Vortec 5.7 stumbles and backfires without giving and check engine codes

[LilWee247]

My pressure has shown 62 ever since I put it together. Still shows 62

 

[Schurkey]

Vortec 5.7 from 1998 K2500. now it stumbles and backfires with low power. No check engine light or codes.
Fuel pressure looks fine. New fuel. Put scan tool on and watched live data for O2 sensors and they appear fine.

How about all the other sensors? Verify EVERY sensor, verify computer outputs--timing advance, etc.

Don't look for misfire "codes", look at misfire counts for each cylinder.

Not likely! Start with a good cap and rotor. They are known to burn through internally and crossfire even though they look ok externally. I personally have had the best luck with MSD with brass terminals. The aluminum terminal factory ones are a terrible piece. Aluminum is a poor conductor and it overheats the insulating material, breaking it down.

Aluminum is an excellent conductor, better than brass. Aluminum is used for electrical wiring when copper is too expensive--for example, the 50,000 volt high-tension power cables that go across the country.

The issue is that aluminum is more-likely to build up corrosion where the arc jumps from the rotor tip.

The Vortec caps are particularly succeptible to cross-fire, due to having the high-voltage pathways crossing each other inside the molded-plastic of the cap.

 

[LilWee247]

How about all the other sensors? Verify EVERY sensor, verify computer outputs--timing advance, etc.

Don't look for misfire "codes", look at misfire counts for each cylinder.


Aluminum is an excellent conductor, better than brass. Aluminum is used for electrical wiring when copper is too expensive--for example, the 50,000 volt high-tension power cables that go across the country.

The issue is that aluminum is more-likely to build up corrosion where the arc jumps from the rotor tip.

The Vortec caps are particularly succeptible to cross-fire, due to having the high-voltage pathways crossing each other inside the molded-plastic of the cap.

I'm not sure that my code reader can see individual misfires. It did tell me a specific cylinder when I burned through a spark plug wire.

 

[Schurkey]

Don't use a "code reader". Use a real scan tool.

 

[LilWee247]

Don't have access to one.
My code reader has some live data usage.

 

[L31MaxExpress]

How about all the other sensors? Verify EVERY sensor, verify computer outputs--timing advance, etc.

Don't look for misfire "codes", look at misfire counts for each cylinder.


Aluminum is an excellent conductor, better than brass. Aluminum is used for electrical wiring when copper is too expensive--for example, the 50,000 volt high-tension power cables that go across the country.

The issue is that aluminum is more-likely to build up corrosion where the arc jumps from the rotor tip.

The Vortec caps are particularly succeptible to cross-fire, due to having the high-voltage pathways crossing each other inside the molded-plastic of the cap.

Exactly aluminum oxidizes, becomes a poor conducter, gets hot and causes stuff to melt. Had a house completely rewired to rid it of alumimum wiring before it burned to the ground.

The aluminum oxidizes on the end, the spark starts jumping back to un-oxidized aluminum that has less resistance, until eventually it burns into the cap and starts arcing up in between the cap material and the aluminum. The cap keeps melting away internally more and more until it fails.

 

[Schurkey]

Don't have access to one.
My code reader has some live data usage.

Which is the better option for you?
Get a usable scan tool system, or take it to a professional?

 

[LilWee247]

Which is the better option for you?
Get a usable scan tool system, or take it to a professional?

I was hoping to get some things to try before sending it to the shop. Definitely not opposed to sending to my favorite shop but they only get stuff from me if I can't figure it out. If it would just give me a code as a starting spot, I would probably have figured it out. I am pretty decent at general stuff but this one I just don't know where to start.

 

[Schurkey]

"Codes" can be helpful.

The real clues are in the data stream. Sensor data, misfire data, computer-output data, etc. Not to mention the bi-directional testing. And that requires a scan tool.

But in the meantime...have you pulled the plugs, and performed a cranking compression test? Have you checked resistance on your plug wires? Verified coil output using a spark-tester calibrated for HEI? Checked for failed intake gaskets? (That was a big problem years ago. Not so much now--but it still happens.) What is the voltage at the fuses that power the ECM?

 

[LilWee247]

I will check again to see what live data my reader will show. But you are talking about several things Idk how to do or even what tools to use to accomplish those tests.