Got a problem with the LM4 (5.3) in the '39 Chevy. After the engine gets to operating temp sometimes it sort of surges. Only notice it at idle, otherwise seems to run smooth. Took compression on #8 and it was fine but temp of the header is about 50 degrees less( 205 vs 260) than the rest. Should I look to the injector? Swap the injectors 2 and 8 around and see if the low heat follows? Any ideas?

 

Swap injectors and then coil packs. Good find with the heat gun

 

Didn't think of the coil pack...thanks.

 

Swapped coils and still low heat on #8 so I've eliminated that. Injectors next or coil wires.

 

Is this a new problem?

 

Clogged #8 injector? Just injecting enough to barely fire... maybe...

 

Maybe some more info. A datalog? More info about the build....

 

Bad news, swapped #2 and #8 injectors and number 8 stayed the same. This is a bone stock 2003 Trailblazer takeout along with the trans. I think this problem may have been there all along but can't prove it. What else would cause just one cylinder to run 50 degrees cooler than the rest? Sorry, don't know how to datalog. As a side note there is a strange whistling sound just before it shifts. I've tried to track it down with no joy. New intake gaskets and can't fine a vacuum leak. The whistle will only happen under load when the RPM goes up just before the shift. Related???

 

A cracked manifold that only shows after it's torqued?