O2 disconnect
06-18-2011, 12:55 AM
#1
Rennlist Member
Thread Starter
O2 disconnect
Tshooting a bad idle and want to eliminate the O2 sensor.
What change would you expect by disconnecting the sensor?
'87 S4
What change would you expect by disconnecting the sensor?
'87 S4
06-18-2011, 01:24 AM
#3
Rennlist Member
Thread Starter
nope.....no difference....plugged in or not.
the idle is high when cold ~1400 eventually settles to around norm when warm but surges and sometimes stalls when driving.
TPS doesnt click so will check that through the LH but the car is untouched and original.....usual suspects under the intake me thinks.
the idle is high when cold ~1400 eventually settles to around norm when warm but surges and sometimes stalls when driving.
TPS doesnt click so will check that through the LH but the car is untouched and original.....usual suspects under the intake me thinks.
06-18-2011, 01:36 AM
#4
Nordschleife Master
On my car with O2 sensor, with the sensor unplugged the car runs fine until it warms up and goes closed loop. Then the idle hunts (low-high-low) while sitting at idle at traffic lights, intersections etc. and stumbles under acceleration.
Plug the O2 back in, restart the car, and its fine and stable.
1400 is a way high idle at cold.. usual is around 900-1k, then settling back to 675 once warmed up a little, at least on my S4's.
Plug the O2 back in, restart the car, and its fine and stable.
1400 is a way high idle at cold.. usual is around 900-1k, then settling back to 675 once warmed up a little, at least on my S4's.
06-18-2011, 01:52 AM
#6
Rennlist Member
Thread Starter
thx Hilton.....given theres no change to the idle with or without the O2 sensor Ill change it and see what changes.
Brad....Ive verified the TPS doesnt click with and without cables attached....Ill test in electrically but I believe you may just be right.....another intake job
Brad....Ive verified the TPS doesnt click with and without cables attached....Ill test in electrically but I believe you may just be right.....another intake job
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06-18-2011, 06:34 AM
#8
Rennlist Member
What happes when you unplug the O2 sensor can vary considerably.
First, you should not just unplug the sensor. The LH needs to recognise that the sensor isn't present, to force is to go into "safe mode". Disconnect battery ground, then unplug sensor. Then reconnect ground.
Then the LH detects open circuit sensor and the O2 loop is preset to the mid range of the loop. For the car to run correcty, the MAF needs to be in good calibration, as obviously the car now is running open loop.
So it is possible to get quite variable results.
First, you should not just unplug the sensor. The LH needs to recognise that the sensor isn't present, to force is to go into "safe mode". Disconnect battery ground, then unplug sensor. Then reconnect ground.
Then the LH detects open circuit sensor and the O2 loop is preset to the mid range of the loop. For the car to run correcty, the MAF needs to be in good calibration, as obviously the car now is running open loop.
So it is possible to get quite variable results.
06-18-2011, 08:46 AM
#9
Rennlist Member
Thread Starter
06-18-2011, 08:53 AM
#10
Rennlist Member
Thread Starter
What happes when you unplug the O2 sensor can vary considerably.
First, you should not just unplug the sensor. The LH needs to recognise that the sensor isn't present, to force is to go into "safe mode". Disconnect battery ground, then unplug sensor. Then reconnect ground.
Then the LH detects open circuit sensor and the O2 loop is preset to the mid range of the loop. For the car to run correcty, the MAF needs to be in good calibration, as obviously the car now is running open loop.
So it is possible to get quite variable results.
First, you should not just unplug the sensor. The LH needs to recognise that the sensor isn't present, to force is to go into "safe mode". Disconnect battery ground, then unplug sensor. Then reconnect ground.
Then the LH detects open circuit sensor and the O2 loop is preset to the mid range of the loop. For the car to run correcty, the MAF needs to be in good calibration, as obviously the car now is running open loop.
So it is possible to get quite variable results.
MAF is assummed to be OEM.
06-18-2011, 02:37 PM
#11
Three Wheelin'
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Rather than listening for the click, I would check for proper readings at the LH plug for the idle and WOT switches.
You should have continuity between pins 2 and 5 (5 is ground) at idle, and open when off idle.
Similarly, you should have continuity between 3 and 5 at WOT, and open when not at WOT.
You should have continuity between pins 2 and 5 (5 is ground) at idle, and open when off idle.
Similarly, you should have continuity between 3 and 5 at WOT, and open when not at WOT.
06-18-2011, 06:13 PM
#12
Rennlist Member
It is one way to check that O2 sensor has a problem, one would assume that if that is the case and everything is also K, then idle may well be different.
06-18-2011, 10:10 PM
#13
Rennlist Member
Thread Starter
thx John....I have a new uni O2 sensor I'll put in, reset the ecus and tshoot more.
thx SQL...this my 3rd intake R&R in a calendar year (diiferent cars), hopefully got it down now
Just call me Sean of the North 'cept we drink real beer
thx SQL...this my 3rd intake R&R in a calendar year (diiferent cars), hopefully got it down now
Just call me Sean of the North 'cept we drink real beer
06-18-2011, 11:33 PM
#14
Rennlist Member
Thread Starter
ok....spoke to soon.....the car has the original exhaust system so I have to drop the cats to onstall the O2 sensor.
I got the rear tray off and its covered in oil......rear mail seal looks like.
So.....I'll drop the cats then the inspection cover look at the rear seal and the flex plate and and and........
I got the rear tray off and its covered in oil......rear mail seal looks like.
So.....I'll drop the cats then the inspection cover look at the rear seal and the flex plate and and and........