A couple of months ago my 97 with a 5.4L starting the rough idle and the check engine light came on. I kind of ignored it for a while , but lately I have started trying to fing the problem. I took my truck to auto zone to find out the codes. It read PO133 and PO1131, which I think are bother 02 sensor related. In fact the PO133 said bank 1 sensor 1. Today the truck started feeling really rough and didn't want to go and the check engine light started flashing. Can anyone help me on this.

 

behind the throttle body where it makes the 90 ...i bet it's torn

 

Thanks TexfordD I'll check the hose. Also after posting the thread I had the codes read again and I now have code #PO304 which is the #4 cylinder misfire. I looked at the coil, which I think, is the one in the rear on the passenger side for any sign of damage from water from the heater hose and found none. I still had the other two codes for the 02 sensor also. Is it possible that the 02 sensor problem have caused the Cylinder #4 misfire code or are they completely different and now I have two problems.

 

misfiring because of the lean condition...p.s. clear the codes after any repairs or they'll just continue to recycle the fault

 

I don't get it. Why is it when people get a code for O2 sensor out of range the tech or mechanic says to replace the O2 sensor?

If the bathroom scale says I'm 15 lbs overweight do I replace the scale? Or try to lose some weight. If the Doctor takes my blood pressure and its too high do I tell him"get a new sphignomonometer"?

Maybe the O2 sensor is doing it's job and signaling a problem.

Bill

 

PO131 & PO133 are both HO2 Codes.

PO131 is generally associated with a negatiive voltage reading, indicating tha the sensor's electrical connection has been contaminated with water. A coolant/heater hose is probably dripping on it.

PO133 is generally associated with an HO2 sensor that is "below some calibrated window." This basically means that it's not operating at the voltage it should be.

What you have to do now is determine why. PO133 is an upstream sensor so this is mounted on the exhaust manifold. It's not the one behind the cat.

Both of these codes can be the result of water shorting the electrical connection of the HO2 sensor, so this is what I would look for. Make sure that the coolant/heater hose is not dripping on the the HO2 sensor or the wires.

A flashing MIL is caused by an engine misfire. A permanent MIL is cause by a malfuntioning sensor or a sensor that is operating out of range for some reason. When you have a code, you need to start theorizing why.

A couple of things could be happening here. What I believe the situation to be is coolant or water dripping on the HO2 sensor (Passenger side) and causing it to short-out so that PCM thinks the engine is never reaching operating temp. What happens then is that the HO2 tells you PCM to run in open loop/rich mode.

Since this has been happening for some time, the PCM has also adjusted the fuel flow to run rich, permanently. The fuel injector has been pouring so much fuel onto the spark plug that it is either fouled and now misfiring or the injector has been pushed beyond it's limits and now needs to be replaced because it has worn out and can't flow enough fuel.

Check for water on the HO2 sensor and connections.

Many times an HO2 code is caused by a worn out HO2 sensor, but not always. They are there for a reason, so a logical, methodical approach is necessary.

MIL (s) also need to be investigated asap after they appear. Not when it's more convenient. Sensors operating out-of-range can cause major engine damage.

 

Good point AJ. A MIL indicating a bad O2 sensor reading doesn't automatically mean " replace the sensor".

It may mean there is another problem. You need an experienced mechanic or tech to track it down!

I'm no genius(or even a shadetree mechanic) but this is common sense.

Bill

 

Thanks for the valuable info. AJ, I did check the sensor for anything out-of-the-ordinary (water, loose connection, etc.), but didn't see or feel anything. I can't be absolutly sure though because I couldn't get a good angle to it because of the location. I think I'll probably go ahead and replace the sensor and put in some new plugs. At least by putting in new plugs I may also elimanate the #4 misfire. I"ve been wanting to put new plugs in anyway, now this gives me a good reason.

 

Just to let you guys know, today I replaced the 02 sensor on the front passenger side, put in 8 new Motorcraft plugs and put in a new coil pack on #4. So far everything is perfect, check engine light is off and truck is running awesome. By the way TexfordD the PVC hose and it felt fine. If I have got a leaking heater hose or water draining onto the 02 sensor I can't find them. I hope my problem is solved, at least for now.

 

Flashing check engine light is a code for a cylinder misfire, whether it is because of a fouled plug, bad wire, bad coil pack, whatever it is, it's a cylinder misfire. Been through this before, it was a headache, and it would have been REALLY bad tracking down if not for this site!