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10 miles per gallon

bdimag

bdimag

abandon all hope
Joined
Oct 10, 2007
Location
Northern VA
the problem has been around since i bought the car, except then it was 14mpg... mostly everything was replaced by the dealer just before I bought it.

I had these codes:
1-1-3
2-3-2

I checked the O2 sensor and got a constant .019v with no variation whatsoever, so i replaced it today... the old one was COVERED in blackness...

Before i started up, i reset the codes and then to make sure, I tried to read them. LOUD RAPID CLICKING coming from somewhere in the middle or near the other side of the bay, and the OBD light was flashing rapidly...

start car; CEL:
1-1-3
2-2-1
2-3-2

short drive; same issues... reset codes and then tried to read again, flashing light but no clicking.

O2 is not reading a constant-never-changing .026v

------------
replaced by me:
o2
maf

replaced by dealer:
ECT
O2 (the one i just replaced)
airbox thermo.
vacuum lines
FPR

replaced by indy shop:
fuel computer




thoughts?
:please:



also quick question: if the cold start injector was dumping fuel, would these o2 readings be considered correct? one being slightly higher because it's not covered in crap...
 
cracked manifold? Some sort of intake gasket leak? I have a suburban that suffered the same thing, but to get 5mpg while towing when i am used to 11 shot my trip all to hell. looked at and replaced alot of things, until I pulled the stock heat sheilds off the manifolds to find that between the 2-4 junction it was almost cracked all the way around. Weird thing tho is I did not hear it and my O2 actualy was reading fine, just running hella rich.
 
The very low voltage on the O2 sensor is telling the fuel computer the engine is very lean which would make the fuel computer try to richen up the mixture. So, it seems to me that the cause is something making the O2 sensor give a false voltage. Do you have a good ground on the valve cover to the firewall? How about the grounds on the intake manifold? Also check the plug gap to be sure it's within spec.

You are running the engine long enough that it should go into closed loop operation when you take this voltage reading? Even with a heated O2 sensor it still takes a few minutes of operation before it's hot enough for closed loop. So, the first few minutes the engine should run rich and the sensor could have an erroneous reading. But once it's warmed up the sensor should be oscillating. I would go back and check the engine coolant sensor. Be sure to check it's resistance cold, warm and fully up to operating temp. It's a sensor that overrides closed loop and would make the engine run very rich. I've seen the sensor have acceptable resistance when cold and warm but open to infinite ohms when hot which does what I described to the engine. Just because it was replaced doesn't mean it's working correctly.
 
are you testing the o2 with a multimeter? Because and o2 cycles too fast for a digital multimeter to accuratly read it. But as said, its leaning out. Change gaskets, look at FPR.
 
Had the exact same issue on our 99 XC70, right down to blowing all kinds of money on parts that didn't fix the problem. Traded it in on a 2010 Subaru Outback, problem completely went away.
 
Based on the fact that it's running really rich and the O2 sensor is indicating very lean I'd check for cracks in the exhaust manifold and exhaust pipe before the sensor. Clean your grounds too. Also, verify that your engine isn't burning coolant or large amounts of oil, both of those things can cause O2 sensor contamination and very low voltage readings.
 
Run some seafoam through it.

Have you tested the injectors?

New Throttle Positioning Switch.

Fuel Filter, Pump, Intank?

Kink in the line somewhere.
 
Buy a new Nissan Leaf and have 95% of the moving and hot parts go away. 100 mpg, brakes last 100k+ miles, and no emissions testing and gas stations. You can also sneak up on people and run them over if you like.

Now for us:

Alt. regulators control the armature current through voltage sensing from three small sampling diodes on the output windings. The regulator can do about anything, open, short, intermittent. Measure the voltage at the battery posts and fuse block to body ground and it should be 13.5 volts or greater and if it is you are done with that part.

Go to the ECU and measure for supply plus battery and battery ground right at the pins on the cable, if it is OK then you are done with that.

Check for your input sensors at the ECU cable for proper voltages or resistances with the ECU unplugged and if necessary short the sensor leads at the devices and check for low resistance at the ECU connector.

Check for proper voltages or resistances, with the ECU unplugged, for the output signals that control the devices.

A vacuum leak should not make the engine run rich on the intake manifold.

You can get a hint at the O2 voltage with a voltmeter as it is just a varying D.C. voltage, not A.C. The meter should be of decent quality and not load the sensor and have good voltage averaging, the signal changes very slow compared to most devices.

You may also have a mechanical problem, stuck injector, too high fuel pressure, crack in exhaust system bringing in fresh air before the 02 sensor.

Are you sure it is running rich as in smell and/or testing the exhaust or a possible tank or fuel line leak? :rofl:
 
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Make sure your O2 sensor plug is not connected in to the wrong socket. There are two that will interchange... Does your car have a 3 wire or 1 wire sensor? .026v = lean reading.. Your computer is compensating for this lean mixture by adding as much fuel as it can to correct the lean issue. Check for Vacuum leaks, especially at the intake manifold.
 
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