[Z06] Need some help: loss of power
08-24-2013, 09:48 PM
#1
Advanced
Thread Starter
Need some help: loss of power
Hi guys,
I have a 2008 Z06, completely stock, has about 14.4k with Michelin PS2s which have about 2500 miles on them. Love the car, runs real smooth, doesn't use oil, etc. Anyway, I've noticed the car doesn't really seem to have too much power below 2500rpm. A few weeks ago, while making a quick left hand turn, I almost was hit by oncoming traffic because the car did not accelerate ferociously from a dead stop. I knew traffic was coming, and I released the clutch in a quick, but fluid motion at about 1500rpm and fed it about 20% throttle, the car slowly accelerated and started quickly building up speed once I got past about 30mph. It almost felt as though I had started out in second gear, but I know it was actually first gear. I didn't really think anything of it until I was faced with a similar situation recently and slowly accelerated again.
To cut a long story short, what is happening is I can be going 10mph in first gear, hold it at that speed and jam my foot to the floor, and the car will quickly accelerate forward, but not the way a 500hp vehicle should, the same thing will also happen at 20mph. My dad's 1995 LT1 feels faster off the line than my Z06. I would expect the z06 to violently lose control any time you put it to the floor in first or second. It does however, pull quite nicely above 4500rpm. I thought perhaps traction control was saving my butt, knowing it's pretty sensitive (which is good as you get used to a powerhouse like the Z06), so I held the AH button down for 5 seconds to disable all of the techno gadgets, and observed the same exact results, the tires do not even chirp at all. The only way the tires will spin is to aggressively feed it throttle above 35-40mph in first gear. It's almost as if the car is just going
According to the manual, the air filter needs to be changed at 50,000 miles, but I took it out and blew it out with the leaf blower, even though it was pretty clean, and observed no improvement. One thing I have noticed is, the car has considerably more power below 2500rpm when cold, IE on startup in the morning.
Any ideas? Is what I'm experiencing normal for the Z06?
Thanks
-Kevin
I have a 2008 Z06, completely stock, has about 14.4k with Michelin PS2s which have about 2500 miles on them. Love the car, runs real smooth, doesn't use oil, etc. Anyway, I've noticed the car doesn't really seem to have too much power below 2500rpm. A few weeks ago, while making a quick left hand turn, I almost was hit by oncoming traffic because the car did not accelerate ferociously from a dead stop. I knew traffic was coming, and I released the clutch in a quick, but fluid motion at about 1500rpm and fed it about 20% throttle, the car slowly accelerated and started quickly building up speed once I got past about 30mph. It almost felt as though I had started out in second gear, but I know it was actually first gear. I didn't really think anything of it until I was faced with a similar situation recently and slowly accelerated again.
To cut a long story short, what is happening is I can be going 10mph in first gear, hold it at that speed and jam my foot to the floor, and the car will quickly accelerate forward, but not the way a 500hp vehicle should, the same thing will also happen at 20mph. My dad's 1995 LT1 feels faster off the line than my Z06. I would expect the z06 to violently lose control any time you put it to the floor in first or second. It does however, pull quite nicely above 4500rpm. I thought perhaps traction control was saving my butt, knowing it's pretty sensitive (which is good as you get used to a powerhouse like the Z06), so I held the AH button down for 5 seconds to disable all of the techno gadgets, and observed the same exact results, the tires do not even chirp at all. The only way the tires will spin is to aggressively feed it throttle above 35-40mph in first gear. It's almost as if the car is just going
According to the manual, the air filter needs to be changed at 50,000 miles, but I took it out and blew it out with the leaf blower, even though it was pretty clean, and observed no improvement. One thing I have noticed is, the car has considerably more power below 2500rpm when cold, IE on startup in the morning.
Any ideas? Is what I'm experiencing normal for the Z06?
Thanks
-Kevin
Last edited by Circuit Doctor; 08-24-2013 at 09:56 PM.
08-24-2013, 09:53 PM
#2
Burning Brakes
I had a similar type of problem - and the knock sensor harness had been fried by the exhaust manifold on the right hand side.
the harness was in its factory position.
long story short - it was shorting out - making the computer think that the engine was knocking- and the car responded by retarding the timing. result - no low rpm power.
i went thru an air filter and 2 MAF sensors getting there, wound up throwing in the towel and having it towed to dealer who found the problem in 10seconds. (apparently it happens....)
the harness was in its factory position.
long story short - it was shorting out - making the computer think that the engine was knocking- and the car responded by retarding the timing. result - no low rpm power.
i went thru an air filter and 2 MAF sensors getting there, wound up throwing in the towel and having it towed to dealer who found the problem in 10seconds. (apparently it happens....)
Last edited by jmagilto; 08-24-2013 at 09:56 PM.
08-24-2013, 10:16 PM
#3
Advanced
Thread Starter
Jerry,
Thanks so much for your quick reply. Seems like a good theory. Funny you mentioned MAF, I was suspicious of that too, so I actually used MAF cleaner on it when I removed the air filter. My only question is, would a knock sensor circuit short throw a code? I have a scanner, so I suppose I could take a look and see if there are any pending DTCs. I'll take a look at the Chevy shop manual too to see what it says about knock sensors.
What I can also do is take an oscilloscope home from work and look at the MAF signal as well.
Thanks so much for your quick reply. Seems like a good theory. Funny you mentioned MAF, I was suspicious of that too, so I actually used MAF cleaner on it when I removed the air filter. My only question is, would a knock sensor circuit short throw a code? I have a scanner, so I suppose I could take a look and see if there are any pending DTCs. I'll take a look at the Chevy shop manual too to see what it says about knock sensors.
What I can also do is take an oscilloscope home from work and look at the MAF signal as well.
08-24-2013, 10:40 PM
#4
If you scanner will datalog the OBDII data you can look at your timing real time (or store it and review it). I think there's a datapoint for the knock retard function as well (how much timing it is pulling if it is indeed sensing knock, or thinking that it is sensing knock).
If your scanner won't do that, then you can get a Chinese ELM327 bluetooth OBDII adapter for $15 off of ePray or Amazon that will let you datalog to your smartphone with an Android app called "Torque". No kidding
If your scanner won't do that, then you can get a Chinese ELM327 bluetooth OBDII adapter for $15 off of ePray or Amazon that will let you datalog to your smartphone with an Android app called "Torque". No kidding
08-25-2013, 11:06 AM
#6
Burning Brakes
If you scanner will datalog the OBDII data you can look at your timing real time (or store it and review it). I think there's a datapoint for the knock retard function as well (how much timing it is pulling if it is indeed sensing knock, or thinking that it is sensing knock).
If your scanner won't do that, then you can get a Chinese ELM327 bluetooth OBDII adapter for $15 off of ePray or Amazon that will let you datalog to your smartphone with an Android app called "Torque". No kidding
If your scanner won't do that, then you can get a Chinese ELM327 bluetooth OBDII adapter for $15 off of ePray or Amazon that will let you datalog to your smartphone with an Android app called "Torque". No kidding
thanks!
08-25-2013, 07:59 PM
#7
Advanced
Thread Starter
Hi everyone,
I scanned it today and saw no codes, nor any pending codes. My scan tool shows live data. I can look at degrees of advance, but I cannot monitor knock retard. The fuel system will go into open loop if you jab the throttle to the floor in neutral, so the TPS is working. When driving to work this morning, I positioned myself on a wide, desolate street with no one around. With all traction and active handling disabled, I got up to 10mph in first, held it there and then nailed my foot to the floor. No wheelspin, no explosion forward, just unremarkable acceleration. Repeated the same test at 20mph, almost no wheelspin, again, unremarkable acceleration. Repeated same test at 30mph, and held my foot on the floor, very little wheelspin, and some decent acceleration. At no point during any of those tests did the back end feel like it wanted to kick out. What was interesting is in all 3 cases, you could almost hear the engine bogging.
After that, I got onto a nearby road, and accelerated to 60mph in second, turned all traction control on, and floored it and held it to the floor until about 75-80. No explosive acceleration, no "traction system active" message, no wheelspin.
Something has got to be really screwed up on this thing. Low fuel pressure perhaps? Bad spark? Any ideas? I know the PS2s are a great tire, but I should have no problem overcoming their traction limits in first or second gear. I don't drive this thing every day, so I certainly haven't "gotten used to" how fast it is.
Thanks
-Kevin:
I scanned it today and saw no codes, nor any pending codes. My scan tool shows live data. I can look at degrees of advance, but I cannot monitor knock retard. The fuel system will go into open loop if you jab the throttle to the floor in neutral, so the TPS is working. When driving to work this morning, I positioned myself on a wide, desolate street with no one around. With all traction and active handling disabled, I got up to 10mph in first, held it there and then nailed my foot to the floor. No wheelspin, no explosion forward, just unremarkable acceleration. Repeated the same test at 20mph, almost no wheelspin, again, unremarkable acceleration. Repeated same test at 30mph, and held my foot on the floor, very little wheelspin, and some decent acceleration. At no point during any of those tests did the back end feel like it wanted to kick out. What was interesting is in all 3 cases, you could almost hear the engine bogging.
After that, I got onto a nearby road, and accelerated to 60mph in second, turned all traction control on, and floored it and held it to the floor until about 75-80. No explosive acceleration, no "traction system active" message, no wheelspin.
Something has got to be really screwed up on this thing. Low fuel pressure perhaps? Bad spark? Any ideas? I know the PS2s are a great tire, but I should have no problem overcoming their traction limits in first or second gear. I don't drive this thing every day, so I certainly haven't "gotten used to" how fast it is.
Thanks
-Kevin
:
Last edited by Circuit Doctor; 08-25-2013 at 08:07 PM.
08-25-2013, 08:09 PM
#8
Man, I dunno. If it's getting spark advance and fuel it should go, like, fast. Only thing I could advise is getting it on a dyno with a good tuner... the ECM/PCM could be holding things back for some reason (there are all kinds of things going on, torque management, fuel enrichment, etc, that could cause the computer to hold the engine back if it thinks something is out of line). Only way to nail it down quickly is to get it on a dyno with equipment that can datalog everything, and of course someone that understands it all (not me 
).
).
08-25-2013, 08:48 PM
#9
Safety Car
Paying a dealer to diagnose the problem for the normal $100-200 seems like a vastly better course of action than guessing or having someone diagnose from a long distance.
A dyno certainly will help but likely will cost what a real GM Tech 2 diagnosis will cost and likely yield less information.
A very easy data point you can give us is to compare the spool up in the motor at wot in first to you opening the TB butterflys by hand with the car stopped and in neutral. Does it still take its sweet time gaining revs or is it near instantaneous as it should be.
On your logging. Does the throttle position hit 100% immediately as you hit the throttle?
A dyno certainly will help but likely will cost what a real GM Tech 2 diagnosis will cost and likely yield less information.
A very easy data point you can give us is to compare the spool up in the motor at wot in first to you opening the TB butterflys by hand with the car stopped and in neutral. Does it still take its sweet time gaining revs or is it near instantaneous as it should be.
On your logging. Does the throttle position hit 100% immediately as you hit the throttle?
Last edited by pkincy; 08-25-2013 at 08:51 PM.
08-25-2013, 09:16 PM
#11
Advanced
Thread Starter
Paying a dealer to diagnose the problem for the normal $100-200 seems like a vastly better course of action than guessing or having someone diagnose from a long distance.
A dyno certainly will help but likely will cost what a real GM Tech 2 diagnosis will cost and likely yield less information.
A very easy data point you can give us is to compare the spool up in the motor at wot in first to you opening the TB butterflys by hand with the car stopped and in neutral. Does it still take its sweet time gaining revs or is it near instantaneous as it should be.
On your logging. Does the throttle position hit 100% immediately as you hit the throttle?
A dyno certainly will help but likely will cost what a real GM Tech 2 diagnosis will cost and likely yield less information.
A very easy data point you can give us is to compare the spool up in the motor at wot in first to you opening the TB butterflys by hand with the car stopped and in neutral. Does it still take its sweet time gaining revs or is it near instantaneous as it should be.
On your logging. Does the throttle position hit 100% immediately as you hit the throttle?
I remember the first time I drove this car to work a year ago when it had 7,000 miles on it, I went to pass someone in second gear at around 35mph. As I was changing lanes, I jabbed the throttle (surely not to the floor), and I almost lost control of the car with traction and active handling left on, it fishtailed all over the place. The temperature then versus now is comparable. It's been about 75 degrees lately, roughly the same temperature it was when I bought the car.
Something must be really screwed up. It's a fast car, and still hauls the mail, but if I can floor it at any speed in first or second without TC or AH intervening, something must not be right. Agreed? Perhaps a quick youtube video is in order.
Last edited by Circuit Doctor; 08-25-2013 at 09:19 PM.
08-25-2013, 09:19 PM
#12
Race Director
the throttle response s/b instantaneous...obviously something is not right.
Consider Corvettes of Weschester (in Ossining), a supporting CF vendor, to help you with this.
There also may be other CF vendors who specialize in Corvettes that are local to you.
Consider Corvettes of Weschester (in Ossining), a supporting CF vendor, to help you with this.
There also may be other CF vendors who specialize in Corvettes that are local to you.
Last edited by Gary '09 C6; 08-25-2013 at 09:22 PM. Reason: sp
08-25-2013, 09:24 PM
#13
[...] What's interesting is, at about 65mph in 6th gear, if you lift off the gas, the ignition advance goes out to 41 degrees, which seems ludicrous. If you floor it in 6th at 65, presenting a huge load to the power train, the ignition advance went to something like 5 degrees, which seems equally stupid. [...]
08-26-2013, 01:03 AM
#14
Follow these simple steps:
1) locate a trusted LS shop in your area
2) call and make an appointment for some dyno pulls and data logging.
3) show up to your appointment and see what she puts down as well as your fuel and spark tables.
If anything is out of the norm, the shop should be able to detect it and address the issue.
Done.
1) locate a trusted LS shop in your area
2) call and make an appointment for some dyno pulls and data logging.
3) show up to your appointment and see what she puts down as well as your fuel and spark tables.
If anything is out of the norm, the shop should be able to detect it and address the issue.
Done.
08-26-2013, 02:13 AM
#15
Burning Brakes
CircuitDoctor:
I have a 2008 Z06 (Certified Preowned with only 7000 miles now) and I have the EXACT same feeling, and I actually posted a thread about it a while ago.
I had it dyno'd at West Coast Corvettes and the dyno curve was normal. max was around 450 hp / 450 lb-ft. So I still don't know if my car is normal or not.
When I stab the throttle pedal to the floor when I'm in first or second gear, it simply doesn't respond the way I think a Z06 should respond. It kinda bogs for a while before I'll get a little bit of silent wheel spin. But once I'm moving briskly at at 4500+ rpm, it does have the torque feel that I expect.
I'm tempted to take it to a Chevy Dealer service department nearby that is respected (Connell Chevrolet) , given that I paid the premium for a CPO car with 12 months bumper to bumper and an extra 3 years GMPP, but I've also been advised by others on this forum that the benefit of the GMPP is for engine replacement in catastrophic failure, and that I should stick with a trusted independent corvette mechanic (e.g. Charlie at RPM) for anything else.
I have a 2008 Z06 (Certified Preowned with only 7000 miles now) and I have the EXACT same feeling, and I actually posted a thread about it a while ago.
I had it dyno'd at West Coast Corvettes and the dyno curve was normal. max was around 450 hp / 450 lb-ft. So I still don't know if my car is normal or not.
When I stab the throttle pedal to the floor when I'm in first or second gear, it simply doesn't respond the way I think a Z06 should respond. It kinda bogs for a while before I'll get a little bit of silent wheel spin. But once I'm moving briskly at at 4500+ rpm, it does have the torque feel that I expect.
I'm tempted to take it to a Chevy Dealer service department nearby that is respected (Connell Chevrolet) , given that I paid the premium for a CPO car with 12 months bumper to bumper and an extra 3 years GMPP, but I've also been advised by others on this forum that the benefit of the GMPP is for engine replacement in catastrophic failure, and that I should stick with a trusted independent corvette mechanic (e.g. Charlie at RPM) for anything else.
08-26-2013, 09:48 AM
#16
Safety Car
With the Nannies off, it is still slow? Your dyno curve should show the loaded spool up from throttle tip in (normally 2500-3000 rpm on a dyno) but that is in 4th normally.
The fear of a dealer comes from not having a dealer that either cares or knows about Corvettes. It is up to you to find one that thinks differently. Maybe they sponsor Cars and Coffee, or a race car, or several autox cars. Does the owner drive a Cruze or a Corvette?
My dealer sponsored my Race Car, a number of Autox cars and got a new Corvette every 3 months for his company car. Back in the bad head gasket days of the first ZR1, he was where GMPP had the ZR1s engine R&Rd in the shop and pulled apart to replace the head gasket.
Given that it is a GM product, and that GM has a ton of proprietary equipment to work on the car (particularly its complicated systems) if you don't find a good dealer in your area than it is your bad, not theirs.
Both of these cases could be the result of some of the Nannies over operating. That is wild speculation on my part, but if the car is not diagnosed correctly you will never find out what is wrong with it. And going to someone that is really good at installing new heads, cams and suspension parts on lots of Corvettes, is not where I would go to get a diagnosis done.
1st Edit: BTW, my dealer has retired and sold his store so I can't recommend them but Rio Vista is only a partial days drive from Irvine and Abel Chevrolet seems to get nothing but kudos from CF members. If I can't find a highly recommended local dealer from the San Diego Corvette Club guys that is where I would go.
2nd Edit: I will call the NCal dealer when they get in today and see if the mechanic I used is still employed there and if not where he is. That at least can give some of the Nor Cal people another source although that is where Abel Chevrolet is.
Maybe we should start a thread on good Chevrolet Dealers that value Corvette owners.
The fear of a dealer comes from not having a dealer that either cares or knows about Corvettes. It is up to you to find one that thinks differently. Maybe they sponsor Cars and Coffee, or a race car, or several autox cars. Does the owner drive a Cruze or a Corvette?
My dealer sponsored my Race Car, a number of Autox cars and got a new Corvette every 3 months for his company car. Back in the bad head gasket days of the first ZR1, he was where GMPP had the ZR1s engine R&Rd in the shop and pulled apart to replace the head gasket.
Given that it is a GM product, and that GM has a ton of proprietary equipment to work on the car (particularly its complicated systems) if you don't find a good dealer in your area than it is your bad, not theirs.
Both of these cases could be the result of some of the Nannies over operating. That is wild speculation on my part, but if the car is not diagnosed correctly you will never find out what is wrong with it. And going to someone that is really good at installing new heads, cams and suspension parts on lots of Corvettes, is not where I would go to get a diagnosis done.
1st Edit: BTW, my dealer has retired and sold his store so I can't recommend them but Rio Vista is only a partial days drive from Irvine and Abel Chevrolet seems to get nothing but kudos from CF members. If I can't find a highly recommended local dealer from the San Diego Corvette Club guys that is where I would go.
2nd Edit: I will call the NCal dealer when they get in today and see if the mechanic I used is still employed there and if not where he is. That at least can give some of the Nor Cal people another source although that is where Abel Chevrolet is.
Maybe we should start a thread on good Chevrolet Dealers that value Corvette owners.
Last edited by pkincy; 08-26-2013 at 09:56 AM.
08-26-2013, 09:58 AM
#17
Hi Circuit,
Sorry that you are having this trouble with your Z! It does sound like something is wrong, your Z should be taking off on acceleration.
I read through the thread and I am concerned that you keep putting your Z in a situation that she is not comfortable. There is something wrong and I really think you need to go it it diagnosed. I do not have any incite on what the diagnosis is; I am technical. Sorry! If you decide to go the dealership route please let me know so I can assist. Regardless please have it checked out and keep us all posted on the outcome,
Kelly J.
Chevrolet Customer Care
Sorry that you are having this trouble with your Z! It does sound like something is wrong, your Z should be taking off on acceleration.
I read through the thread and I am concerned that you keep putting your Z in a situation that she is not comfortable. There is something wrong and I really think you need to go it it diagnosed. I do not have any incite on what the diagnosis is; I am technical. Sorry! If you decide to go the dealership route please let me know so I can assist. Regardless please have it checked out and keep us all posted on the outcome,
Kelly J.
Chevrolet Customer Care
08-26-2013, 10:04 AM
#18
08-26-2013, 01:28 PM
#19
Burning Brakes
If I decide to go to Abel Chevrolet, is there a specific person (service writer , is it called?) that I should first contact. It would be a 6 hour drive for me and put 800 miles (roundtrip) on a car with only 7,000 miles.
08-26-2013, 01:36 PM
#20
