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2005 chevy trailblazer_ls
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51 Posts
Discussion Starter · #1 · (Edited)
2004 Trailblazer LS 4.2
Open/Closed Loop operation & how it affects the issues below

My first question involves the cel & how it affects mileage.I am currently in need of an oil change,which is triggering a P0014 code,cel and mileage.
For the most part,Im familiar with how open/closed loop operates.If the cel & code are being triggered by dirty oil and mileage is being affected,which of the following two scenarios will cause more consumption of fuel??
1) when the cel is on & the ecu is running in open loop mode with no o2 sensor input due to the ecu running off of preset fuel/timing values
2) when the code/cel have been cleared by the use of a scanner & the ecu is running in closed loop mode with o2 sensor input,but with the vvt solenoid likely causing over advanced timing until it goes on long enough (1 day of driving) before the code/cel get triggered again.
BTW- I'll be doing an oil change in two or three days when my schedule allows it & I know 100% for a fact that this code is indeed being caused by dirty oil
So Im trying to deduct,for the purpose of fuel mileage (until I can get to doing the oil change) whether it would be better for me to clear the code/cel or just leave them on til the oil change is done?? IOW - which of the 2 scenarios listed above will burn less fuel??


A second issue is related to the thermostat and ect sensor.Im aware that some vehicles use a sender for the temp gauge and a ect sensor for the ecu while others,like the Trailblazer,use a ect sensor for both functions.I know its time to replace the ect sensor and thermostat on my TB because of the fuel consumption thats been occurring & the fact that my scanner is reading 33°F for the ect sensor after the engine runs for 20+ minutes plus a code/cel comes on after weeks of driving.My curiosity is related to the gauge.How is it that if the gauge and/or ecu uses input from the ect sensor for the gauge reading,the gauge is reading the correct 210° temp while a scanner is only showing 33°?? The ecu,gauge & scanner are all using the input from the ect sensor,correct?? If so,I dont see how this is possible.Now about the thermostat.If the tstat is stuck open,the coolant temp will still reach a temp way above 33°,correct because I checked it at the end of summer also and not just days ago when the ambient temp was 40° here in Nashville,but of course that reading is from a scanner thats using the ect sensor for its reference.:unsure:
BTW - Im assuming the tstat is stuck open.Im also aware that the ecu is supposed to richen the fuel trim at cold start and lean it out once the engine warms up.After the engine reaches operating temp or as close as it can get with the tstat stuck open plus the ect sensor outputting a 33° temp reading,it seems like the ecu would be richening the fuel trim so much (since it believes the coolant temp is at 33° on a warmed up engine) that it would prevent you from being able to start the engine (at operating temp) without flooring the gas pedal during crank/start mode to cutoff injector pulse long enough to clear any excess fuel to allow engine startup,but my TB (knock on wood) starts every time with no issue,it just runs rich and burns excess fuel.Any additional fuel thats being added due to the faulty ect sensor and tstat(??) hasnt yet triggered any pre or aft cat o2 sensor codes either,so that seems like the cats haven't been affected negatively (knock on wood) as of yet.So with the info posted above,can anyone explain these situations
Any help is appreciated.....
 

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Registered
2005 chevy trailblazer_ls
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51 Posts
Discussion Starter · #2 ·
Wow no replies yet.Im more of a Mustang Guru & dont know the ins/outs of the Trailblazer yet,but theres usually a guru or two on most model specific forums.Maybe someone will chime in later.
 
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