94 chevy 350 needs some help

[chevy_29]

I have a 94 chevy4x4 350 automatic. I left the house this morning to go pick up some stuff with a 16 ft trailer. I stopped and put some gas in and went maybe 15 miles or so and all the sudden it started back firing and throwing flame out the exhause. It would idle fine even in gear but as soon as i touched the gas it would start back firing again. If i kept giving it gas it would die. I idled half way home or so. I tried hiting the gas again 20-30 min later and its fine. Right before it started back firing i was crossing some bridges with water puddles on it hiting them. After that it started. Before all this it has been fine with no problems. I have been hauling scrap loads off for a couple weeks and no problem til now. Could i have a cracked distributor or somthing or maybe water in gas? I dont know what really to check. Its running fine now. Also i have been hearing alot of synthetic oil and trans fluid. On this truck would it be better to switch to synthetic for both? If so what kind and size for motor and trans? I also have a 03 trailblazer. Would it be good to switch it over as well? The truck has 227,000 miles and the trailblazer has 130,000. I use 5-30 in the trailblazer and 10-30 in the truck. Any help on all this would be appreciated. Thanks in advance.

[Schurkey]

Originally Posted by chevy_29

I have a 94 chevy4x4 350 automatic. I left the house this morning to go pick up some stuff with a 16 ft trailer. I stopped and put some gas in and went maybe 15 miles or so and all the sudden it started back firing and throwing flame out the exhause. It would idle fine even in gear but as soon as i touched the gas it would start back firing again. If i kept giving it gas it would die. I idled half way home or so. I tried hiting the gas again 20-30 min later and its fine. Right before it started back firing i was crossing some bridges with water puddles on it hiting them. After that it started. Before all this it has been fine with no problems. I have been hauling scrap loads off for a couple weeks and no problem til now. Could i have a cracked distributor or somthing or maybe water in gas? I dont know what really to check. Its running fine now.

There are so many possibilities. You've covered most of them.

Contaminated fuel
Defective fuel pump
Defective distributor cap including the carbon button in the center
Defective distributor pick-up coil 'n' magnet
Water spray on defective plug wires
Water spray on defective fuel pump wiring
Water spray on defective engine sensors or actuators

There's probably other stuff as well.

The only way you're going to know is to start taking stuff apart for inspection. I'd start with ignition items, and then move to the fuel filter. If you can oscilloscope test the fuel pump as you check the pressure, that'd be wonderful. Otherwise a plain ol' ordinary fuel pressure test.

Originally Posted by chevy_29

Also i have been hearing alot of synthetic oil and trans fluid. On this truck would it be better to switch to synthetic for both? If so what kind and size for motor and trans? I also have a 03 trailblazer. Would it be good to switch it over as well? The truck has 227,000 miles and the trailblazer has 130,000. I use 5-30 in the trailblazer and 10-30 in the truck. Any help on all this would be appreciated. Thanks in advance.

Whatever viscosity the owner's manual recommends. I use synthetic in every engine I care about...but I also do oil sampling to determine the "REAL" drain intervals needed. I dump oil between 6K and 14K miles, depending on the vehicle.

Haven't played with synthetic trans fluid. Don't see the point--my vehicles go 100K between trans fluid changes as-is.

[j cAT]

Originally Posted by chevy_29

I have a 94 chevy4x4 350 automatic. I left the house this morning to go pick up some stuff with a 16 ft trailer. I stopped and put some gas in and went maybe 15 miles or so and all the sudden it started back firing and throwing flame out the exhause. It would idle fine even in gear but as soon as i touched the gas it would start back firing again. If i kept giving it gas it would die. I idled half way home or so. I tried hiting the gas again 20-30 min later and its fine. Right before it started back firing i was crossing some bridges with water puddles on it hiting them. After that it started. Before all this it has been fine with no problems. I have been hauling scrap loads off for a couple weeks and no problem til now. Could i have a cracked distributor or somthing or maybe water in gas? I dont know what really to check. Its running fine now. Also i have been hearing alot of synthetic oil and trans fluid. On this truck would it be better to switch to synthetic for both? If so what kind and size for motor and trans? I also have a 03 trailblazer. Would it be good to switch it over as well? The truck has 227,000 miles and the trailblazer has 130,000. I use 5-30 in the trailblazer and 10-30 in the truck. Any help on all this would be appreciated. Thanks in advance.

I would check the distributor cap/rotor/plug wires. measure resistance of the plug wires. check for cracks heat damage insulation and proper support hardware so wires are properly secured.

sounds like wires arcing over to each other..could also be inside the cap.

with the newer vehicle I would switch to synthetic fluids in the transmission you now use dexronVI this is synthetic as the new GM spec replaces the now droped dexronIII which should no longer be used.

with using a vehicle hauling replacement of drivetrain fluids all is usually done more frequently ..most with this type of use replace the fluid every 15-30,ooomiles.

I would stick with the 10-30wt dino oil in the 94 truck..the 2003 trailblazer should be on 5-30wt synthetic...