Runs then when it sits a idle eventually it’s loses spark

[vizionwolf]

So the truck has a different motor in it now it is a 350 vortec still just came out of another truck that had no issue. It now will only runs for about 20 mins from cold to idle temp and starts backfiring really bad and eventually dies seems like low spark the only differences is has open headers and spark plug wires gonna swap those tomorrow any insight will be helpful

 

[Erik the Awful]

Check your fuel pressure.

Make sure there's a thin film of thermal paste between your ignition module and where it mounts on the distributor. Without it your ignition module can't dissipate heat and will die out.

 

[Schurkey]

it is a 350 vortec... ...It now will only runs for about 20 mins from cold to idle temp and starts backfiring really bad and eventually dies

Connect a scan tool. Verify ALL the sensors especially the coolant temp sensor, and the crankshaft position sensor. Make sure the RPM signal does not drop-out.

Verify ALL the computer outputs, especially the IAC.

Look at the misfire counts per cylinder, and verify fuel trims.

The distributor cap is suspect. The United Motor Products cap which is vented has gotten positive reviews here.

Test the spark power using a spark-tester calibrated for HEI. There's many different styles. Avoid the ones that have a light-bulb that glows. You want to SEE the spark jump a calibrated gap.

My favorite kind of spark-tester:
www.amazon.com/dp/B003WZXAWK/?coliid=I3S98D7T1J0RLJ&colid=2VLYZKC3HBBDO&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

xc_hide_links_from_guests_guests_error_hide_media

Check your fuel pressure.

Yes.

 

[vizionwolf]

So has good fuel pressure even when it starts to die reads 55-60 replaced cam sensor truck runs longer than it did before but just does this about ten mins later than before when it dies it seems like the spark is weak

 

[Schurkey]

You were told how to test the spark power.

 

[vizionwolf]

I did test it to my knowledge it seems weak

 

[Schurkey]

HOW and WHERE did you "test" it? Did you use a spark-tester with a spark-gap calibrated for HEI? Did you test right at the coil, or downstream somewhere--where a burnt coil wire, failing cap or rotor, or failing plug wires could steal voltage?

Was the coil hot--like just after the engine stalled?

Even better--Did you mist the top of the coil with water from a squirt-bottle to verify the case of the coil isn't cracked or carbon-tracked?

What is the resistance of the primary winding? What is the resistance of the secondary winding? Does either winding have high-resistance continuity to ground? An ohmmeter can verify a defective coil, but it can't tell you a coil is good.

IF (big IF) the spark truly is weak at the coil, you need to verify the power getting to the coil, the wire harness between coil and ignition module, and if those are good...replace the coil.

 

[vizionwolf]

Did not use a spark plug tester won’t have it for a little so just ended getting a good ground for it and the distributor cap rotor wires and plugs are all new the coil was not hot to touch at all and when seeing if it’s cracked or carbon tracked what will it do if it does. One thing I noticed it does when it starts failing is on the scanner the spark advance goes from 15-30 repeatedly one theory I’m working on is the passenger header is pointing in the trans direction was wondering if it could be overheating the wiring for the cam sensor or anything.