Lionhearted5.3

Motor:
5.3L
LS9 Cam, LS3 Springs, LS7 Lifters,LS6 intake/throttle body, Etc, Tuned

Car ran fine (very rarely it would pop when you tried to start it) until I replaced the Oil pan and valve covers.

It started and idled just fine until it warmed up and then it made a random shotgun backfire and then another so i shut it off. Tried to restart it and now it pops, backfires thru intake and will eventually start, but backfire like a shotgun after idling.

Replaced:
Crankshaft Position Sensor (3 times)
Camshaft Position Sensor
Double checked wiring on Coils as they were removed for the valve covers


What could I be missing? Im pulling my hair out. Please help.

JoeNova

Triple check coils. Unplug and plug back in each one and the main connector.
Check to make sure the coil grounds are still in place.
If you managed to swap coil connectors from coil to coil or even side to side, this will happen.

Lionhearted5.3

Admin never approved my reply.

But it I figured it out! Thanks for the help!

Coil pack connector on the passenger side is pinned wrong. I actually had to swap all the coil pack wiring just on that side.

Its alive and a beast again!

Kevin Bearss

I had the same problem did the plug change coil pack changed everything you did and rechecked my wiring to coil packs and turns out there are 2 grounds on for each side of coil packs the drivers side wasn't ground causing the back fires engine run on and the inability to idle without idle acting clean at first then idle lowers and misses then cleans up then back to missing and idle low and timing curve in mid 6014 doesn't help and will make it worse so check your coil pack grounds their is 2 one on each side

gets70

If it backfired it could be a possibility that it jumped time if its a high miles engine?? Just a thought. Had a SBC do that.