul up O2 sensors. Obviously they cant sense the fuel but if they are all carboned up I cant see how their ability to read O2 accurately could diminish.

 

Thanks for the responses.Tomorrow Im gonna put in a new filter and then Ill update whether it fixed it or not.

 

Radical thought.... get it scanned. Unless you've pulled power to the PCM, the code that set the SES light is probably still stored in the PCM. The PCM scan can also tell you which cylinders are missing... whether its a random patern, or one or two specific cylinders.

 

if the o2 sensors went out then most likely caused the plugs to foul out, take out a few spark plugs and look to see what kind of condition their in

 

Well I changed the fuel filter,and it seemed alot better when I first began to move, but 20 seconds later it started stumbling and it acted like it was going to die on me at stop lights.When stopped in gear, it would drop to under 700 rpms, and I dont have a SES light or anything.So Im stumped right now.

 

Im gonna use a voltometer to check the MAP sensor tomorrow, and if that checks out to be good, then I think it might be the dreaded opti.But Ill try to get it scanned at a dealership before I replace that.

 

My engine is idling pretty smooth until it gets warmed up.But if I unplug the MAP sensor, there is no change whatsoever in idle quality, could the MAP sensor be the cause of my problem.