Miss firing

[Swimmer8366]

Cylinder 2 and 7 miss fire causing random miss code. Am I looking at an intake gasket leak?

 

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[GMCustomerService]

Cylinder 2 and 7 miss fire causing random miss code. Am I looking at an intake gasket leak?

 

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Good Evening Swimmer8366,

 

We are sorry to learn of the recent concerns you have been experiencing. We see that you are seeking the input of other forum members, so we would like to offer our assistance as well. Our team would be more than happy to look into your situation on our end. If this is something of interest, please send us over a private message so that we may continue with this process. Thank you and please enjoy the rest of your weekend.

 

Philip J.

GM Customer Care

[jreyes0a39oz]

first thing to do is to do a compression and leak down test have you done it yet?

[Jsdirt]

Just look at your freeze frame data - see what temperature the engine was at when the code set, and what the fuel trims are while it's running. If the code set on a cold engine, and your fuel trims are +10 or higher, and get better as it warms up, it's more than likely an intake gasket. If the trims are going negative, and the misfire is the same hot or cold, there's a good chance it's ignition related. Once all that is ruled out, then proceed with a compression and leak down test.

 

All you need is a spray bottle of water to spray along the mating surface of the head and intake - listen to the engine and watch the trims as you spray. Sometimes you'll even hear the water being sucked in too.

[Swimmer8366]

Haven't really been able to get into it happened this morning way to work been at both jobs all day. I'm thinking it's an intake gasket because it is happening at cold but than again it continues the same through heat up and driving even back fires at times

 

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[Swimmer8366]

Finally got to check the truck out for this miss fire problem. I decided to unplug my mass air flow sensor and run the truck. Once unplugged there are no more miss fires.

 

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[Swimmer8366]

Replaced mass air flow yesterday truck still miss fires going to redo pig tail going to mass air flow.

 

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[Swimmer8366]

Truck does not miss fire like it was do not get codes and only feel it ever once in a while at idle. On very cold days only

 

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[Jsdirt]

Idle, and at cold temperatures, tells me there's probably an intake manifold leak.

 

• High vacuum makes leaks more apparent (idle = high vacuum)
• Cold temperatures make leaks more apparent (cold temps contract metal & plastic - any leaks become larger)

[Swimmer8366]

Ended up doing intake gaskets injectors plugs wires and a fuel pump. Still misfire. Pulled driver side valve cover to check valve springs. Found

 

 

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Idle, and at cold temperatures, tells me there's probably an intake manifold leak.

 

• High vacuum makes leaks more apparent (idle = high vacuum)
• Cold temperatures make leaks more apparent (cold temps contract metal & plastic - any leaks become larger)

Ended up doing intake gaskets injectors plugs wires and a fuel pump. Still misfire. Pulled driver side valve cover to check valve springs. Found

 

 

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[Jsdirt]

Head gasket time.

[Swimmer8366]

Haven't found miss fire problem hoping it's low pressure

 

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[tbarn]

Cylinder head time. Don't waste any more money if you're not going to fix your main problem.