Vortec 5.7 sounds 180 degrees out of time

[A-Z Auto]

Anyone ever see this issue? I have a 92 c1500 that I did a complete swap to a 99 Tahoe 5.7 vortec... harness & all over a year ago & no problems. It was running perfect yesterday & today I get in & try to start it & it sounds like it’s 180 degrees out of time. Any ideas would be greatly appreciated... I did check all fuses & it will connect to my scanner... but gives an error when trying to pull codes

 

[Crazydavez28]

If it is backfiring and chugging gas vapours out of the exhaust my high mileage 300k Vortec motor does this anytime it rains or is humid. I'm not sure what it is that causes it but changing the crank sensor did me zero good.

Once she decides to run it runs perfect like nothing happened.

I think it might have to do with increased blowby and the moisture finds its way into the distributor thru the worn bushings.

 

[Jeffro87]

Failing coil, or you have contamination in distributor, is it pulling oil up into cap?

 

[Oldblue98]

When mine did that it was crank sensor, went to bang it off one day sitting at gas pumps kicked back and then starter just would grind, had it towed . When I got home and went under it, when it backfired and kicked back it broke starter housing and took out Flex plate teeth. But while trans was out I had trans rebuilt and new flex and new starter and new crank sensor.. Knock on wood it has never done it again. Distributor is first place I would go and check out for sure. I am under the understanding the cap and rotor can be problematic as well on Vortec.

 

[A-Z Auto]

I’ll check the distributor next. I was just really confused bc it’s been running like a top... the distributor is new but a rock auto cheap replacement

 

[Oldblue98]

I’ll check the distributor next. I was just really confused bc it’s been running like a top... the distributor is new but a rock auto cheap replacement

Check screws on cap & rotor seems as I have read about screws backing out .

 

[A-Z Auto]

Update!! Got it to start & connect to my scanner... not really sure what I did other than putting the battery on charge overnight. Either way... it’s running again. Thanks y’all

 

[Justin S]

I had a similar issue today and not sure if I actually fixed it. I've had a p1345 for a while but it would still start. This morning it would only sputter. I know it shouldn't be the crank sensor since it at least tried to fire, it would sound like it was going to catch, then backfire out the exhaust. I tried a cap and rotor and it didn't change anything, but then swapped plugs since they were fouled and it fired right up, so I don't know. I made sure i had power to all the sensors. I probably need a distributor anyways still.

 

[Supercharged111]

I had a similar issue today and not sure if I actually fixed it. I've had a p1345 for a while but it would still start. This morning it would only sputter. I know it shouldn't be the crank sensor since it at least tried to fire, it would sound like it was going to catch, then backfire out the exhaust. I tried a cap and rotor and it didn't change anything, but then swapped plugs since they were fouled and it fired right up, so I don't know. I made sure i had power to all the sensors. I probably need a distributor anyways still.

Every time I swap an engine I swear that ****** NEVER fires on its old plugs regardless of my determination. A plow truck would totally pull this crap too with all it's short run cycles and lack of highway miles to really clean things out. OP is this a seldom driven engine or did you keep the plugs from the swap?