97 Vortec 5.7 Misfiring

[jhend1000]

Hi, I'm new to the forum and to the GMT-400 platform. My truck is currently throwing a multiple cylinder misfire code and is running very poorly. I have already replaced the distributor, cap, rotor, spark plugs, and spark plug wires. I tested the fuel pressure and it's holding 56 PSI both with the key on and engine off and when the engine is running. The engine behaves like it has one (or more) of the poppet injectors cutting in and out intermittently. Is there any way to test the spider injector assembly before I purchase a replacement? Are the AC Delco replacements reliable units? Are there any other common issues that cause this to happen?

[bcrooms]

5 minutes ago, jhend1000 said:

Hi, I'm new to the forum and to the GMT-400 platform. My truck is currently throwing a multiple cylinder misfire code and is running very poorly. I have already replaced the distributor, cap, rotor, spark plugs, and spark plug wires. I tested the fuel pressure and it's holding 56 PSI both with the key on and engine off and when the engine is running. The engine behaves like it has one (or more) of the poppet injectors cutting in and out intermittently. Is there any way to test the spider injector assembly before I purchase a replacement? Are the AC Delco replacements reliable units? Are there any other common issues that cause this to happen?

I'm having the same problem with my 97 5.7L, and a reliable mechanic told me to check the ignition coil.  Sure enough it is cracked and I can see where it has been cross-arcing. I have new parts from ACdelco on hand, just trying to find time to replace it and see if that improves things. 

[jhend1000]

9 minutes ago, bcroomz said:

I'm having the same problem with my 97 5.7L, and a reliable mechanic told me to check the ignition coil.  Sure enough it is cracked and I can see where it has been cross-arcing. I have new parts from ACdelco on hand, just trying to find time to replace it and see if that improves things. 

I'll check that when I get home later. That would be easier than taking apart the intake manifold.

[bcrooms]

Sadly, I replaced my coil....issue still there.  The mechanic that gave me the advice looked into the problem further and he suspects a bad fuel injector as the truck only does this at certain load and when the engine is wanting more fuel....Gonna try some fuel treatment to see if the injector is stuck....if the problem persists.....it will be new injectors and pressure regulator.  Seems to be a common issue on these engines

[riverbanks]

You are planning to do lower intake gasket also?while you're there

[Hillwood]

Sadly, I replaced my coil....issue still there.  The mechanic that gave me the advice looked into the problem further and he suspects a bad fuel injector as the truck only does this at certain load and when the engine is wanting more fuel....Gonna try some fuel treatment to see if the injector is stuck....if the problem persists.....it will be new injectors and pressure regulator.  Seems to be a common issue on these engines

You can pull the upper intake and pull all the injector lines out so you can see the nozzles.. Reconnect the fuel lines and crank it over to see which one is not spraying.

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