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Discussion Starter #1
My car is 07 ZO6 and since I have had the car I used ethanol free 93 oct. gas. I found with some help that I am running rich and was told to use E10 93 oct. gas. I was wondering what the rest of u ZO6 people use.
Thanks for the info. in advance Steve
 

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This far north and at altitude we can only get 91 octane. I don't use ethanol. Don't like it even in vehicles said to be built for it with seals that won't deteriorate. Especially I would not like it to sit for long periods over the winter even with additives. Moisture in the gas line in Montana climate is not a good thing. Not worth the hassle as far as I'm concerned.
 

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Discussion Starter #5
I was worried about the same things but am trying to get car to run leaner ( running to rich ) was wondering about moisture forming in gas. Any other problems?
 

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I should have been more precise when speaking of "moisture". My understanding is that as the fuel sits in the tank over time ethanol separates from the rest of the fuel-sort of like what happens when a fuel storage tank isn't full and you get a frost line above the fuel such that when the frost melts you get "moisture" in the fuel line and potential frozen fuel lines. Maybe it is not a problem where ever you live. Also, if you get the ethanol fuel from a gas station that keeps fresh fuel-some place that pumps a lot of it-and you burn it regularly, maybe you have no issues with the ethanol part. I don't really know anything about ethanol except that since I stay away from it completely, I can remain safely ignorant-something my wife thinks I do regularly anyway!
 

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Discussion Starter #7
I have a boat that I ran E10 gas in and ended up having to drain the fuel tank and add a fuel / water separator to fix it. The boat and the vette are the same they spend alot of time setting in garage. What do you all do to combat the problem? Buy the way I'm in Virginia gets pretty cold here also.
 

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What mods have been done and what method is being used to determine its too rich? The factory tune will be richer than ideal at wot but should be spot on during closed loop cruising; changing to E10 from E0 gas isn't going to fix that situation as the car was factory tuned with tolerances to run either type of gas. If its running rich its most likely because something has been altered hardware wise or is missing/failed. If the car has been modified then getting it tuned for the hardware changes is the answer. A common modification that will cause a car to run richer at wot than normal is changing the free flowing air filter setup. The ecu compensates for it during closed loop cruising but then adds that compensation during wot which typically leads to overly rich condition. The fix is to have it properly tuned so the ecu understands the maf model among other things.
 

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Because of E10/E15 mandated gas which induces engine knock and yanked timing GM biased the tune RICH by about -7% as E10 alone leans up AFR about 7-8%
Add higher elevation AFR would even be richer.

Now use Non Ethanol gas, losing the leanness of E10 and you end up too rich
Add colder weather and more richer on cold starts but as OP stated using a scanner the fuel trims (non WOT) are way too rich and that is a stock Z06 with a 3rd party air-filter adds to super rich on cold startup which is the OP complaint
In the end engine running for some time with dirty air-filter, leaking airbridge, 17-20 % too rich would end up with lots of carbon buildup and also effecting cold starts.

Going to E10 will help reduce that too rich AFR at that elevation and by use of scanner know what AFR is on colder days, cold start and what AFR is on hot summer days using non Ethanol fuel.
 

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E10 should only affect afr and mpg around 3% assuming it's compared to same octane level of E0. At full tilt the E0 should make more power even if running richer by that % and resist knock better. Is it worth the price that is up to you. E85 and E100 have some advantages since its higher octane than E0 premium so more ignition can be used which is great for forced induction engines.
 

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3% is too low of effects of E10 over weather and elevation changes

The C6 Z06 427 LS7 runs hotter then LS3s do, this alone induces more engine knock and cost of performance numbers GM would not want

As compared views below GM had to set the C6 Z06 LS7 tune for fuel trims from 5 to 8% richer (to make up the 7% leaner due to E10)
(then what C5 Z06 LS6 AFR was set to) from idle to even only 2,500 RPMs
As the elevation, air and coolant temps go up the PCM is slanted to go even richer

Makes no difference what non Ethanol or high amounts of Ethanol used as this OP is about running too rich at startup and idle - what the causes were
OP had car to dealer for some days and they could not find any problem ( as AFR is GM set to rich)

The fact GM had to slant the fuel trims richer due to E10 where they did not for older Corvettes that the E10 had ill effects to AFR so C6s had to be set richer in GM calibrations

So if the engine at cold start and idle is running -8% rich fuel trims with E10 as GM tunes below shows rather then for years running a 14.2:1 (stoch) AFR GM had to lower that to 13.9:1
That means GM tune is set to on purpose command richer AFR to help reduce the engine knock from E10

Now when the OP has a dirty air cleaner (less airmass) and using non Ethanol gas the fuel trims then will be even richer and that is what the OP found doing OBD-II scans where on cold start
the fuel trims were 15% plus too rich. Will not make a good cold start

So a tuner says, clean air cleaner and run some E10 and using a scanner see what the effects are and what the fuel trims then look like when driving at their higher elevation
 

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Discussion Starter #12
The car has only 1 mod. a CA intake. I also put in chevy dealer shop and had tune checked and updated to make sure it was stock tune.After cleaning MAF, Checked found and fixed air leak in CA intake,new plugs & wires and after sitting a few days started and ran very rough for about 20-30 sec. then ran great. I cleaned MAF again only this time I didn't care if I messed it up so I soaked it good inside and out with MAF cleaner but didn't have time to let it set before going to dealer. Dealer said after 3 days started and ran smooth. He ran his diagnostics on car and found nothing out of range.Following JR's advice I am now running Shell 93 oct. E10 gas with sea foam ( just started only about 50 mi. so far ) and cleaned air filter really good. So starting trbl. seams to be OK but still running rich by my scanner. Will post what happens after driving awhile.
buy the way corvette guy at Dealer said all is within normal operating range and I may be trying to fix something that is not broke
Thanks for taking time to read and your advice Steve
 

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3% is too low of effects of E10 over weather and elevation changes

The C6 Z06 427 LS7 runs hotter then LS3s do, this alone induces more engine knock and cost of performance numbers GM would not want

As compared views below GM had to set the C6 Z06 LS7 tune for fuel trims from 5 to 8% richer (to make up the 7% leaner due to E10)
(then what C5 Z06 LS6 AFR was set to) from idle to even only 2,500 RPMs
As the elevation, air and coolant temps go up the PCM is slanted to go even richer

Makes no difference what non Ethanol or high amounts of Ethanol used as this OP is about running too rich at startup and idle - what the causes were
OP had car to dealer for some days and they could not find any problem ( as AFR is GM set to rich)

The fact GM had to slant the fuel trims richer due to E10 where they did not for older Corvettes that the E10 had ill effects to AFR so C6s had to be set richer in GM calibrations

So if the engine at cold start and idle is running -8% rich fuel trims with E10 as GM tunes below shows rather then for years running a 14.2:1 (stoch) AFR GM had to lower that to 13.9:1
That means GM tune is set to on purpose command richer AFR to help reduce the engine knock from E10

Now when the OP has a dirty air cleaner (less airmass) and using non Ethanol gas the fuel trims then will be even richer and that is what the OP found doing OBD-II scans where on cold start
the fuel trims were 15% plus too rich. Will not make a good cold start

So a tuner says, clean air cleaner and run some E10 and using a scanner see what the effects are and what the fuel trims then look like when driving at their higher elevation
The 04 Z06 has a unique ls6 pe tune that is leaner than other year ls6's. Perhaps on purpose, perhaps a mistake by gm releasing that pe model in that 1 year. The other ls6 years have a pe table similar to the ls7. The other tables referring to stoich are pointless to discuss since neither c5 or c6 came with a alcohol sensor to make actual use of those settings. The ecu in the c6 was used in other flex fuel vehicles so that table exists doesn't mean its actually used. Use whatever gas you want but at the track under fill tilt the E0 will make more power and be safer for the vehicle. I can't image any tuner suggesting E10 in any performance vehicle unless they are a farmer. If you want to tune the car then the conversation is different, both cars were tuned for E0 but will accept E10 without an issue due to the minimal 3% stoich difference.
 

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The CAI is causing the issue, go back to stock hardware setup or make sure the CAI is sealed properly and have the car tuned by a professional. When its tuned they can also lean out the pe some as well. Run E10 or E0 but its not going to fix a vehicles rich condition in general. The way a car adapts during closed loop ltft processing will never be corrected by fuel type change if the maf transfer model is off due to hardware changes. In a full tilt situation E0 is preferred to E10 as it has more potential energy.
 

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The CAI is causing the issue, go back to stock hardware setup or make sure the CAI is sealed properly and have the car tuned by a professional. When its tuned they can also lean out the pe some as well. Run E10 or E0 but its not going to fix a vehicles rich condition in general. The way a car adapts during closed loop ltft processing will never be corrected by fuel type change if the maf transfer model is off due to hardware changes. In a full tilt situation E0 is preferred to E10 as it has more potential energy.
Not a good response, the OP has GM warranty and a tune is out of the question for him, that is is choosing
That is like putting a band-aid on a problem and hoping that will cure the problem

You really need to go learn about Ethanol, it is far proven it reduces fuel mileage, induces lean fuel trims so much so the feds had to put out notice out to NOT use Ethanol in most other gas engines.
Have no idea why since you do not know that history or the OPs Z06, nor looked at his OBS-II scanner recordings, nor understanding the ill effects of running 17-20 % rich what the effects are to internal of some engine parts, to O2 sensors or even the fact running that rich is degrading the life of the CATS,

No valid to want to run a non Ethanol fuel that runs richer when the fuel trims are at the trigger point for rich DTCs. OP needs to get engine BACK to leaner fuel trims
BEFORE going back to non Ethanol gas and his scanner will tell him when trims are back to normal

No do I have a clue why your on engine functions like WOT when the engine would not run correctly on a COLD start only

OP is doing the right thing, correcting things found by his tuner, cleaning out the carbon from running so rich for some time,
as changes he makes using the scanner to see if the fuel trims become normal and using some E10 gas to then see what the fuel trims are like
For a car that is not raced, it barely would see issues related to fuel trims but to determine rich fuel trims he is going the right path in
doing changes, even the gas to get fuel trims correct

Your method or mindset is not correct path for a stock Z06 that GM tuned richer solely because of E10 running leaner

-----------------------------------------------------
People are up in arms over recent EPA waivers that allow but do not require up to 15 percent ethanol to be blended into gasoline as E10 is already too lean for pre 2008 vehicles .
The 15 percent blend, called E15, would be available only from blender pumps clearly labeled “Passenger vehicles only.
Use in other vehicles, engines and equipment may violate Federal law.”

Here is the EPA’s list of vehicles that should not be fueled with E15:

Motorcycles

Vehicles with heavy-duty engines, such as school buses and delivery trucks

Off-road vehicles, such as boats and snowmobiles

Engines in off-road equipment, such as lawnmowers and chainsaws

Model-year 2000 and older cars, light-duty trucks and medium-duty passenger vehicles (later changed to model-year 2007 and older)

**** Because ethanol contains one-third less energy per gallon than gasoline, adding ethanol to gasoline leans out the fuel-air mixture, possibly enough to cause damage.
Several manufacturers have said they will not honor warranties if fuels containing more than 10 percent ethanol are used.
That includes GM.
Pre 2008 vehicles including Corvettes were not designed even for E10, GM had so many customer problems that cars like the C6 had to be slanted richer,
C5s the PCM used a algorithm of what fuel trims and O2 outputs to determine gas quality

In the end the OP has been doing as his tuner proposed and that found the airbridge leak, the dirty aircleaner, the coked up valves, piston tops and lazy O2 sensors
and final test of using some E10 gas will pinpoint if start problems are gone, what the fuel trims are now and then can go back to fuel he wants that work on a
stock engine under GM warranty.

A tune setup for using non Ethanol gas would have the most performance benefit but only when owner wants to go that route, and lastly learn about elevation, density and the grades of gas sold in higher elevation
 

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The car has only 1 mod. a CA intake. I also put in chevy dealer shop and had tune checked and updated to make sure it was stock tune.After cleaning MAF, Checked found and fixed air leak in CA intake,new plugs & wires and after sitting a few days started and ran very rough for about 20-30 sec. then ran great. I cleaned MAF again only this time I didn't care if I messed it up so I soaked it good inside and out with MAF cleaner but didn't have time to let it set before going to dealer. Dealer said after 3 days started and ran smooth. He ran his diagnostics on car and found nothing out of range.Following JR's advice I am now running Shell 93 oct. E10 gas with sea foam ( just started only about 50 mi. so far ) and cleaned air filter really good. So starting trbl. seams to be OK but still running rich by my scanner. Will post what happens after driving awhile.
buy the way corvette guy at Dealer said all is within normal operating range and I may be trying to fix something that is not broke
Thanks for taking time to read and your advice Steve
Steve I had the tuner email the recording data he was nice enough to look at for you as a favor to me and your doing a right path with the changes he told you to do and as he requested a drive with scanner recording now with and without E10 gas and see what the fuel trims are now like. Would take some driving before the fuel trims start moving leaner.
That data as shown below cold start at 59 degrees coolant and how rich both the long and short fuel trims been running quite rich for some time and Cats working harder to convert the rich exhaust to leaner out to mufflers

Let us know what the fuel trims look like now with the E10 and can judge what to do when seeing that data.
 

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Discussion Starter #17
Thanks racingvette, you and JR have been a GREAT help to me. I think the starting trbl. is OK now. don't know exactly what fixed it. It's been rainy weather here and when it clears up I will run it a 100-150 mi and send JR or you the data. Again I can't tell you how much you guys have helped.
Thanks Steve
by the way this tank of fuel is a mix about 3/8 reg. 93 oct. & about 5/8 E10. next tank may do better
 

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Good to hear Steve,
Your Welcome and glad to be of some help for your Z06 problems

Get a scanner recording and email to tuner as I asked him and he said it was OK to do so
Then let us know what he sees as to your fuel trim values.
 

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Steve the tuner emailed me and asked if I would attach your last scanner recording values since you did not know to do it
Even though you mixed some E10 with the non Ethanol fuel and first drive the OBD-II scanner shows the fuel trims have already coming down and close what would
be seen with E10,
Once you get through that tank and then full tank of E10 the fuel trim values should be even better.
Values seen on this drive are about what was expected where before fuel trims were -17-20 plus percent rich and now about -8% rich and that is in 56 degree weather
You could look next year summer heat what fuel trims look like and decide which fuel is good at the 2500-3000 feet elevation but since you only do street speeds
it may not be worth the high cost of non Ethanol gas at that elevation since the GM tune is slanted for E10

Later on when not worrying about GM warranty you could consider having a custom tune done to allow for the better non Ethanol gas and the performance gains of that fuel
and tune gains

Nice to see the cold start issue now gone

Suggestions were :

Put that other half of Seafoam into intake manifold while at idle, if cannot do that put in engine oil
Since the engine has been running way rich for months is take sparkplugs out, clean and re-gap them
Take front O2 sensors out and use a propane torch to heat up ONLY tips of them to burn off any carbon buildup
To limit blowby and engine reverb is next time changing engine oil to go with a bit on oil viscosity

Use lower gears to use higher RPMs ( rather then high speeds) and loads to help blow out carbon and allow PCM to learn/adjust fuel trims for all engine loads
and allow the carbon breakup from the Seaform to exhaust out.
 

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The CAI is causing the issue, go back to stock hardware setup or make sure the CAI is sealed properly and have the car tuned by a professional. When its tuned they can also lean out the pe some as well. Run E10 or E0 but its not going to fix a vehicles rich condition in general. The way a car adapts during closed loop ltft processing will never be corrected by fuel type change if the maf transfer model is off due to hardware changes. In a full tilt situation E0 is preferred to E10 as it has more potential energy.
Not a good response, the OP has GM warranty and a tune is out of the question for him, that is is choosing
That is like putting a band-aid on a problem and hoping that will cure the problem

You really need to go learn about Ethanol, it is far proven it reduces fuel mileage, induces lean fuel trims so much so the feds had to put out notice out to NOT use Ethanol in most other gas engines.
Have no idea why since you do not know that history or the OPs Z06, nor looked at his OBS-II scanner recordings, nor understanding the ill effects of running 17-20 % rich what the effects are to internal of some engine parts, to O2 sensors or even the fact running that rich is degrading the life of the CATS,

No valid to want to run a non Ethanol fuel that runs richer when the fuel trims are at the trigger point for rich DTCs. OP needs to get engine BACK to leaner fuel trims
BEFORE going back to non Ethanol gas and his scanner will tell him when trims are back to normal

No do I have a clue why your on engine functions like WOT when the engine would not run correctly on a COLD start only

OP is doing the right thing, correcting things found by his tuner, cleaning out the carbon from running so rich for some time,
as changes he makes using the scanner to see if the fuel trims become normal and using some E10 gas to then see what the fuel trims are like
For a car that is not raced, it barely would see issues related to fuel trims but to determine rich fuel trims he is going the right path in
doing changes, even the gas to get fuel trims correct

Your method or mindset is not correct path for a stock Z06 that GM tuned richer solely because of E10 running leaner

-----------------------------------------------------
People are up in arms over recent EPA waivers that allow but do not require up to 15 percent ethanol to be blended into gasoline as E10 is already too lean for pre 2008 vehicles .
The 15 percent blend, called E15, would be available only from blender pumps clearly labeled “Passenger vehicles only.
Use in other vehicles, engines and equipment may violate Federal law.”

Here is the EPA’s list of vehicles that should not be fueled with E15:

Motorcycles

Vehicles with heavy-duty engines, such as school buses and delivery trucks

Off-road vehicles, such as boats and snowmobiles

Engines in off-road equipment, such as lawnmowers and chainsaws

Model-year 2000 and older cars, light-duty trucks and medium-duty passenger vehicles (later changed to model-year 2007 and older)

**** Because ethanol contains one-third less energy per gallon than gasoline, adding ethanol to gasoline leans out the fuel-air mixture, possibly enough to cause damage.
Several manufacturers have said they will not honor warranties if fuels containing more than 10 percent ethanol are used.
That includes GM.
Pre 2008 vehicles including Corvettes were not designed even for E10, GM had so many customer problems that cars like the C6 had to be slanted richer,
C5s the PCM used a algorithm of what fuel trims and O2 outputs to determine gas quality

In the end the OP has been doing as his tuner proposed and that found the airbridge leak, the dirty aircleaner, the coked up valves, piston tops and lazy O2 sensors
and final test of using some E10 gas will pinpoint if start problems are gone, what the fuel trims are now and then can go back to fuel he wants that work on a
stock engine under GM warranty.

A tune setup for using non Ethanol gas would have the most performance benefit but only when owner wants to go that route, and lastly learn about elevation, density and the grades of gas sold in higher elevation
The mindset is correct remove the hardware in this case cai and go from there if tuning is not an option. E10 is not going to solve an overly rich situation in a car that runs in closed loop. If the car only ran open loop then that is another story. If this guy fixed his car it's because the cai is now sealed or installed correctly.
 
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