88 renix o2 heater
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
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Joined: May 2008
Posts: 3,018
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Year: 1988
Model: Cherokee
Engine: AMC242
The HEGO heater relay is there to eneregize the heater element in the HEGO tip, which is usually done for a bit after a cold start. The timing is set by the ECU.
Why? Because an exhaust gas oxygen (EGO) sensor won't generate a reliable signal until it reaches some 700-750*C. The first-generation one-wire units relied upon exhaust gas temperature to get the sensor tip up to op temp - which took anywhere between five and ten minutes.
They rapidly became "HEGO" (Heated EGO) sensors (two-wire or three-wire, depending on application,) because adding a heating element knocked that warmup time down to about 30-45 seconds, which meant that closed loop fuel control could kick in that much faster. This not only reduced emissions, but usually has the nice side effect of measurably better fuel economy.
Why? Because an exhaust gas oxygen (EGO) sensor won't generate a reliable signal until it reaches some 700-750*C. The first-generation one-wire units relied upon exhaust gas temperature to get the sensor tip up to op temp - which took anywhere between five and ten minutes.
They rapidly became "HEGO" (Heated EGO) sensors (two-wire or three-wire, depending on application,) because adding a heating element knocked that warmup time down to about 30-45 seconds, which meant that closed loop fuel control could kick in that much faster. This not only reduced emissions, but usually has the nice side effect of measurably better fuel economy.
Another piece of the puzzle! Thanks 5-90.
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Joined: Dec 2011
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Model: Cherokee
gone threw most of your items. waiting on a hb to check dizzy timing.
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Thread Starter
Junior Member
Joined: Dec 2011
Posts: 40
Likes: 0
Model: Cherokee
The HEGO heater relay is there to eneregize the heater element in the HEGO tip, which is usually done for a bit after a cold start. The timing is set by the ECU.
Why? Because an exhaust gas oxygen (EGO) sensor won't generate a reliable signal until it reaches some 700-750*C. The first-generation one-wire units relied upon exhaust gas temperature to get the sensor tip up to op temp - which took anywhere between five and ten minutes.
They rapidly became "HEGO" (Heated EGO) sensors (two-wire or three-wire, depending on application,) because adding a heating element knocked that warmup time down to about 30-45 seconds, which meant that closed loop fuel control could kick in that much faster. This not only reduced emissions, but usually has the nice side effect of measurably better fuel economy.
Why? Because an exhaust gas oxygen (EGO) sensor won't generate a reliable signal until it reaches some 700-750*C. The first-generation one-wire units relied upon exhaust gas temperature to get the sensor tip up to op temp - which took anywhere between five and ten minutes.
They rapidly became "HEGO" (Heated EGO) sensors (two-wire or three-wire, depending on application,) because adding a heating element knocked that warmup time down to about 30-45 seconds, which meant that closed loop fuel control could kick in that much faster. This not only reduced emissions, but usually has the nice side effect of measurably better fuel economy.
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Joined: May 2008
Posts: 3,018
Likes: 23
Year: 1988
Model: Cherokee
Engine: AMC242
Our big focus there is RE of the RENIX system to figure out how it works (one of our pet projects right now is decoding the data stream,) and the group is fully moderated - so be sure to let us know why you're there (or you'll be rejected out of hand.) I got tired of SPAM years ago - I have about four "assistant listmoms" there, so we tend to get things handled relatively quickly.
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