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Misfire Counts

mswozniak

By mswozniak
in Ask A GM Technician

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mswozniak Enthusiast

mswozniak

Posted
Posted

This is the second time for No. 4 to set a light for misfire counts. It did it about 15,000 miles ago. I changed the plug and wire as a quick fix and that worked for about 15K but I'm concerned that it came back to the same cyl even though it has been about 15,000 miles. Is there something I should be looking for other then ignition problems such as an injector but this is TBI. Any suggestions?

Import Hater Enthusiast

Import Hater

Posted
Posted

Throttle body injection? I think you have the Central Port Injection "Vortec" motor. While the actual fuel injector resembles a throttle body injector, where the fuel actualy sprays out is from a poppet valve. And there's a little tube with a poppet valve going to each intake port. If you were to see the injector assembly, you'd see why it's sometimes known as a "spider" injector. Since you have eight cylinders, it very much resembles one.

 

Providing it isn't an ignition system issue, you could have a problem with the poppet valve for the #4 cylinder. I'd rule out ignition problems first though. The CPI injector isn't even remotely cheap if I remember right.

atboley Enthusiast

atboley

Posted
Posted

for california the injectors are coverd under warranty for 10 yrs or 200000 miles... if your here in cali, take it to the dealer... its probably the injector, especially if they have never been replaced... and yah, its not throttlebody injection...

blue-ss-camaro Enthusiast

blue-ss-camaro

Posted
Posted

I am assumeing you have the old body style seeing how you have a 5.7 in it . I had the same problem try unpluging the egr valve thats what mine was. it will set a light but if it doesnt do it anymore then you will know what it is. I tried everything from injector to plugs and wire to cap and rotor. ended up being the egr. what happens is it will open to early and make the lean condition and thats what sets your light. trust me injectors are a PITA on these trucks. good luck .

mswozniak Enthusiast

mswozniak

Posted
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Posted
Throttle body injection? I think you have the Central Port Injection "Vortec" motor. While the actual fuel injector resembles a throttle body injector, where the fuel actualy sprays out is from a poppet valve. And there's a little tube with a poppet valve going to each intake port. If you were to see the injector assembly, you'd see why it's sometimes known as a "spider" injector. Since you have eight cylinders, it very much resembles one.

 

Providing it isn't an ignition system issue, you could have a problem with the poppet valve for the #4 cylinder. I'd rule out ignition problems first though. The CPI injector isn't even remotely cheap if I remember right.

You're right it's the CPI. I have the Vortec V-6 in another vehicle with CPI. I should have known better.

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