Some O2 sensor help

[cedricmackay]

I have a 91 Explorer and I just replaced the O2 sensors because it would hesitate when you gave it gas after it had warmed up and it ran fine for a week and now it is doing the same thing again and the codes come up with a HEGO switching right error What does that mean? and is there something I can try?

Thanks in advance.

 

[cedricmackay]

Okay i was going to give a little more info since my last post.

I was given this 91 and it had the O2 sensor problem so i replace the O2 sensor and it ran fine for a week and now it is doing the same thing again I have checked the sensor like the Chilton's manual describes and it checks okay. I check the wiring harness to the computer and it checked out okay as well and i do have 12v to the O2 sensor. I did read on here that a bad ground can play havoc on things as well and i did have a bad battery clamp on the ground side so i replaced it. I still am have the same issue.

It will start up fine but when you rev the engine to 2000 RPM it starts to stutter and act like it is getting flooded and the exhaust smells rich. I also have cleaned the MAF sensor and it looked clean I am getting and error 41 still for the O2 sensor any ideas?

Thanks

 

[Bwana Bob]

Check to make sure that the fuel pressure regulator is not leaking fuel back into the vacuum line that is connected to it. Pull the vacuum line off the vacuum manifold and see if fuel dribbles out. If so, replace the fuel pressure regulator. Also, measure the fuel pressure at the schraeder valve test port on the fuel rail to make sure its not too high. Also, check the throttle position sensor.

Bob

 

[cedricmackay]

I did check the fuel regulator and no gas on the vacuum side I think it might be the TPS I wasn't getting any resistance when I put the meter on it and if I unplug it when it is running it doesn't make any difference.

 

[Glacier991]

remember the 02 sensors are messengers. Often people assume they are bad just because they give an unwanted message.

 

[rebafan]

I have a 2000 ford explorer and am having the same problem I can't afford to change all these things and find out that it is something other than what I put in. Also I can't get a reading from the computer due to a short somewhere in the wiring. I am going to sheck out what you said to check out and hopefully that is the same problem for me too. Keep the posts coming.

 

[MrShorty]

It will start up fine but when you rev the engine to 2000 RPM it starts to stutter and act like it is getting flooded and the exhaust smells rich. I also have cleaned the MAF sensor and it looked clean I am getting and error 41 still for the O2 sensor any ideas?

Assuming that 41 is a CM code. Have you recently cleared the CM codes to see if this is really a recent code and not an old code? Have you performed the KOER test (engine fully warmed up)? Do you get a 41 for the KOER test as well. It can be easier to diagnose these things from the KOER test.

The really interesting thing: you state that the engine acts like it's running really rich, but a 41 indicates to the computer lean condition. So the question is: Why the discrepancy? I'm going to think a bit, get back to us on the answers to the above questions.

EDIT: Have you checked the fuel pressure, yet??

 

[Glacier991]

[(sidebar to Cedric) Mr. Shorty is probably one of the very best engine/OBD 1 and 2 diagnosticians on this board, if he is offerring his help, follow his direction closely. He is a great resource.]

 

[ThespecialistKC]

[(sidebar to Cedric) Mr. Shorty is probably one of the very best engine/OBD 1 and 2 diagnosticians on this board, if he is offerring his help, follow his direction closely. He is a great resource.]

I wholeheartedly second the above comment.

KC