Jarren_b

I have a PLX wideband that ive put about 20k on since I got it..

The strange thing is its been dead on until yesterday

I drove to work yesterday and it was dead on.. Drove home and it was reading 11.7 at WOT!! Im usually 12.8 or so..

Would the sensor going bad cause it to show a full point rich?

My car seems to be running fine and I havent changed anything recently..

I recently got launch control in my car, could all the unburned fuel from the launch control being active ruin the sensor?

At cruise and idle the sensor seems to be running the same as it always has..

Im lost at this guys, what do you think??

jimmyblue

iTrader: (11)

The fail mode I've seen is, reading gets jacked way lean.
Not to say there couldn't be others.

Sure you've got things like COT turned off? There are
some fueling modes that will override the normal AFR.

Sensor doesn't read fuel, it reads oxygen and does
some hokey math to get an AFR or EQ number from
that.

Knowing what the commanded AFR at the time was,
and how commanded usually relates to delivered, would
be useful.

Moore Racecraft

I've seen thermal shock take em out pretty quick. Raw fuel or coolant will do it pretty quick. Does it free air cal?

danieloneil01

Can this unit be calibrated?


Got any CELs? Got a way to log the car?

Blown06

iTrader: (32)

I know that on the AEM uego widebands, when the sensor goes bad, the gauge will just read a constant number and never change.

Jarren_b

I feel like an idiot guys. I did a free air test and it passed with flying colors (my unit is self calibrating) While I was poking around my motor trying to find the problem I noticed my intake boot before the maf was loose so I pulled it apart and found a piece of electrical tape stuck to my maf. I feel like my car gained 30 hp lol.. Runs great and now my gauge is dead on again!

Moore Racecraft

Glad to hear it worked out....

Rise of the Phoenix

iTrader: (27)

Glad you got it figured out. I do have a question though. Would a loose wideband sensor that I have screwed into the bung port cause lean readings? I've been having really bad lean readings, especially at idle and cruising speeds. Last night I checked were I have the sensor screwed into the bung and it was way loose. Would that cause lean readings?

Jarren_b

I would think that it very well could.. I wonder if there is some kind of vacuum in the exhaust at cruise causing it to suck in outside air.. just an idea but being that the leak is at the sensor itself I would definitely say it could.. I know that my wideband reads about .2 too lean all the time because my sensor is in one of my rear o2 bungs that I wasnt using..

Rise of the Phoenix

iTrader: (27)

I didn't realize it was loose till late last night, so I haven't had a chance to fire it up and see if the idle AFR is any different than it was last week. It was running stupid lean at 75 mph cruising on the highway. I'm talking like between 17 and 18, and if I put it in 6th gear, it would go so lean that it wouldn't register on the gauge. When I get on the car hard, air/fuel drops, but it's still in the 14.5 range, which isn't too safe. I'm hoping it was all due to the sensor not being screwed in tight.

Jarren_b

Yeah I mean if your car seems to be running ok still then it must be something with the wideband.. Mine was surging like crazy when that piece of tape was stuck on the maf so if yours isnt doing anything out of the ordinary I would bet it was cause it was loose

Rise of the Phoenix

iTrader: (27)

Only surging it does is in 1st gear when you're not giving it too much gas. Other than that, it drives great.

Rise of the Phoenix

iTrader: (27)

Well, It didn't help. Still running super lean while cruising around. 1st, 2nd, 3rd, 4th, 5th, and 6th under partial throttle it's in the 16 to 18 range. Thought the loose sensor was the cause, but guess not.

soundengineer

iTrader: (16)

there is an easy test for a wideband o2 sensor


take the thing out, turn on your wideband....
it should read free air(or its highest value)

then take a rag, and spray some brake cleaner in it...
wrap it around the o2 sensor
the AFR should creep richer and richer....(it should stay rich until all the brake cleaner evaporates)
if at some point it suddenly shoots up to free air again, then the sensor is toast

if it stays rich, then it is ok.

its a well proven test, and you can see it on videos on youtube if you need to see it visually to verify your results

Rise of the Phoenix

iTrader: (27)

A rag with gas will work too, right?

soundengineer

iTrader: (16)

no idea... I've only done it with brake cleaner

Rise of the Phoenix

iTrader: (27)

Thanks. Gas should work too, as too much fuel is what causes the rich readings on a wideband. I'm pretty sure the wideband is functioning fine, but doesn't hurt to rule it out.

soundengineer

iTrader: (16)

Actually...Fuel has nothing to do with it....
it reads oxygen content, not fuel content
I'm not certain a rag with gasoline would work....the combustion process is what breaks down the gasoline to allow the O2 sensor to detect left over oxygen
the brake cleaner breaks down immediately upon contact with the air and the sensor can see the left over oxygen

Rise of the Phoenix

iTrader: (27)

Makes sense. Thanks for explaining it to me. I will use the brake cleaner and test that way. I appreciate the help.

joecar

The brake-cleaner-rag test: the evaporating brake cleaner displaces any air (oxygen) in between the rag and the wideband sensor, this causes the wideband to show rich (the brake cleaner does not ignite, it evaporates).

Gasoline does the same thing, except it does not evaporate as quickly as brake cleaner... but be careful, gasoline vapor ignites very easily, don't get burned.