Need a little Tech help..... Please!
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Need a little Tech help..... Please!
It is my turn for a little brainstorming from all you guys. My car all the sudden started running very rich and consuming a lot of gas. For those that don't know the car is a 2002 Z06 w/ H/C, LT's, Injectors, Xpipe and all the normal bolt on stuff. After playing around on the Tech II and HP tuners, the short and long term Fuel trims are way up. I am talking like 25%-40% +. If I reset the fuel trim learn, it will start out back at zero and quickly climb back to the 25-40% again within a couple minutes or less. I have no SES light, no surging, high idle, or drivability problems other than a ton of smoke at idle and low RPM's, really poor mileage and a raw fuel (burn your eyes type) smell. I have eliminated a vacuum leak, replaced O2's, MAF and ruled out injectors leaking. The plugs are dark colored, but no signs of damage or closed gaps etc. Also the Compression checks out good (I do not think that would matter). If you have any ideas, I am 
. I have been chasing this down for a couple weeks and would try anything at this point. TIA.
RICH
. I have been chasing this down for a couple weeks and would try anything at this point. TIA. RICH
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From: At the beach in little Rhody
Sounds like it is running lean if it is adding 25-40% fuel or did I misunderstand? That should definitely set a code as I think the threshold for setting is 13% plus or minus (lean or rich). Have you looked at the EVAP system?
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by vettenuts
Sounds like it is running lean if it is adding 25-40% fuel or did I misunderstand? That should definitely set a code as I think the threshold for setting is 13% plus or minus (lean or rich). Have you looked at the EVAP system?
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by vettenuts
Have you tried re-loading the tune?
RICH
Drifting
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From: bloomfield nj
Originally Posted by RichieRichZ06
That will be my next step if nobody has any must try ideas on here. I spoke with Rick at Synergy, eho did the tune, but it is a little drive for me to get down there so it may be a week or two. I am very busy at work lately. Thanks for the tips Vettenuts.
RICH
RICHare you sure you don't have a vacuum leak anywhere.for your #'s it would have to be a large one.do you hear any hiss sound inside the car[i'm assuming you checked everything under the hood],like a leaking brake booster.try pinching off the line and see if the #'s go down. try spraying carb cleaner around the intake/map/vacuum lines,etc and see if the numbers change.
what are the o2 voltages saying[for your trim #s,if you are in fact lean,your o2 voltages would be around 200-300mv]?
what is your map/baro readings[barometric pressure is figured out by the pcm using the map sensor]?
what is fuel pressure/volume[you can have pressure but not enough
volume]?
how does the car run over all[power/no power/sluggish,etc]?
just some thoughts.
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From: Slave to the evil empire
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St. Jude Donor '04
Originally Posted by dpd
are you sure you don't have a vacuum leak anywhere.for your #'s it would have to be a large one.do you hear any hiss sound inside the car[i'm assuming you checked everything under the hood],like a leaking brake booster.try pinching off the line and see if the #'s go down. try spraying carb cleaner around the intake/map/vacuum lines,etc and see if the numbers change.
what are the o2 voltages saying[for your trim #s,if you are in fact lean,your o2 voltages would be around 200-300mv]?
what is your map/baro readings[barometric pressure is figured out by the pcm using the map sensor]?
what is fuel pressure/volume[you can have pressure but not enough
volume]?
how does the car run over all[power/no power/sluggish,etc]?
just some thoughts.
what are the o2 voltages saying[for your trim #s,if you are in fact lean,your o2 voltages would be around 200-300mv]?
what is your map/baro readings[barometric pressure is figured out by the pcm using the map sensor]?
what is fuel pressure/volume[you can have pressure but not enough
volume]?
how does the car run over all[power/no power/sluggish,etc]?
just some thoughts.
You say you replaced the O2 sensors but have you done a scan to what voltages are present?
Tech Contributor
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Rich
Use the tech II to make sure that all of the sensors are working correctly! Especially the temp sensors. if the engine thinks it is very cold out, it will add fuel.
BC
Use the tech II to make sure that all of the sensors are working correctly! Especially the temp sensors. if the engine thinks it is very cold out, it will add fuel.
BC
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by willyfastz
You don't have the plugs switch on the o2's do ya? I've seen one do the same thing and the front o2 plugs were crossed.
Thread Starter
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by dpd
are you sure you don't have a vacuum leak anywhere.for your #'s it would have to be a large one.do you hear any hiss sound inside the car[i'm assuming you checked everything under the hood],like a leaking brake booster.try pinching off the line and see if the #'s go down. try spraying carb cleaner around the intake/map/vacuum lines,etc and see if the numbers change.
what are the o2 voltages saying[for your trim #s,if you are in fact lean,your o2 voltages would be around 200-300mv]?
what is your map/baro readings[barometric pressure is figured out by the pcm using the map sensor]?
what is fuel pressure/volume[you can have pressure but not enough
volume]?
how does the car run over all[power/no power/sluggish,etc]?
just some thoughts.
what are the o2 voltages saying[for your trim #s,if you are in fact lean,your o2 voltages would be around 200-300mv]?
what is your map/baro readings[barometric pressure is figured out by the pcm using the map sensor]?
what is fuel pressure/volume[you can have pressure but not enough
volume]?
how does the car run over all[power/no power/sluggish,etc]?
just some thoughts.
The O2 readings seem to be the only thing that is way outta wack.
Fuel pressure and volume seem to be fine. The computer has to be telling the injectors to add more cause before the problem the duty cycle of the injectors was 3% at idle and now they are like 6-7% at idle.
I The MAP and MAF readings are right near where they used to be before the problem and very comparable to a buddys car with the similar setup.
The car runs fine under load. It will blow the tires off in 2nd and 3rd just like normal. No power drop or excess surging. It will, every once in a while, rev up to 1,500 RPM and slowly come back down, but the problem is mostly evident at idle.
Thread Starter
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by Bill Curlee
Rich
Use the tech II to make sure that all of the sensors are working correctly! Especially the temp sensors. if the engine thinks it is very cold out, it will add fuel.
BC
Use the tech II to make sure that all of the sensors are working correctly! Especially the temp sensors. if the engine thinks it is very cold out, it will add fuel.
BC
Thanks Bill, your input is ALWAYS appreciated.
Drifting
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From: bloomfield nj
Originally Posted by RichieRichZ06
I double, tripple and quadrupple checked the vacuum leak idea with a can of propane.
The O2 readings seem to be the only thing that is way outta wack.
Fuel pressure and volume seem to be fine. The computer has to be telling the injectors to add more cause before the problem the duty cycle of the injectors was 3% at idle and now they are like 6-7% at idle.
I The MAP and MAF readings are right near where they used to be before the problem and very comparable to a buddys car with the similar setup.
The car runs fine under load. It will blow the tires off in 2nd and 3rd just like normal. No power drop or excess surging. It will, every once in a while, rev up to 1,500 RPM and slowly come back down, but the problem is mostly evident at idle.
The O2 readings seem to be the only thing that is way outta wack.
Fuel pressure and volume seem to be fine. The computer has to be telling the injectors to add more cause before the problem the duty cycle of the injectors was 3% at idle and now they are like 6-7% at idle.
I The MAP and MAF readings are right near where they used to be before the problem and very comparable to a buddys car with the similar setup.
The car runs fine under load. It will blow the tires off in 2nd and 3rd just like normal. No power drop or excess surging. It will, every once in a while, rev up to 1,500 RPM and slowly come back down, but the problem is mostly evident at idle.
what are the o2 #'s???? how much air is the maf seeing??? also with the car cold,what are the coolant temp and intake temp #'s? they should be very close together with the key on,engine off.
Thread Starter
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by dpd
what are the o2 #'s???? how much air is the maf seeing??? also with the car cold,what are the coolant temp and intake temp #'s? they should be very close together with the key on,engine off.
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From: Slave to the evil empire
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St. Jude Donor '04
Originally Posted by RichieRichZ06
I have a bunch of people off in the shop today that are sick with the flu. It will probably be next week before I can get the numbers off the Tech II. Last time I looked, they were almost the same when the car had sat all night and was nice and cold. When my buddy was looking over it with HP tuners, all the readings were right in line with snapshots that were taken before the problem except for the fuel trims. We never looked at the actual voltage from the O2's, but I will when I can get it back into here again.
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by FFR-Z06
The voltages on the front O2s should be cycling from around 200mV to around 800mV while the car is idling.
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by vettenuts
Is it idle only? That may be why its not setting a code, I think the TPS has to have some throttle for the code to set.