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An exhaust leak prior to the upstream sensors can cause this problem.
Verify the heater circuit on each "upstream sensor" has power. These sensors require electrical heating to function normally. (ECU will typically throw a code for an open O2 heater circuit, but not in every vehicle. Not sure about yours. You should find 12V at the O2 connector with ignition on and engine off. Peck around in the source connector with a voltmeter to verify the presence of 12V for the heater. Do this for both upstream (ahead of cat) O2 sensors.
Until the O2 snesors are hot enough to work (>650 F), the ECU estimates the fuel injection amounts, which are conservative so as not to run lean. At idle the exhaust is not hot enough to maintain the O2 sensor working temp so each one has a 12V electrical heating element built-in to keep them working at stoplights to limit pollution.
That's about it. Upstream exhaust leaks and O2 heater circuits.
Aso, unless the engine requires premium gas, don't use it. It does not help the engine perform. High octane gas burns slower to reduce detonation in high compression and/or boosted performance engines. It does not have more energy.
the heater blower fan is dead, ? this car is wired (im looking in alldata dot com now) gets 12v power from the IGNITION at all times. so there is no blower fuse. (if the fan shorts, the engine fuse blows. and engine dies. the current passes thru motor, and then to the dash speed switch and on level 4 there is no resistor, so must run, here, (does it?) then the switch is grounded. so if engine runs. and speed 4 fails, it can only be. 1: bad ground to switch. 2:bad wires. 3 :bad switch, 4: bad fan, (hot wire fan does it work,. yes, good its good.
id put my DMM across the fan , turn it on, and if 12vdc is across said fan, and it dont blow, its a bad fan. if the low side of fan is not 0v, all times. the ground is bad. if the 12v never reaches the fan, then the path on that side is bad.
could be the blower motor it self. usually when resistor failes the blower will only work on HIGH or number 4 on your dash. when resistor burns out, all speeds other than 4 tend to stop working and blower works on high because its getting 12V/batter voltage applied to it, when on lets say speed number 3 the blower gets less voltage thus resulting is slower operation. put 12V/battery voltage to the blower motor directlly and see if it comes on. it should crank pretty fast so hold it tight when you are ready to put battery voltage to it.
Usually, the 12V runs to a resistor pack mounted to the side of the blower motor. When you use the fan select switch, you change the load on the motor and it goes faster or slower. If the resistor pack is defective, that will cause the motor not to run.
You can pull the motor out and attach one side of the battery to the motor +12V side, and attach the ground to the (-) side of the motor to see if it comes on without going through the resistor pack. If it does, replace the resistor pack. If not, replace the blower motor.
The whole toggle thing sounds like a shortcut was taken to avoid fixing the initial problem.
If the voltage is good to the heater blower motor , try lightly tapping on the motor near the end where the wiring enters while the fan is on.If it runs ,the motor needs replacing.
Is normal for older vehicles to do this. Wait until something breaks and fix it. I know it doesnt sound like great advice, but if all is working,leave it alone.
Check the blower motor under the dash.(on right side put a 12v lead directly to the connection and if it works, the problem may be in the switch relay or resistor pack. (i've also heard of debris holding the fan from moving so if there is power there and motor does not run, remove & check first before buying a new unit.)
how about some more info man. do you mean the heater fan is not blowing air? if that is the case it is easy to fix. most cases it is a fan motor or a blower motor resistor. if you are getting air flow but you can't switch it from hot to cold. it could be a blend door. that is a relativly large job. the dash would have to come out. do the coolant lines to the heater core both get hot? if not the core could be pluged. does your a/c even kick in or work. you could have many problems causing this.
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