1983 C10 305 mind boggling engine problem

[thomps92]

Hello, This is my first post. I am at my wits end. I have a 1983 C10 with 100,000 miles on it. For the last few months the truck has run like a piece of garbage. The main symptoms are that it starts seemingly well, but I will drive it for about 10-30 miles and then all of a sudden the engine will bog down, it won't downshift softly and then the engine temp gauge starts to rise to about 210-230 degress. Sometimes the problem goes away and other times it won't. But all the while the engine has very little power and wont accelerate even with the pedal on the floor. Most of the time during these episodes when depressing gas pedal fully the engine will spit and sputter and have very little accelerating power. Just installed new cap and rotor which made it idle alot better and initially helped truck respond better, but the main problem still exists with the bogging/shifting/overheating problem after 10-30 miles. temp gauge reads normal up to this point. I am thinking I should replace the entire distributor, but want to rule out other problems. There are no vacuum leaks. Any ideas? Thanks guys.

[Dead Parrot]

Carb or TBI? Computer? Emission stuff still there or pulled off? A couple of things to check. Battery and alternator connections. And distributor power. The fact that the problem starts suddenly could be a loose wire somewhere. If computer, check those connections as well. Check the coolant level and maybe replace the thermostat since the temp gauge goes up when the problem starts. Could be a nearly plugged fuel filter. Are the engine block grounds good?

[legendman]

Do you have the stock air cleaner still on it? I found a mouse nest in the tube going from the radiator support to the air cleaner, completely blocked off.

[thomps92]

It is a carb (quadrajet) and as many vacuum lines disconnected from unneccessary things as possible. There are no vacuum leaks and truck has run fine before with vacuum lines unhooked and blocked off. Also, truck has headers and no catalytic converters. Aftermarket aircleaner, brand new fuel filter. Thanks

[68longhorn]

does your distributor have 4 extra wires coming out of it? My 86 has that and the computer would randomly retard timing and do all that. I can't remember what 2 wires, but 2 need to be wired together, or you can put in a traditional dizzy.

[y5mgisi]

Im betting ignition module.

[Axle]

Pull the airhorn off the carb and look for black specks in the float bowl.
If you find those, pull the accelerator piston, remove the screw at the bottom, pull the checkball, blow carb cleaner throught the passage, put it all back together.
Then plug the vacuum line between the carb and the chaarcol canister.

Alex.

[motornut]

hmmm
kinda sounds a bit like what i just worked through in the 79
replaced cracked rubber bits in gas lines
sending unit was leaking started to smell it,could see 1/4 return spitting fuel over tank
dark shot taken while in truck
rock wedged in the lines lol

fuel pump?

headers so no heat riser or cat to plug....

choke work ok?

as mentioned that line to the canaster,3/8? mine had a big crack on the bottom seam,
couldn't see it from the top,felt it when squeezing the hose tho

[Slonaker]

I don't know if this will help, but I once had an Oldsmobile with an HEI that would do that. It had a broken wire on the pickup coil. When the vacuum advance would do its thing, the wire would bend at the break and the engine would bog badly. Let up, and it was fine.

As long as I drove it with the vacuum line disconnected it would run fine, but didn't have as much power as it should. You could always disconnect the vacuum line next time to test for that...

Slonaker

[Theweatherman]

I am having a very similar problem. I think that my issue is clogged catalytic converter. I will post back after get a chance to cut out the cat to take a look but I wanted to know if you had ever diagnosed the issue you were having.

Thanks,

Ross

[68longhorn]

weatherman, what year is yours? is the issue constant or comes and goes? I've never seen a cat only sometimes cause issues.

[Theweatherman]

It is a 1983 305 engine with 2 barrel carburetor. The truck never goes over 20 miles per hour as it is a ranch vehicle. I started to notice a loss of power about a month ago and it would range from no problems to a severe bog down, requiring full throttle to climb slight inclines.

As of yesterday the problem is constant the engine will rev when in neutral but under a load it always bogs down. I checked all the spark plugs everyone one is wet fouled but sparking like the engine is running rich.

The water temperature runs around 225F constantly after the initial warm up period.

The air filer is clean.

The carb is clean with both jets functioning properly.

When I get back out to the ranch I am planning on cutting out the CC and replacing the 18" section with 2.5" flex tubing to see if this fixes the problem.

[motornut]

I'd check the choke and wire it off to confirm it's not an issue
check the vacume advance under the rotor,make sure the weights move ok and the pivot holes for them are not oblonged
sometimes pulling off those small hoses loosens the small tubes going into the carb
a slight tap will reseat them...
farm truck eh? how do you get your gas? filter ok?
I've seen rusty junk stuck between the block pump and carb,drained out the line there to a cup,after evap I found almost a rusty sand sediment floating around...
as recently as this spring a new issue,the back flow valve if the fuel filter was getting sucked threw the line blocking the gas flow....I removed the valve

any pics of setup?

[mrolds88]

Sounds like its running lean to me. I would check the pick up in the tank. 30 year old truck, work vehicle could have collected enough rust/ dirt over the years to finally plug the thing enough. You can check the pump output by disconnecting the HEI wire and the fuel line at the carb and give it a crank to see how output is.

[willett]

I have had intermittent power with a clogged fuel filter before. Spend the $10 and replace it!

[68longhorn]

could be fuel filter. Don't know if 2 barrels had the ESC module, but look on the distributor for 4 wires coming out of the back, unplug the connector and jump I believe the green and black wires together on the distributor side. Then drive around and see how it is