What Can I Do?
- Thread starter Airedale
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Check all 4 spark plugs,rotor & distributor cap.Then clean the throttle body and replace the oxygen sensor.Also pull the ECU codes incase a part is an electronic sensor is faulty or bad wiring.
Usually excessive short trip city miles combined with low octane gasoline causes excessive carbon build up in the throttle body which does not allow sufficient airflow and hence the butterfly flap/accelerator plate to close all the way.
To clean the throttle body remove the air intake hose and examine the intake and throttle body for excessive carbon build if found then buy a can of throttle body cleaner labeled "safe on oxygen sensors,TPS's and catalytic converters" do not use carb cleaner make sure your engine is fully warmed up prior to using as when the throttle body is hot it dissolves the carbon easily and quickly.The labels usually specify to park the vehicle at ground level (0 degrees,no inclination) and have the engine running but I disagree I instead park the vehicle on a hill facing down and shut the engine off and hold a rag below the lip of the throttle body and poor the stuff and use a tooth brush.
Pulling the ECU codes is the first thing I do to diagnosis a problem thereafter I reset the ECU to see if the same problems show up and if so I then take voltage measurements both with the engine running and not and compare with the factory service manual,I also close the ignition switch after a cold engine and also after a warm engine and compare them with the factory service manual.This technique will completely isolate your problem without having to do trial and error and it is the technique I use when repairing tv's,vcr's,home/car audio.
The oxygen sensor is replaced for free in the USA only when the vehicle reaches it's first 80 000 miles regardless of the age & number of owners as stated in the factory owner's manual in the maintenance section,some Toyota dealerships are reluctant to replace it for free if that happens contact the Toyota regional head office for your region where they will give your local dealership 48 hours to comply.
On average the oxygen sensors should be replaced every 6 years or 100 000 miles or so which ever comes first as stated in the owner's manual,warranty booklet and factory service manual.
Symptoms of a bad o2 sensor are poor gas mileage,hesistation in acceleration,worse emmissions,and in severe cases after the stat opens the engine can no longer maintain stable 750 rpm (with manual 5 spd tranny) idle and the engine begins to stall.
The 02 sensor is designed to function once the vehicle has warmed up which is about after 10 minutes where the thermostat begins to open at 190 or 195 degrees Ferenheit depending on thermostat then the vehicles ECU system enters what they call a "closed loop system" then the exhaust manifold's temperature reaches 400 degree Ferenheit (I think)that's where the sensor starts to do it's job which is usually when the thermostat first opens up then the oxygen sensor senses the ratio of air to fuel and sends a signal back to the ECU then ECU compensates by increasing or decrease the open time for the fuel injectors to pump fuel.So usually the problem of stalling shows up after about 10 minutes of driving or so.Many folks think that the o2 sensor is bad but an exhaust leak can cause excess oxygen to enter the exhaust system thereby fooling the sensor into thinking there is too much oxygen,there are other problems that could cause it to give false reading such as a vaccuum leak.
If you discover that the o2 sensor is bad and it is not under warranty then from my/others experience/research purchase an o2 sensor in the following order:
1)Toyota (NipponDenso now called Denso)
2)Denso aftermarket (Same as original but sold aftermarket)
3)NTK (oxygen sensor division of NGK)
Available at:
http://www.1sttoyotaparts.com/partscat.html (10% shipping by Fed Ex or free shipping with $100 & over speak to Roger at 1-888-271-3948
http://www.Toyotaparts4U.com
http://www.toyotaofplano.com
http://www.densoaftermarket.com
http://www.ngksparkplugs.com
before you replace the oxygen sensor soak the 14 mm brass nuts with any of these deep penetrating oils several times for several hours:
1)PB Blaster
2)Liquid Wrench
3)Kroil Oil
4)Aero Kroil & Sili Kroil
5)Toyota Rust Penetrant or High Performance Penetrating lube
6)Rust Check
the first ones being the best,also if you decide you need new ones here is the Toyota part for the exhaust manifold (brass)nuts # 90179-10175 (14 mm socket)
Oh yeah,I bought a NTK (NGK) oxygen sensor # 24105 for my 85 4-Runner and it came with a gasket and a genuine made in Japan black plastic tie wrap I don't know if the Toyota or Denso aftermarket ones come with a gasket but ask them before you buy them.
Sidney
Usually excessive short trip city miles combined with low octane gasoline causes excessive carbon build up in the throttle body which does not allow sufficient airflow and hence the butterfly flap/accelerator plate to close all the way.
To clean the throttle body remove the air intake hose and examine the intake and throttle body for excessive carbon build if found then buy a can of throttle body cleaner labeled "safe on oxygen sensors,TPS's and catalytic converters" do not use carb cleaner make sure your engine is fully warmed up prior to using as when the throttle body is hot it dissolves the carbon easily and quickly.The labels usually specify to park the vehicle at ground level (0 degrees,no inclination) and have the engine running but I disagree I instead park the vehicle on a hill facing down and shut the engine off and hold a rag below the lip of the throttle body and poor the stuff and use a tooth brush.
Pulling the ECU codes is the first thing I do to diagnosis a problem thereafter I reset the ECU to see if the same problems show up and if so I then take voltage measurements both with the engine running and not and compare with the factory service manual,I also close the ignition switch after a cold engine and also after a warm engine and compare them with the factory service manual.This technique will completely isolate your problem without having to do trial and error and it is the technique I use when repairing tv's,vcr's,home/car audio.
The oxygen sensor is replaced for free in the USA only when the vehicle reaches it's first 80 000 miles regardless of the age & number of owners as stated in the factory owner's manual in the maintenance section,some Toyota dealerships are reluctant to replace it for free if that happens contact the Toyota regional head office for your region where they will give your local dealership 48 hours to comply.
On average the oxygen sensors should be replaced every 6 years or 100 000 miles or so which ever comes first as stated in the owner's manual,warranty booklet and factory service manual.
Symptoms of a bad o2 sensor are poor gas mileage,hesistation in acceleration,worse emmissions,and in severe cases after the stat opens the engine can no longer maintain stable 750 rpm (with manual 5 spd tranny) idle and the engine begins to stall.
The 02 sensor is designed to function once the vehicle has warmed up which is about after 10 minutes where the thermostat begins to open at 190 or 195 degrees Ferenheit depending on thermostat then the vehicles ECU system enters what they call a "closed loop system" then the exhaust manifold's temperature reaches 400 degree Ferenheit (I think)that's where the sensor starts to do it's job which is usually when the thermostat first opens up then the oxygen sensor senses the ratio of air to fuel and sends a signal back to the ECU then ECU compensates by increasing or decrease the open time for the fuel injectors to pump fuel.So usually the problem of stalling shows up after about 10 minutes of driving or so.Many folks think that the o2 sensor is bad but an exhaust leak can cause excess oxygen to enter the exhaust system thereby fooling the sensor into thinking there is too much oxygen,there are other problems that could cause it to give false reading such as a vaccuum leak.
If you discover that the o2 sensor is bad and it is not under warranty then from my/others experience/research purchase an o2 sensor in the following order:
1)Toyota (NipponDenso now called Denso)
2)Denso aftermarket (Same as original but sold aftermarket)
3)NTK (oxygen sensor division of NGK)
Available at:
http://www.1sttoyotaparts.com/partscat.html (10% shipping by Fed Ex or free shipping with $100 & over speak to Roger at 1-888-271-3948
http://www.Toyotaparts4U.com
http://www.toyotaofplano.com
http://www.densoaftermarket.com
http://www.ngksparkplugs.com
before you replace the oxygen sensor soak the 14 mm brass nuts with any of these deep penetrating oils several times for several hours:
1)PB Blaster
2)Liquid Wrench
3)Kroil Oil
4)Aero Kroil & Sili Kroil
5)Toyota Rust Penetrant or High Performance Penetrating lube
6)Rust Check
the first ones being the best,also if you decide you need new ones here is the Toyota part for the exhaust manifold (brass)nuts # 90179-10175 (14 mm socket)
Oh yeah,I bought a NTK (NGK) oxygen sensor # 24105 for my 85 4-Runner and it came with a gasket and a genuine made in Japan black plastic tie wrap I don't know if the Toyota or Denso aftermarket ones come with a gasket but ask them before you buy them.
Sidney
gohawks444
New member
What motor do you have? and what transmission?
If you have the 3.0 and an auto tranny there isn't much you can do, that is what you should be getting, maybe even a bit on the high side.
If you have the 3.0 and an auto tranny there isn't much you can do, that is what you should be getting, maybe even a bit on the high side.
mikes4runner
New member
4x4Ratty said:
Your running 33's so 215MPG is great.
I run 31's and can get 260 and on a highway trip can get 300
Changed the fuel filter recently?
: Also the other things mentioned help too.
Mike
