Please help with misfire

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May 15, 2024 | 12:29 PM

Fayro

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4th Gear

Joined: May 2024

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Please help with misfire

Hi please I need help with my 2009 Corvette
I have check engine light sometimes flash and traction light on. Check it with scanner I have misfire p0300 and the car only misfire on idle higher rpm nothing even check engine goes , I changed wire, plugs, all the injectors clean it at shop with machine changed MAP SENSOR still the same and the data on scanner shows 4 and 6 misfiring so so I removed The head and checked the valve all good and changed head gasket but the same nothing change so I checked the piston pressure all 180 except cylinder 4 and 6 150 psi could be the piston rings.also checked all wire good
Please if someone can help I appreciate

May 15, 2024 | 12:40 PM

sramzzz

Melting Slicks

Joined: May 2020

Posts: 2,136

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From: North Little Rock, AR

It could be a coil. Trying changing the #4 or 6 out with one that is good and see if the problem follows.

May 15, 2024 | 01:11 PM

Fayro

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4th Gear

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Thanks for the quick reply I did swap the coil and the injectors with the other side and I did vacuum leak test with smoke machine and nothing the same.

May 15, 2024 | 03:10 PM

C5 Diag

Moderator, Tech Contributor

Joined: Sep 2013

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From: Cape Coral, Florida

Even if you changed all those parts you should still check the electrical side of the coil packs (4 wires) and injectors (2 wires)…not knowing your electrical expertise I’ll stop right here…usually idle only misfires are ignition related…why was MAP sensor changed for a misfire ????

Last edited by C5 Diag; May 15, 2024 at 05:32 PM.

May 16, 2024 | 12:26 AM

Fayro

Thread Starter

4th Gear

Joined: May 2024

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I changed a the map sensor because when I unplugged it's run fine and no misfire and no traction control light.i swap the coil and the injectors and checked all the wire 4 for the coil and 2 for the injectors and the same side of the misfire the catalytic converter was broken I removed pieces.
Really thanks

May 16, 2024 | 01:06 AM

Fayro

Thread Starter

4th Gear

Joined: May 2024

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Please one more question is there a way to increase the idle I have autel and launch scanner.

May 16, 2024 | 04:18 AM

C5 Diag

Moderator, Tech Contributor

Joined: Sep 2013

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From: Cape Coral, Florida

Quote:

Originally Posted by Fayro

Please one more question is there a way to increase the idle I have autel and launch scanner.

No !!

May 16, 2024 | 06:08 PM

gdmoore01

Drifting

Joined: Apr 2016

Posts: 1,286

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From: DFW Texas

One other possibility not mentioned is a failing torque tube bearing or rubber coupler. These can send vibrations to the engine that are interpreted as a misfire by the ECU. Are you having or feeling any noises or vibrations that seem located in the middle of the car when driving? That would be something to have checked out to eliminate the possibility.

Good luck...GD