o2 not switching/running lean

[2ndgen]

i pulled koeo codes and it says o2 not switching / running lean i cleared the code. next drive it came on again i pulled the o2 sensor and it was black as could be, took it in to parts store and they say its running rich because of the color. as it was a new o2 still under warrenty i got another new one put it in cleared codes and same thing CEL came on and got the same message running lean/ o2 not switching????

how can the code say running lean but the sensor look like its running rich?
and what would cause it not to switch ever?

the CEL only comes on after about 20 min of driving.


any thoughts??

 

[Psychopete]

any thoughts??

You can't necessarily trust that the code in question is actually a sign of a bad sensor - also keep in mind something else could be contributing to the problem causing the sensor to read values that are not normal.

The engine probably has been running rich as a result of the oxygen sensor sensing too much oxygen in the exhaust, and it is trying to compensate.

One of the most common causes for this code is a vacuum leak. Could be a few other things, any "lack of fuel" condition, but vacuum leak is most common IMO. Basically the oxygen sensor is sensing oxygen levels in the exhaust that are higher than normal.

 

[2ndgen]

You can't necessarily trust that the code in question is actually a sign of a bad sensor - also keep in mind something else could be contributing to the problem causing the sensor to read values that are not normal.

The engine probably has been running rich as a result of the oxygen sensor sensing too much oxygen in the exhaust, and it is trying to compensate.

One of the most common causes for this code is a vacuum leak. Could be a few other things, any "lack of fuel" condition, but vacuum leak is most common IMO. Basically the oxygen sensor is sensing oxygen levels in the exhaust that are higher than normal.

i have replaced all the vacuum hoses but can still feel/hear a leak some where iv sprayed all around the hoses and gaskets with wd40 but cant seem to locate what little leak is there, some where?
the truck also goes through gas like a pig im only getting 13 MPG im thinking the injectors have a bad seal iv had them cleaned and have tested all the injectors they all read .014 and spec says between .012-.018
and i had a hole right where the exaust pipe and the muffler meet i seald it with quick still.
all the issues: lifter tick, gutlessness, rad leak, so on and so on i could deal with much better if i could get the gas issue resolved.
but the sensor problem is starting to piss me off the CEL light is like clock work i can tell just about the same point every drive when it is going to come on.

 

[kimcrwbr1]

Take a piece of vacuum hose about 3 feet and hold one end up to your ear and go around to all the gaskets fittings and hoses and listen for the hiss. If you put the end in the TB when it is running you will know what to listen for you can pinpoint leaks that way also. For hard to get at areas tape it to a soft wire like a clothes hanger or copper wire to reach tite places you can find exhaust leaks like that also. Just be careful of moving parts. Run a vacuum guage and do a compression test will tell you what is going on inside the engine. How many miles are on the engine and are you losing oil but not dripping could be valve guide seals how do the plugs look.

 

[2ndgen]

Take a piece of vacuum hose about 3 feet and hold one end up to your ear and go around to all the gaskets fittings and hoses and listen for the hiss. If you put the end in the TB when it is running you will know what to listen for you can pinpoint leaks that way also. For hard to get at areas tape it to a soft wire like a clothes hanger or copper wire to reach tite places you can find exhaust leaks like that also. Just be careful of moving parts. Run a vacuum guage and do a compression test will tell you what is going on inside the engine. How many miles are on the engine and are you losing oil but not dripping could be valve guide seals how do the plugs look.

76xxx showing it only goes up to 100xxx then resets, i havent noticed any oil loss since i redid the valve gaskets, and i did a full tune up 3500 miles ago when i got the truck but the plugs i pulled out where as the o2 sensor black as night... ill try the hose trick though.

 

[kimcrwbr1]

Yea it is the only way I look for vacuum leaks any more. Did you change the PCV valve I buy the good ones and change it with spark plugs they are cheap and there is no way to clean it properly I just do it with tune ups it can be a bad vacuum leak or plug up and you get oil all over the engine or blow a seal or gasket. If you have alot of blow by with a new PCV you can get one for a V-8 to pull a little more out of the crankcase without affecting vacuum much.

 

[Psychopete]

Is the hiss coming from the brake booster area?

 

[kimcrwbr1]

I checked my book I am guessing you get a code 41 it says
improper fuel delivery check fuel pressure and injectors
vacuum leaks
EGO sensor done that
wiring harness and connectors
ECA problems
Once you get the code to go away pull about 1/4 a can of seafoam in the vacuum line going to the vapor cannister when the engine is hot and shut it down immediately let it set for about ten minutes and pour the rest in the tank. Start it and run it about 3000 rpm until the smoke show goes away preferably up wind of the neighbor you dont like. Then I like to chase it with about a cup of water to dissolve any carbon it may have missed you will have to rev it up while your sucking the fluid in so it dont die. Neither one will harm your cat/s. I am voting for the PCV valve it is the cheapest part to replace and a new throttle body gasket couldnt hurt either.

 

[kimcrwbr1]

Does the engine rpm change when you depress the brakes

 

[kimcrwbr1]

hopefully it is just the rubber grommet for the fitting

 

[kimcrwbr1]

A little RTV black overnite will fix that temporary till you get a good one

 

[kimcrwbr1]

Is the hiss coming from the brake booster area?

Sorry Pete I thought you were the other guy saying it was coming from the booster

 

[2ndgen]

yes the break booster hisses only when the hose is bumped not all the time.


yes when break is depressed the rpms change.


yes i changed the pvc valve and the little rubber gromet on/in th evalve cover, also the big plastic thing on the other valve cover and its rubber gromet.

 

[kimcrwbr1]

Check inside the cab where the actuator rod for the brake goes thru the firewall with the vacuum hose while the engine is running you should only hear it suck when the pedal is depressed. You should be able to press the brake twice after the engine dies and still have the vacuum assist. Let us know either way what you find out. If you can get your hands on a vacuum guage hook it up on the manifold with the FPR you should be getting 17-20 hg at an idle and 20-21 at 3000 rpm. There is a section in the tech library for reading the vacuum guage.

 

[kimcrwbr1]

I forgot when you put in the new 0-2 sensor did you reset the computer by disconnecting the battery for about 1/2 an hour. First clear the memory then disconnect the battery for at least 15 mins it could be still running on old values the computer adjust for normal wear but wont go backwards. Reset the computer and run it at medium speed for 15 to 20 mins to set the new values and retest when the engine is still hot.