Oxygen Sensor
Thread Starter
Heel & Toe
Joined: Oct 2007
Posts: 22
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Oxygen Sensor
I have an 85 automatic which seems to be relatively stock, except that a previous owner installed long tube headers. When I bought the car the driver's side header collector had a small, rusted out hole, which has gotten bigger over the last year. It is now about 2 square inches in size, and makesthe car sound like junk. I purchased new headers, and removed the corroded drivers side header. I then noticed that whoever installed the headers had installed the oxygen sensor not on the collector for that side but on the tube leading from the last (rearmost) drivers side cylinder, at least 6 inches 'upstream' from the collector. The car has been running progressively more rich and getting worse gas mileage lately. Is it possible that the leak in the collector caused the O sensor to read wrong, even though the sensor is midway up one tube? I certainly will install the senor in the new headers on the collector. Any thoughts would be appreciated. Thanks.
Pro
Joined: Dec 2009
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The o2 is probably dead from all the extra fuel the system is pumping in, but I will give you some advice about o2's and headers.
Putting them on 1 cylinder, like someone did on yours, is not good, because if the other cylinders have problems the o2 will not know and likewise if the nbr 7 cylinder(your o2) has problems, the o2 will only report that cylinder and the side as a whole.
So you need to install heated o2's, either at the reducer or at the collector so the o2 will send a better reading (all cylinders).
Putting them on 1 cylinder, like someone did on yours, is not good, because if the other cylinders have problems the o2 will not know and likewise if the nbr 7 cylinder(your o2) has problems, the o2 will only report that cylinder and the side as a whole.
So you need to install heated o2's, either at the reducer or at the collector so the o2 will send a better reading (all cylinders).
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
I would move the O2 sensor back to the reducer that attaches to the collector. Hedman makes a reducer with an O2 bung already welded in place. They are available at Summit Racing. Toss the old O2 sensor.
A heated O2 would be a good idea to replace a stock sensor. These sensors have three wires; one for the line to the sensor, another that needs 12v switched (ign) power and a ground wire. The heat provided by the electrical resistance "fools" the ECM into thinking the exhaust gasses are hot and the ECM will go into closed loop earlier.
A heated O2 would be a good idea to replace a stock sensor. These sensors have three wires; one for the line to the sensor, another that needs 12v switched (ign) power and a ground wire. The heat provided by the electrical resistance "fools" the ECM into thinking the exhaust gasses are hot and the ECM will go into closed loop earlier.
