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coolant temp sensor question

Old 08-04-2005, 09:21 AM
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Default coolant temp sensor question

i know this is kinda a hybrid question but i think it will answer my running rich problem

i have an OBD1 1992 LS converted to OBD0 in my 1991 hatch, the LS has 2 temp sensors but an OBD0 ECU only looks for one. so i asked a fwe guys and they said use the one on the t-stat housing. everything functions fine (fan, temp gauge, cold start enrichment, etc) but i run severly rich all the time and my temp gauge never reads 1/2 way.

i am thinking that i need to use teh sensor on the back of the block instead of the one i'm using now because they 2 diff sensors might have diff temp ranges they can read. am i assuming correctly?

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Old 08-04-2005, 11:21 AM
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Default Re: coolant temp sensor question


Depending on if the sensor on the thermostat housing is before or after the thermostat itself. If it's behind the thermostat, then it's going to read the about the same temp as the one on the back of the block, if it's before, then the temp will change frequently depending on if the thermostat is open or closed.

But you are correct in the fact that if your ECT doesn't reach a certain temp, then you will still be considered to be in "cold start".

..You can test this fact by setting your cold start rev limit really low (like 4000), and your hot (overall) rev limit to normal. If when this rich condition occurs, rev your car. If it stops at 4000, then you know you're in "cold start". Otherwise, you have a different issue.

...yes, this belongs in hybrid. :P
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Old 08-04-2005, 12:24 PM
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Default Re: coolant temp sensor question

there isnt any more testing needed i know i am running rich all across the map, i didnt want to try and correct it with tuning becaue i knew it was a prob when i ran teh stock ECU.

the sensor is on the "outside" if the t-stat (holy ----, its hot outside today), that would explain the occasional drop in idle when i'm sitting in traffic thats been driving me crazy.

so i guess i'll try to use the other sensor since it sounds like my assumption was correct

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Old 08-05-2005, 01:40 AM
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Default Re: coolant temp sensor question

the sensor on the T stat (OBD-1) and on the back of the block (OBD-0) would be the fan switch

AFAIK the only coolant temp sensor the ECU sees is the ECT under the dizzy on a SOHC, next to the coolant temp sensor for the gauge.

ECT need to see 168 F to fully get out of cold start, something I've been preching about for 5-6 years now.
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