[Z06] Car is running rough.... help please
Instructor
Joined: Apr 2010
Posts: 234
Likes: 0
From: Lynden Washington
You mention the car is running hot? Or is it? Manual of CF will tell you if 230 is HOT.
If it is hot and you hear a pecking... DOES IT HAVE WATER? Is it the water pump crying for WATER?
Water is good but temp high? Is that thermostat opening? The fans working?
Yes to all? Is the timing on the mark?
I will tell you some of the sensors and swithces are very tempermental.
I new a guy with cold start issues in a late model SUV. He narrowed down to a cold start thermo valve... I came in after his excitment of discovery only to find there was not enough WATER to keep the switch warm enough under cold conditions. He just need water/antifreeze. Some things are very sensitve.
One last thing about a valve... If you looked at a valve spring in lets say good unbroken condition... Would looking at it tell you if a valve was stuck or siezed. If an exhaust valve was stuck would it run hot? Would it run rough.
You want to rule out valves! Put the themometer in it mouth like the doc, compression check it.
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
230* isn't necessarily hot for an LS6 engine being driven in a spirited manner, although many folks will say they never get over 200* in thier car. But then they might never exceed a posted speed limit either. But, if the center section of the front air deflector is missing then your car will run about 15-20* warmer...I know because I did that for a few months.
Does it still sound and act like that now with a cold engine?
The LS6 does sound a bit like a sewing machine and does have a little bit of a lope to it as well so are you sure it isn't normal stuff. Also the clutch is a bit of a chatter box by design (noise goes away when pedal is depressed). I would be curious to know what other symptoms the car is giving you.
Is it full of coolant? Maybe it was run a bit low or needs to be burped.
Any mods that you are aware of?
What happened immediately before the rough idle? Did you miss a shift or overrev the engine at all downshifting? You can bang the rev limited on the way up and not hurt it, but nothing will prevent it from overreving when downshifting or missing a gear.
A trully rough idle should be giving you some telltale signs of trouble. Either codes or basic stuff as already covered by 1REDZED.
Does it still sound and act like that now with a cold engine?
The LS6 does sound a bit like a sewing machine and does have a little bit of a lope to it as well so are you sure it isn't normal stuff. Also the clutch is a bit of a chatter box by design (noise goes away when pedal is depressed). I would be curious to know what other symptoms the car is giving you.
Is it full of coolant? Maybe it was run a bit low or needs to be burped.
Any mods that you are aware of?
What happened immediately before the rough idle? Did you miss a shift or overrev the engine at all downshifting? You can bang the rev limited on the way up and not hurt it, but nothing will prevent it from overreving when downshifting or missing a gear.
A trully rough idle should be giving you some telltale signs of trouble. Either codes or basic stuff as already covered by 1REDZED.
Instructor
Joined: Apr 2006
Posts: 204
Likes: 0
From: Seattle
Red Not to get off topic, but what others have said is good advice, just some caution for maybe some readers to this thread....what the poster described sounded like the valve spring problem these cars can have, I totally agree with Red on how to look at a problem with a motor but not in this case.
these cars break springs way to often, the best and safest is to pop ther valve covers first before doing anything else if your having a miss, or hear ticking at the motor, a valve hanging down into the bore is NOT A GOOD THING!!
stop the motor, check things out, if not a broken spring say a few hail Mary's and move on, then do the normal tests to see whats going on,
your window of just replacing a valve spring and driving off into the sunset is VERY small.....serious motor damage is very easy with a valve hanging during other checks of the motor.
Peace, B.
these cars break springs way to often, the best and safest is to pop ther valve covers first before doing anything else if your having a miss, or hear ticking at the motor, a valve hanging down into the bore is NOT A GOOD THING!!
stop the motor, check things out, if not a broken spring say a few hail Mary's and move on, then do the normal tests to see whats going on,
your window of just replacing a valve spring and driving off into the sunset is VERY small.....serious motor damage is very easy with a valve hanging during other checks of the motor.
Peace, B.
Le Mans Master
Joined: Dec 2005
Posts: 8,580
Likes: 964
From: Communist Colorado
One other thing ASLP... If you set out to do a compression check (having jumped to a valve problem) first. As you pulled each spark plug out, you would then observe the plug. Is it 'normal' in its appearence from burning. Is it soaked with oil? Is it black with soot? is the eletrodes burned worn and gap way off?
Should you ever follow this line of manually checking the cylinders one by one. Use a muffin pan out of moms kitchen. Each muffin compartment will hold one plug numbered 1 thru 8 (in this case of a eight cylinder) But all plugs are compared one to another. If one is very odd/different then that is more than likely where an/the issue is, or in the future will be.
Burned valves aren't seen by a broken spring under a valve cover. But it will be evident in an old school compression check.
AND trust me... If your plugs look good/uniform-that is good news, and good news you need to know.
When you go to a doctor the first thing they do is stick thermometer in you mouth to check how you are inside...
If you suspect valve train stick a thermometer in it mouth.
Valve train, rough idle, but was there a noted loss in power?
Most of all don't stress and don't worry. Us old guys have walked in your shoes. Pissed and frustrated as youth. But the FIX is knowledge that will never be taken away.
And the test I spoke of work on any make of car. Even mama's Subaru!
Should you ever follow this line of manually checking the cylinders one by one. Use a muffin pan out of moms kitchen. Each muffin compartment will hold one plug numbered 1 thru 8 (in this case of a eight cylinder) But all plugs are compared one to another. If one is very odd/different then that is more than likely where an/the issue is, or in the future will be.
Burned valves aren't seen by a broken spring under a valve cover. But it will be evident in an old school compression check.
AND trust me... If your plugs look good/uniform-that is good news, and good news you need to know.
When you go to a doctor the first thing they do is stick thermometer in you mouth to check how you are inside...
If you suspect valve train stick a thermometer in it mouth.
Valve train, rough idle, but was there a noted loss in power?
Most of all don't stress and don't worry. Us old guys have walked in your shoes. Pissed and frustrated as youth. But the FIX is knowledge that will never be taken away.
And the test I spoke of work on any make of car. Even mama's Subaru!
Do a search on the subject. Youll be surprised Im sure. Some guys have gotten lucky and some lost engines. Lotta guys lost a spring at very low rpms or even just pulling into their driveways.
** I guess its worth adding that the belief is that GM had a bad run of springs in the LS6 engines for the most part and in 2002 for the most part, but weve seen 03's loose springs also**
Last edited by 81c3; May 1, 2010 at 12:22 PM.
Melting Slicks
Joined: Aug 2004
Posts: 2,220
Likes: 6
From: www.Z16.org North/West Pennsylvania
Wow, I am new to the forum, and new to my Z06, but I have been around cars for quite some time... First off I am a bit surprised at what seems to me such a quick conclusion over valve springs? If I was really drawn to consider a valve issue, I may run a simple compression test of each cylinder. Seems to me that if there was a valve issue it would be eveident in the needle of the gauge? No reading, wild and fluxuating in comparison to the good cylinders.
I am new I must confess, just seem like so much reliance to DTC's is a bit 'new school for me' Sure if the noise (pecking) was so great I may be afraid to start the car. But if it sounded like a lifter that lost prime, I would check the compression be for I seperated a gasket? I am down right resistant to pulling a valve cover and having to replace a gasket $$ if I don't have to. If that needle on the compression gauge is out lof line, I know exactly where I am going to look when I remove that valve cover?
Lots of things can cause a rough idle. Like the one member suggested, pull a plug wire one at a time, if there is a change? You know exactly where to look.
Hell even plug wires have ohms resistance specs. They too can be measured on by one.
I just find it a bit overwhelming that such drastic conclusions could be jumped to before some of that "old school" math is done?
I had a beautiful Jeep CJ5 many years ago, baddest on the hill. The idle perplexed me after all my checks. I threw my hands up, put it on a scope. The tech looked at me, and I looked at him in return with smiles of concurrance and heads nodding. I fixed the rough idle proble for 99 cents. I was a hairline crack in ONE plug. Yeah, I did pay $65 bucks for the scope, but 99 cents for the repair.
Don't panic, if its bad don't drive it. But be methodical to rule out items one by one.
Ya just bought it? Did ya fill it up at some ****ty station?
Enjoy the challenge of the fix. It's how we learn.
Thats in my own humble opinion.
I am new I must confess, just seem like so much reliance to DTC's is a bit 'new school for me' Sure if the noise (pecking) was so great I may be afraid to start the car. But if it sounded like a lifter that lost prime, I would check the compression be for I seperated a gasket? I am down right resistant to pulling a valve cover and having to replace a gasket $$ if I don't have to. If that needle on the compression gauge is out lof line, I know exactly where I am going to look when I remove that valve cover?
Lots of things can cause a rough idle. Like the one member suggested, pull a plug wire one at a time, if there is a change? You know exactly where to look.
Hell even plug wires have ohms resistance specs. They too can be measured on by one.
I just find it a bit overwhelming that such drastic conclusions could be jumped to before some of that "old school" math is done?
I had a beautiful Jeep CJ5 many years ago, baddest on the hill. The idle perplexed me after all my checks. I threw my hands up, put it on a scope. The tech looked at me, and I looked at him in return with smiles of concurrance and heads nodding. I fixed the rough idle proble for 99 cents. I was a hairline crack in ONE plug. Yeah, I did pay $65 bucks for the scope, but 99 cents for the repair.
Don't panic, if its bad don't drive it. But be methodical to rule out items one by one.
Ya just bought it? Did ya fill it up at some ****ty station?
Enjoy the challenge of the fix. It's how we learn.
Thats in my own humble opinion.
Instructor
Joined: Apr 2010
Posts: 234
Likes: 0
From: Lynden Washington
Thank you for the GOOD information. I am new to the Z06, I too am here to learn. I will keep this all in mind should the situation ever happen to me. I conceed to the information that has been shared regarding a broken valve spring. After all, I too own an '02.
Respectfully- Thank you.
Respectfully- Thank you.
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Burning Brakes
Joined: Aug 2007
Posts: 880
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From: Bath PA
Instructor
Joined: Apr 2010
Posts: 234
Likes: 0
From: Lynden Washington
I am glad you posted your original post, I too have learned a git about the Z.
We are all here for you, just wondering how your doing?
William
3rd Gear
Joined: Nov 2009
Posts: 3
Likes: 0
I am having a similar problem on a 2000 that I have had for a number of years.
First - the 130 oil pressure is due to a bad oil pressure sending unit (aka oil pressure sending switch). This is a common issue - here is a good post for reference.
http://forums.corvetteforum.com/c5-t...y-vectorz.html
Did you ever trace down your issue?
I am getting misfire codes and I recently got a ram air + new plugs/cables. Anybody hear of issues with new plugs + ram air?
First - the 130 oil pressure is due to a bad oil pressure sending unit (aka oil pressure sending switch). This is a common issue - here is a good post for reference.
http://forums.corvetteforum.com/c5-t...y-vectorz.html
Did you ever trace down your issue?
I am getting misfire codes and I recently got a ram air + new plugs/cables. Anybody hear of issues with new plugs + ram air?
Thread Starter
Intermediate
Joined: Apr 2010
Posts: 30
Likes: 0
Thanks everyone for your help I have changed plugs and wires and took off the valve covers and the springs are fine..... it still has a rough idle.... and now a grind going into reverse 
I was told at the stealership that it needs a full rebuild !!! FML I found a guy in town that will change the trannys out if I find a good used one for $300. That sounds like a good deal but I don't know where to find a good used one or whats a fair price any ideas ?
I was told at the stealership that it needs a full rebuild !!! FML I found a guy in town that will change the trannys out if I find a good used one for $300. That sounds like a good deal but I don't know where to find a good used one or whats a fair price any ideas ?
Le Mans Master
Joined: Dec 2005
Posts: 8,580
Likes: 964
From: Communist Colorado
Thanks everyone for your help I have changed plugs and wires and took off the valve covers and the springs are fine..... it still has a rough idle.... and now a grind going into reverse I was told at the stealership that it needs a full rebuild !!! FML I found a guy in town that will change the trannys out if I find a good used one for $300. That sounds like a good deal but I don't know where to find a good used one or whats a fair price any ideas ?
I was told at the stealership that it needs a full rebuild !!! FML I found a guy in town that will change the trannys out if I find a good used one for $300. That sounds like a good deal but I don't know where to find a good used one or whats a fair price any ideas ?
Instructor
Joined: Apr 2010
Posts: 234
Likes: 0
From: Lynden Washington
ASLP about that rough idle... Is the CAI cold air intake/air cleaner all stock?
Do you hear any air hissing under the hood, like a vacumn leak?
Vacumn gage, and compression gage is good money spent at Sears.
What did the old plugs look like? I hope you noted their appearence to the corrosponding holes?
How about that pecking? Is it a peck, loud peck, knock? Is it a tick tick tick?
Do you have oil? Water?
Damn now your going for the gear box?
Keep your cool man.
Do you hear any air hissing under the hood, like a vacumn leak?
Vacumn gage, and compression gage is good money spent at Sears.
What did the old plugs look like? I hope you noted their appearence to the corrosponding holes?
How about that pecking? Is it a peck, loud peck, knock? Is it a tick tick tick?
Do you have oil? Water?
Damn now your going for the gear box?
Keep your cool man.
