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Location:
Sydney
Registered:
January 2004
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Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 01:25
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Trying to solve fuel economy problem.
4AFE Automatic in AE92
So far replaced air filter, fuel filter, oil, coolant etc. Thermostat as well as it was stuck open.
The car is using high 10s-11L/100km. So about 32L for 300kms. Compared to my 4AGE this is woeful. Considering it was mainly cruising at 70km/h driving. I know autos use a bit more but I think my parents 626 auto (2.0) would be a fair bit better. Than this
Do oxygen sensors make much of a difference to fuel economy? I heard that they only trim a little fuel? I guess if they trim 10-15% that would get the fuel consumption down to respectable figures.
Would this be the next point of call? The 02 sensor?
Car runs really well just using a bit too much fuel I think.
With the new thermostat - warms up in about 4-5 mins and temp stays on 1/2 the whole time. Is there a seperate temp sender for the dashboard mounted intrument than the one to the ECU whichhelps decide the mixture?
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 01:44
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Holy shit, that uses as much if not more than my 21R-C RA60! Oxygen sensor can play a big part in fuel economy, I'd be getting it looked at and/or replaced.
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Location:
Brisbane
Registered:
February 2003
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 02:14
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| HighRolla wrote on Mon, 10 January 2005 11:25 |
Trying to solve fuel economy problem.
4AFE Automatic in AE92
<BIG SNIP>
With the new thermostat - warms up in about 4-5 mins and temp stays on 1/2 the whole time. Is there a seperate temp sender for the dashboard mounted intrument than the one to the ECU whichhelps decide the mixture?
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yes, there is invariably one sensor for the ECU and another for the dash.
O2 would only affect fuel use at idle or cruise
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Location:
Sydney
Registered:
January 2004
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 02:55
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So are you saying it won't make much difference chuckster?
the feed back is always being used during closed loop right (the 02 sensor that is)? It is only open loop when you nearly full throttle it that it isnt going to effect anything?
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Location:
Brisbane
Registered:
February 2003
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 03:33
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depends on how and where you drive - a heavy load or lots of accel or decell (e.g. a hilly, winding suburb) will not engage close loop at all - until you come to a halt in the driveway - hwy driving and peak-hour traffic it will make significant difference.
It's not just WoT that enables open loop in an ECU - closed loop only comes on in a narrow band of revs/load (unless your ECU supports variable AFR targets across the fuel maps and that's only likely in a very new car, an expensive aftermarket ECU or Megasquirt II)
as we don't know what the code does in the toyota ECUs we can only guess as to how much correction the ECU will apply to it's base fuel map - most factory setups will err on the side of caution (not too lean to prevent engine damage) and will force emission standards only when needed.
can you get the ECU to spit out any error codes? rich fuel use could also come from an air leak, faulty air or water temp sensors, etc.
then there's the automatic gearbox - is it slipping more than usual? is the fluid newish and has any bands/brakes inside it been adjusted/serviced properely?
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Location:
Sydney
Registered:
January 2004
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Location:
Brisbane
Registered:
February 2003
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 04:22
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coolant temp sensor should be in thermostat housing along with the dash sensor and the cold start time/switch (if the engine has cold start.
i not know too much about 4afe - sorry.
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Location:
Sydney
Registered:
January 2004
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Location:
Sydney
Registered:
January 2004
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Location:
Sydney
Registered:
January 2004
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Location:
Sydney
Registered:
January 2004
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Mon, 10 January 2005 22:28
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Spoke to a decent mechanic. He reckons that fuel economy is ok! I don't think so. 220k kms. He reckons engine may have lost some comp. I still think it should be better as car runs really well. It's a toyota!! He's going to check for partially blocked cat, put the exhaust analyzer on it.
Why when I disconnect the )2 sensor does it not spit out fault code?
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Location:
Sydney
Registered:
January 2004
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Tue, 11 January 2005 02:06
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If the o2 sensor is hovering between 0.1 and 0.9 volts then this means that according to the 02 sensor it must be hovering around the 14.7 A/F ratio right. If the exhaust gas analyser doesn't show this then it must be an inaccurate O2 sensor right?
THis suggests that the coolant temp sender to ECU and other sensors are ok right. As the system is in closed loop and apparently adjusting mixtures.
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Location:
Sydney
Registered:
January 2004
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Tue, 11 January 2005 06:50
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ANyone fuel economy or 02 sensor experts? 
Thanks
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Location:
NSW
Registered:
January 2005
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Re: Fuel economy Issues *4AFE* - next try O2 Sensor??
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Tue, 11 January 2005 08:42
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Hi i'm only new to this forum so i don't know alot. However I've got a 1995 Holden Nova (rebadge of a toyota corolla ae101r). It has a 4afe engine. I've measured my fuel economy (counted the km's spent from a full and refilled back to full). Well it does about 8.8L/100kms. Just thought i should tell you. The mechanic may be wrong.
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