I'm going to ask a dumb question but first some background. My 97 F150 with 5.4 has been running a little rough at times. Sometimes only slightly rough at idle and sometimes very rough. Once in a while when I'm accelerating it runs so rough that it feels like it is only running on 5 or 6 cylinders . I have 78000 miles and the plugs were changed, injectors cleaned and 1 coil pack replaced at 62000 miles. Also check engine light is on and code says that the O2 sensor on bank 1 front is responding slowly. This sensor has been replaced twice but after about 25 or 30 miles CEL comes back on and symptoms start all over. Any solutions are welcome. Also there are no misfire codes. My dumb question is this Which side of the engine is bank 1? I have been told by different people both sides. Which is correct?

 

Bank "1" is always the side of the engine with cylinder #1.

An O2 sensor responding slowly usually means that it is worn out and no longer reading accurately. At 78,000 miles it is perfectly normal to have to replace one or all O2 sensors.

Bank 1, front O2 sensor would be on the exhaust manifold, passenger side of the engine. Did you happen to notice if coolant is dripping onto the O2 sensor or #4 coil (at the back, passenger side), from a leaking heater hose???

Has the fuel filter been replaced???

 

Yes the fuel filter has been replaced. The reason I asked has been answered now. The guy at Auto Zone that did the scan told me that bank 1 was the drivers sude which would explain why changing the sensor didn't help. Also I have not noticed any drips or leaks but I will check more closely. Now the next question is how do you get to the sensor on the passenger side? That little sucker is tucked up in there in a really tight spot. Any suggestions?

 

Might want to check one other thing. I have a 1998 F150 5.4L and had the same problem, and was told by the people at PEP BOYS that the O2 sensors were bad and at 78k they probably were. However, the reason that my truck was running rough was that the rubber boot from the PCV valve had broken off from the back of the intake manifold. I didn't find it until 3 O2 sensors and a complete plug change later.

Steve

 

I have almost 100k on my 99 5.4. It seems to idle ok, but when I get in the 2000 rpm range it will miss sometimes. Sometimes really bad others, not so bad. Then there are times with no miss at all. I did blow out a plug a couple of weeks ago and repaired it with a helicoil. Does anyone have a suggestion on what to try?

I put a can of sea foam in to try to clean the injectors and EGR. I will change out the fuel filter this week. What code should I be sending (on the little odometer trick)? No "check engine" light is on.

I'm just getting a little gunshy. The week after doing the helicoil I put 1500 miles on in 4 days with about 16-17 mpg at 75 mph in the mountains.

I put the sea foam in to try to clear up some pinging I got when I was accellerating up a couple mountains at about 70.

Any help is appreciated.