Excessive Fuel Consumption
08-01-2010, 11:42 PM
#21
That is the complete opposite from what I have read.
A downstream oxygen sensor in or behind the catalytic converter works exactly the same as an upstream O2 sensor in the exhaust manifold. The sensor produces a voltage that changes when the amount of unburned oxygen in the exhaust changes. If the O2 sensor is a traditional zirconia type sensor, the voltage output drops to about 0.2 volts when the fuel mixture is lean (more oxygen in the exhaust). When the fuel mixture is rich (less oxygen in the exhaust), the sensor's output jumps up to a high of about 0.9 volts. The high or low voltage signal tells the PCM the fuel mixture is rich or lean.
A downstream oxygen sensor in or behind the catalytic converter works exactly the same as an upstream O2 sensor in the exhaust manifold. The sensor produces a voltage that changes when the amount of unburned oxygen in the exhaust changes. If the O2 sensor is a traditional zirconia type sensor, the voltage output drops to about 0.2 volts when the fuel mixture is lean (more oxygen in the exhaust). When the fuel mixture is rich (less oxygen in the exhaust), the sensor's output jumps up to a high of about 0.9 volts. The high or low voltage signal tells the PCM the fuel mixture is rich or lean.
08-02-2010, 07:14 AM
#23
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Heres the latest. Just filled up. Gauge read 1/8 tank and it took 10.9gal. so the gayge is reading correctly. That means the gauge can now be taken out of the equation. With that eliminated, I can now move onto either a sensor or objectors issue. This is the 1 reason I love my 67 much better than this. With the 67 there can only be a few things. With this, that list Is infinate.
BTW, the trip odometer read 211 miles and that was whike using at least 85% highway.
BTW, the trip odometer read 211 miles and that was whike using at least 85% highway.
Last edited by 02 CamaroSS; 08-02-2010 at 07:19 AM. Reason: added info
08-02-2010, 07:39 AM
#24
I couldn't get 200 downhill with the wind behind me. As for the injectors, is a leaking objectors going to give u different voltage reference when tested than a properly working 1? I can't wrap my head around the downstream o2's being cat ONLY monitors and only staying at the either end of the voltage range. That would mean they would tell the pcm the cat isnt doing its job and the pcm would act accordingly. on the other hand, if the.sensors were.bad, the engine light would turn on.
What does your exhaust smell like? Are you getting backfires? If your mileage is really this low, you may have multiple issues? Maybe a neighbor is siphoning gas out of your tank?
08-02-2010, 08:00 AM
#26
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[QUOTE=wssix99;13679921]There is a footnote in the factory service manual. The post cat sensors DO impact long term fuel trim. (in addition to monitoring the cat) As the sensors foul, its hard for the PCM to tell if the sensor is bad or reading a problem. You'll often get a O2-specific code for the pre-cat sensors and may see a cat-specific code or condition when the post-cat sensors go bad. Even with these codes, you may not get a SES light.
What does your exhaust smell like? Are you getting backfires? If your mileage is really this low, you may have multiple issues? Maybe a neighbor is siphoning gas out of your tank?[/QUOTE
I never thought about someone stealing gas, but anything is possible these days. I kinda figured they were there for more than just a caf minitor. I'm not getting any backfires, but as I mentioned, somewhere between 4000-5000, under wot she stops pulling and with a z06 can and valve springs that is right where she should start pulling the hardest. I wanted to go to a locking cap, but want to keep the strap that keeps the cap from getting lost.
What does your exhaust smell like? Are you getting backfires? If your mileage is really this low, you may have multiple issues? Maybe a neighbor is siphoning gas out of your tank?[/QUOTE
I never thought about someone stealing gas, but anything is possible these days. I kinda figured they were there for more than just a caf minitor. I'm not getting any backfires, but as I mentioned, somewhere between 4000-5000, under wot she stops pulling and with a z06 can and valve springs that is right where she should start pulling the hardest. I wanted to go to a locking cap, but want to keep the strap that keeps the cap from getting lost.
08-02-2010, 08:03 AM
#27
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08-03-2010, 10:27 AM
#30
BUT....a dirty or even a failed MAF cannot kill your gas mileage. The MAF is only operating during cold start-up and when you are at WOT.
.
Last edited by LS6427; 08-03-2010 at 11:11 AM.
08-03-2010, 12:54 PM
#31
It would only negatively affect the mileage if it was REALLY REALLY dirty. Even then, it wouldn't be this much.
I had a similar problem, not quite as bad, and it turned out to be a leaking injector. Probably paid for the new one in gas in about 2 fill ups
I had a similar problem, not quite as bad, and it turned out to be a leaking injector. Probably paid for the new one in gas in about 2 fill ups
08-03-2010, 09:37 PM
#32
The MAF will not be related to the fuel problem but could be why you are stalling out at high RPM. A dirty MAF usually cuts fuel usage because it doesn't sense enough air coming in to the engine.
08-05-2010, 11:09 AM
#34
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have you checked your tire air pressure, how clean is your air filter. what is the condition of your spark plugs and wires. how about the coils, maybe they are starting to wear out.
08-05-2010, 11:22 AM
#35
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Tire prrssure Is set to sticker on door, filter brand new, plugs look good, not sure about wires or coils but the car starts flawlessly every time. What is the resistance the coils are supposed to read in high/low sides?
08-05-2010, 05:11 PM
#36
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What the chance, even thouhg the o2's are responding, that they are r getting slow? How fast should the voltage change b while at Idle? Should the change b immediate or should.there b a slight pausr between each change?
08-06-2010, 01:23 PM
#37
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There is another issue present along with the excessive fuel consumption. When I get to about 4000-4500rpm, the car hits a flat spot and no longer pulls hard. From idle to 4/4.5k all is great, but once I get to that rpm, she falls flat. The engine has a 2002 z06 camshaft and valve springs so 4/4.5k Is right where the engine should come alive and should pull harder than idle-4/4.5k. The 2 issues r related. Just changed fuel filter.
Is there a way 2 test an injector ON THE CAR, for leaking? If I had the money, I would replace all 8 along with all 4 o2's, but I don't so j need a way to test the injectors for leaks.
Is there a way 2 test an injector ON THE CAR, for leaking? If I had the money, I would replace all 8 along with all 4 o2's, but I don't so j need a way to test the injectors for leaks.
08-06-2010, 07:47 PM
#38
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Here's the latest. I pulled the plugs and according to the owners manual, the plug gap is supposed to be .060". The gap was set at .037". I'm not sure about fuel mileage, but I'm pretty confident the gap has a lot to do with my 4/4.5k flat spot.
Can someone please tell me how the help u get 4/6/8 plugs out? No way in hell from top and I don't even see a way from bottom.
Can someone please tell me how the help u get 4/6/8 plugs out? No way in hell from top and I don't even see a way from bottom.
Last edited by 02 CamaroSS; 08-06-2010 at 08:28 PM.
08-06-2010, 09:08 PM
#39
Here's the latest. I pulled the plugs and according to the owners manual, the plug gap is supposed to be .060". The gap was set at .037". I'm not sure about fuel mileage, but I'm pretty confident the gap has a lot to do with my 4/4.5k flat spot.
Can someone please tell me how the help u get 4/6/8 plugs out? No way in hell from top and I don't even see a way from bottom.
Can someone please tell me how the help u get 4/6/8 plugs out? No way in hell from top and I don't even see a way from bottom.
08-06-2010, 09:41 PM
#40
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my socket has the indentations for use with a wrench. a also have a flex socket for tight spaces, both worked from the top. i also unhooked the heat riser off of the passenger side exhaust manifold. ( i dont have headers yet )