O2 sensor issues
Thread Starter
Racer
Joined: Aug 2010
Posts: 349
Likes: 7
From: San Diego CA
O2 sensor issues
(2001 vert, auto, cam, UD pulley, tune, 57k miles)
I was getting wifs of sulphur when driving, and hooked up VCM scanner. Didn't spend much time on it, but noticed that bank 1 O2 sensor reading looked noisy. I had a pair of new Delco sensors and I just swapped them in. Then I got a P0300 when idling in traffic, so I took some more logs.
The O2 readings are ok when out of idle, LT fuel trims are within 5%, and the O2 swings are from 40 to 900mV. But at idle the readings get noisy, and the swings are from 300mV to 700mV. Idle fuel trims are also more negative. I also notice that the sensors are affected worse if I turn on the headlights and charging voltage drops below 13V.
To me, this looks like a ground or supply issue. How do I start checking for this?
I was getting wifs of sulphur when driving, and hooked up VCM scanner. Didn't spend much time on it, but noticed that bank 1 O2 sensor reading looked noisy. I had a pair of new Delco sensors and I just swapped them in. Then I got a P0300 when idling in traffic, so I took some more logs.
The O2 readings are ok when out of idle, LT fuel trims are within 5%, and the O2 swings are from 40 to 900mV. But at idle the readings get noisy, and the swings are from 300mV to 700mV. Idle fuel trims are also more negative. I also notice that the sensors are affected worse if I turn on the headlights and charging voltage drops below 13V.
To me, this looks like a ground or supply issue. How do I start checking for this?
Thread Starter
Racer
Joined: Aug 2010
Posts: 349
Likes: 7
From: San Diego CA
Answering for myself: I tightened the ground point below the battery, and the idle O2 swing became normal. I had been mucking with that ground point before and probably did not tighten it enough...
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
You must have your 02 voltages have an average between .400 and .550 milivolts--The highs and lows don't matter as the voltages when working properly must ocsilate between .100 and ,950--- The averages dictate whether or not the 02's are switching correctly
ALSO There are many things thgat can cause a MISIRE--IF you cannot feel or hear the misfire then it is a "false misfire"
Several things can cause a false misfire-----
1 Stall converter
2 Thinner header tubes such as shortys or LT headers
3 An underdrive pulley
4 an aftermarket cam
5 aftermarket rocker arms
In your case i suspect the underdirive pulley
The fix is to DELETE all the misfire tables in your tune by maxing out the tables--and the misfire will go away-- ALSO misfires after atime will put your timing table into the LOW OCT table where the timing can be 1/2 of normal --With an auto trans a misfire will prevent the TCC converter from locking up--as well
ALSO There are many things thgat can cause a MISIRE--IF you cannot feel or hear the misfire then it is a "false misfire"
Several things can cause a false misfire-----
1 Stall converter
2 Thinner header tubes such as shortys or LT headers
3 An underdrive pulley
4 an aftermarket cam
5 aftermarket rocker arms
In your case i suspect the underdirive pulley
The fix is to DELETE all the misfire tables in your tune by maxing out the tables--and the misfire will go away-- ALSO misfires after atime will put your timing table into the LOW OCT table where the timing can be 1/2 of normal --With an auto trans a misfire will prevent the TCC converter from locking up--as well
