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Tuning / Diagnostics -- engine and transmission Tune and diagnostics for engines and auto transmission.

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Old 08-28-2012, 11:08 PM   #1
kstormoen
 
Drives: Camaro SS2 L99
Join Date: Jul 2009
Location: Elk River, MN
Posts: 46
Misfire - need help

I need help figuring this one out. When I start the car up after sitting for the night the car has a slight miss on light acceleration. It goes away after about .5 miles and then the car runs fine. It doesn't happen all the time, but it does happen most of the time. I noticed shortly after I installed LT Headers by dynamax. Here are my mods
Whipple
Rotofab CAI
Dynamax off road LT (No Cats)
vmax ported tb.
jannetty Tune

Here is what I have done to diagnose.

Talked to ted about the miss. He had me datalog, found out cylinder 2 & 8 had a misfire. We determined it isn't in the tune and must be mechanical.

changed plug wires, cleaned CAI, clean MAF - no change, same cylinders are misfiring.

Changed Plugs, did compression test & Leak down test, and check whipple for vac leaks - Plugs looked black so I changed them and it still has a miss. I haven't datalogged to see if it is same 2 cylinders, but I'm sure it is.

Mechanic said that my headers are hitting the floor boards because he could hear it??? any help would be awesome.

Thanks
Keith
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Old 08-29-2012, 06:26 AM   #2
MA2010SS
 
Drives: 2010 Camaro SS
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Location: Somerset MA
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Double check the plug wires, make sure they are seated properly, check resistance accross all plug wires make sure they are all close to the same resistance, take coils #2 and #8 and move those coils to another cylinder data log again and see if the misfire follows the coils or if the misfire is still occuring within those cylinders
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Old 08-29-2012, 08:48 AM   #3
kstormoen
 
Drives: Camaro SS2 L99
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Location: Elk River, MN
Posts: 46
ok, thanks. I will report the results. Thanks ma2010ss

Keith
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Old 03-06-2013, 07:53 AM   #4
zero260asap
 
Drives: 2010 Camaro SS
Join Date: Feb 2012
Location: Clifton Park NY
Posts: 5
2010 1SS I had a misfire on cold startup that would throw the checkengine and service stabilitrac. it lasted about 20 seconds then the car would run fine and the lights would go off. dealer said to do a fuel injection cleaning so i did (knew that wouldn't work it has 25 k on it lol) I've brought it back twice since then, and just got a call today GM gave the go ahead to replace the head because of valve grinds that could cause sticking on start up.
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Old 03-06-2013, 09:16 AM   #5
JANNETTYRACING
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Quote:
Originally Posted by kstormoen View Post
I need help figuring this one out. When I start the car up after sitting for the night the car has a slight miss on light acceleration. It goes away after about .5 miles and then the car runs fine. It doesn't happen all the time, but it does happen most of the time. I noticed shortly after I installed LT Headers by dynamax. Here are my mods
Whipple
Rotofab CAI
Dynamax off road LT (No Cats)
vmax ported tb.
jannetty Tune

Here is what I have done to diagnose.

Talked to ted about the miss. He had me datalog, found out cylinder 2 & 8 had a misfire. We determined it isn't in the tune and must be mechanical.

changed plug wires, cleaned CAI, clean MAF - no change, same cylinders are misfiring.

Changed Plugs, did compression test & Leak down test, and check whipple for vac leaks - Plugs looked black so I changed them and it still has a miss. I haven't datalogged to see if it is same 2 cylinders, but I'm sure it is.

Mechanic said that my headers are hitting the floor boards because he could hear it??? any help would be awesome.

Thanks
Keith
Quote:
Originally Posted by MA2010SS View Post
Double check the plug wires, make sure they are seated properly, check resistance accross all plug wires make sure they are all close to the same resistance, take coils #2 and #8 and move those coils to another cylinder data log again and see if the misfire follows the coils or if the misfire is still occuring within those cylinders
Great Advice,
Also a Leak down test and compression test will rule out any engine mechanical issues that may be hiding behind a warmed up engine.

The only thing left after that would be injectors, or dirt in the injector screens.

I can raise the misfire threasholds in the tune but that would only cover up the problem which we don't want to do.

Ted.
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Old 03-06-2013, 03:10 PM   #6
zero260asap
 
Drives: 2010 Camaro SS
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Location: Clifton Park NY
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Yep the valves on driver side were sticking they said even one of the valve springs was cracked because of it.
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