miss, or something else? help please
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 824
Likes: 0
From: Philly Pa
miss, or something else? help please
Hello all , I am a proud new owner of a 03 zo6 with 15k on her .
The other night I'm leaving work jump on the the highway going along punch it to about 120 or so and let off in gear couple seconds later car starts to shutter. No cel no nothing,I get to my house and shut it down . Wake up start the car slight backfire and it stutters when I give it gas. Drive it to my friends shop and he hooked it up to his scanner and ran it in diagnostic mode. Here's the confusing part , car comes up clean. No codes ever and all perimeters are good. So now I'm stumped , he seems to think its a cracked harmonic balancer or a cracked flywheel.
Any ideas or suggestions are appreciated.
Car has 15k miles, unknown h/c ,unknown aftermarket clutch and flywheel ,msd coils and wires , fast 78 , vararam, 3.90 rear I am the second owner and the first was 74 years old and it was kept in a garage with a trickle charger. Was dyno tuned at cartec and all work was done at Corvette paramedics
The other night I'm leaving work jump on the the highway going along punch it to about 120 or so and let off in gear couple seconds later car starts to shutter. No cel no nothing,I get to my house and shut it down . Wake up start the car slight backfire and it stutters when I give it gas. Drive it to my friends shop and he hooked it up to his scanner and ran it in diagnostic mode. Here's the confusing part , car comes up clean. No codes ever and all perimeters are good. So now I'm stumped , he seems to think its a cracked harmonic balancer or a cracked flywheel.
Any ideas or suggestions are appreciated.
Car has 15k miles, unknown h/c ,unknown aftermarket clutch and flywheel ,msd coils and wires , fast 78 , vararam, 3.90 rear I am the second owner and the first was 74 years old and it was kept in a garage with a trickle charger. Was dyno tuned at cartec and all work was done at Corvette paramedics
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 824
Likes: 0
From: Philly Pa
I dunno gonna hook up a vacuum gauge this weekend see what that tells me. I figured the flywheel guess was off also . Valve springs have been replaced I'm pretty sure and the injectors are new also.
Burning Brakes
Joined: Mar 2010
Posts: 1,189
Likes: 4
From: Freeport, FL
Wow, people still use vacuum gauges to diagnois engines (jesting)Sounds like a good plan. Maybe a compression check too.
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Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Sounds like a valve /spring issue. Measure the temp of the intake manifold right at the area where it meets the head with the engine running. If one or more are hotter than the others, that/those valve are remaining open. (use a laser/inferred thermometer.
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 824
Likes: 0
From: Philly Pa
Some good advice there, Thanks chief
Instructor
Joined: Oct 2008
Posts: 212
Likes: 1
From: Clearwater FL
St. Jude Donor '11
Bad wire or wire connection or cracked coil. Check these easy things first. I had a sim prob on a Z06 and thats what it turned out to be, one wire bad, no codes just ran like poop intermittent.
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 824
Likes: 0
From: Philly Pa
Well after three different techs this is what I have.
Tech 1 : ran on. Snap on varis all perimeters fine no misfire codes. Conclusion harmonic balancer or cracked flywheel
Tech 2: ran snap on scanner modus. All perimeters fine. No codes, found vacuum hose not secure on intake.
Conclusion head related problem.
Tech 3
Ran on some kinda scanner at his shop I was told car is stuck in open loop and he pulled a coil and it did not have a misfire code it only said the coil was unplugged.
So I'm thinking about taking the car to Corvette paramedics or ECS.
Tech 1 : ran on. Snap on varis all perimeters fine no misfire codes. Conclusion harmonic balancer or cracked flywheel
Tech 2: ran snap on scanner modus. All perimeters fine. No codes, found vacuum hose not secure on intake.
Conclusion head related problem.
Tech 3
Ran on some kinda scanner at his shop I was told car is stuck in open loop and he pulled a coil and it did not have a misfire code it only said the coil was unplugged.
So I'm thinking about taking the car to Corvette paramedics or ECS.
Pro
Joined: Aug 2010
Posts: 545
Likes: 4
From: Calgary Alberta
Wouldn't hurt to try. See if RPM's change or engine runs smoother or rougher. Reason I say this is the car is 7 plus years old with low mileage. This means it sat idle for quite a bit of it's life. I've seen injectors stick in those situations. Causes exactly the symptoms you describe. The engine computer can monitor the coil circuit to determine if it is present in the circuit of if it fires. Also knock sensors can pickup preignition. The computer fires the injector but has no way to now if fuel or the expected amount of fuel was sprayed. It's only feedback is the oxygen sensors. You say no check engine light, does the CEL come on when you turn the key to start the car?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Well after three different techs this is what I have.
Tech 1 : ran on. Snap on varis all perimeters fine no misfire codes. Conclusion harmonic balancer or cracked flywheel
Tech 2: ran snap on scanner modus. All perimeters fine. No codes, found vacuum hose not secure on intake.
Conclusion head related problem.
Tech 3
Ran on some kinda scanner at his shop I was told car is stuck in open loop and he pulled a coil and it did not have a misfire code it only said the coil was unplugged.
So I'm thinking about taking the car to Corvette paramedics or ECS.
Tech 1 : ran on. Snap on varis all perimeters fine no misfire codes. Conclusion harmonic balancer or cracked flywheel
Tech 2: ran snap on scanner modus. All perimeters fine. No codes, found vacuum hose not secure on intake.
Conclusion head related problem.
Tech 3
Ran on some kinda scanner at his shop I was told car is stuck in open loop and he pulled a coil and it did not have a misfire code it only said the coil was unplugged.
So I'm thinking about taking the car to Corvette paramedics or ECS.
Tech 1 needs a new job! Like Walmart Greeter!!
Coule still be a valve spring issue...
Becareful where you take your car for repairs.
Last edited by Bill Curlee; Oct 28, 2010 at 07:00 PM.