diagnostic code help and other ?????

[ducksplus]

ok i performed the koeo and koer test tonight and i got the following codes..
koeo... 11.. i know is system pass
cm... 41.. HEGO sensor circuit indicates system lean (right side)... what does that mean???
koer... 11.. system pass

What does the CM code 41 mean???

Another ??
I have a continous click in my gas line running up to the engine.. i pin pointed it by a screwdrive to the ear trick..
What could be causing this???
My EX is getting 10 mpg..... 200 miles per tank... this is my reason for trying to find out whats wrong....

Last ??... I noticed tonight when the engine was at idle that my spark plugs really glow... and when i rev it up they are like flashlights??? i figure a little glow does the glow indicate bad wires??? i just changed the plugs but not the wires...
IF ANYONE CAN HELP WITH THIS GAS DRINKIN PROBLEM I WOULD BE REALLY GREATFUL!!!!
Thanks

Mike

 

[ducksplus]

forgot to say..

my check engine light comes on about 10 minutes after i start driving...
and sometimes it goes off... but comes back on..
any help please..
mike

 

[Runnin'OnEmpty]

Mike, code 41 is "O2 sensor voltage signal always lean (low value) - does not suitch. This code indicates a bad O2 sensor, because of no switching. I'd replace it. This will help improve the poor mileage.

The clicking might just be noise from an injector. They click while opening and closing.

Last but not least, the glow or arcing from the plugs indicates high resistance in the plug wires. I'd also replace them. Also clean the ceramic tops of the plugs. Use a paper towel with a little alcohol. When installing the new wires, apply a dab of dielectric grease in the boot.

Good luck,
ROE

 

[MrShorty]

In the absence of a CM41, I would half suspect a KOER 41 as being operator error. A false KOER 41 is easily set by performing the KOER test without preheating the O2 sensor. I would repeat the KEOR test, making sure to run the engine for a few minutes immediately before setting up and running the KOER test.

A continuous click in the gas line running up to the engine? Does it correspond to the click of the fuel injectors? That would be my first guess.

As ROE indicated, it sounds like you need new plug wires.

 

[ducksplus]

with the cm 41 error, do you think its just the 02 sensor?? should i replace that and see?
ill rerun the koer test tonight wth the engine good and warm..

 

[MrShorty]

Based solely on a trouble code, I would never assume the O2 sensor is bad. There are a lot of possible causes of a KOER41/CM41. One possibility: Excessive misfires could trigger O2 sensor lean codes. Based on your description of the plug wires, I could easily envision that engine misfiring. My advice would be to fix what is known to be broken (the plug wires), and see where that leads.

 

[ducksplus]

thanks.. ill start there.

mike

 

[ducksplus]

ok i came home this afternoon and reran the test after the engine was warm...

koeo... 11
CM......41, HEGO sensor circuit indicates system lean (right side)
koer....42, NO HEGO switching detected always rich (right side)

Now can you help me more since i have these two codes...
Mike

 

[Runnin'OnEmpty]

Posted by:Runnin'OnEmpty

Mike, code 41 is "O2 sensor voltage signal always lean (low value) - does not switch. This code indicates a bad O2 sensor, because of no switching. I'd replace it. This will help improve the poor mileage.

Mike, it's a bad O2 sensor, in my opinion. The no switching plus the bad mpg points to the sensor.

 

[ducksplus]

ok so my next question is where is the o2 sensor located on the 91 xlt...
i have been told there is only one..
where is it...
thanks
mike

 

[MrShorty]

Interesting contradiction: CM 41 indicates that at some point in the past the O2 sensor indicated always lean, the KOER 42 indicates that the O2 sensor always showed rich during the KOER test. Sometimes with O2 sensor codes (especially if the sensor is old) it can make sense to replace the sensor and then do the full diagnosis if the codes don't go away with the new sensor.
Have you replaced the plug wires, yet? If so, did you clear the CM code before repeating the tests?

 

[ducksplus]

no i havent replaced them yet... im going to try to do it this weekend... and im probally going to pick up an o2 sensor too.. the guy i bought the truck from bought it new and he said he never replaced the o2 sensor.. so im going to do both and see what happens then...

 

[MrShorty]

ok so my next question is where is the o2 sensor located on the 91 xlt...
i have been told there is only one..
where is it...
thanks
mike

There is only one and it is in the junction of the Y pipe just upstream of the cat.

 

[ducksplus]

is the o2 sensor hard to change... because i read somewhere that i can be done wrong if you dont know how??
MIke

 

[aldive]

is the o2 sensor hard to change... because i read somewhere that i can be done wrong if you dont know how??
MIke

Sometimes ( most of the time ), they can be a ***** to get off; other thyan that. nothing to it.

 

[Rhett]

is the o2 sensor hard to change... because i read somewhere that i can be done wrong if you dont know how??
MIke

I'd change the plug wires for sure, and proibably the plugs too since you'll be in there anyway and spark plugs are cheap. And if the O2 has never been changed...well, that's been in there since 1991 (really 1990, when the truck was built) and so it's no surprise if the O2 is bad as well.

O2's can be very difficult to get out, especially one that's been on there for 15 years. You will most likely need what is called an, "O2 Sensor Socket". It's a special socket with an open side so that the socket fits over the wire attached to the O2S.

You can't "do it wrong"...either the O2 comes out or it doesn't...unless you cross-thread the new O2...that would be bad.

 

[ducksplus]

can the o2 sensor be changed without the special socket??? How do you usually take yours out???
mike

 

[Runnin'OnEmpty]

A 7/8" open end wrench will fit as well. Place the wrench on the sensor, and tap the wrench end lightly with a hammer. The hammer vibrations should work it loose. They're not too hard to get out, IF they're easily accessable. Your's, since it's in the Y-pipe, should be relatively easy to get to......

 

[Rhett]

can the o2 sensor be changed without the special socket??? How do you usually take yours out???
mike

I use the special socket. But as ROE said you can use an open ended wrench too. I've done it both ways.

You may have trouble removing that 15 year old sensor, and if so try soaking it with PB Blaster or some other quality penetrant. If you have room, you can also use a cheater (slip a pipe over your wrench to get more length and leverage). Sometimes it helps to jack the truck up a little or drive it up on ramps so you can get more shoulder into your wrench.

 

[ducksplus]

ok i changed the o2 sensor tonight.. i took it for a spin and my check engine still came on about 15 minutes of driving... i got back to the house and ran my test again and still
koeo..11
cm...41
koer....42
What should i do next???
mike