Misfire

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Feb 18, 2008 | 01:04 AM

Quickshift_C5

Thread Starter

Melting Slicks

Joined: Sep 2006

Posts: 2,728

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From: Iowa

Misfire

Can anyone tell me what a misfire sounds like/acts like?

I've tried looking up videos from Youtube and similar places but can't really find a good video to hear what a misfire really sounds like. Plus, from what I read, it can range from a slight vibration to an audible noise.

Feb 18, 2008 | 06:45 AM

BlackZ06

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From: San Rafael CA

You already said it .... it can range from a slight vibration to an audible noise ..... depends on how many cylinders are misfiring, and how often. The PCM will post a P0300 DTC when it detects a misfire .... have you checked for that ???

Feb 18, 2008 | 07:14 AM

dougbfresh

Le Mans Master

Joined: Nov 2005

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They happen all the time and you never know it. There are an amount of misfires that are acceptable (and you can see them on a scanner). When they pass this threshold it's logged in the ECM, 2 in a run cycle and the CEL light is set. P0300 for random misfire and/or P030X where X is the cylinder misfiring.

Last edited by dougbfresh; Feb 18, 2008 at 03:08 PM.

Feb 18, 2008 | 10:56 AM

Quickshift_C5

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Melting Slicks

Joined: Sep 2006

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From: Iowa

Hmm...

You guys notice any misfires in my video?

http://www.youtube.com/watch?v=gMIoB4LCNA8

There is a sharp POP! when I let off the gas, but otherwise it's ok I suppose.

...just trying to narrow down a ticking noise I've been hearing for a while on what it could be.

Feb 18, 2008 | 11:46 AM

jedblanks

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Joined: Dec 2004

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From: Santa Fe TX

If you have the stock Hpipe, pop is normal. If you have it tuned, it will lessen.

my ticking is much louder than yours, but then I have a 228/232 cam.

Feb 18, 2008 | 12:02 PM

Brandon619

Le Mans Master

Joined: Dec 2003

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From: San Diego

Hey quickshift what are the codes your PCM giving? As doug and Black where saying start with the code and then go from there.

Last edited by Brandon619; Feb 18, 2008 at 09:19 PM.

Feb 18, 2008 | 08:56 PM

Quickshift_C5

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Melting Slicks

Joined: Sep 2006

Posts: 2,728

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From: Iowa

Quote:

Originally Posted by Brandon619

Hey quickshift what are the codes your PCM giving? As doug and Black where saying strat with the code and then go from there.

I don't think it has any codes at all. I'll double check when I get home later this week.

Feb 19, 2008 | 02:18 PM

Bill Curlee

Tech Contributor

Joined: Dec 1999

Posts: 32,910

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From: Anthony TX

CI 6,7,8,9,11 Vet

St. Jude Donor '08

Using the C5 Diagnostics, the P-0030 DTC will only post under an excessive misfire situation. During that misfire situation, the Check Engine Light (CEL) will FLASH during the event.
To see what a TRUE misfire is, just unhook one spark plug wire from the spark plug and take her for a spin around the block!

Yep, that will be a misfire and you will see the flashing CEL and the set P-0300 DTC. The DTC will only stay set in memory until you turn the ignition OFF. Once it is off,,,,it resets it self until the next misfire event. It wont hurt anything for a short experiment. Once the car cools off, reinstall the wire.

The popping in the exhaust is normal on our engines!

Bill