Runs rough when accelerating

[Bandit130]

Engine started running rough this last week on accelerating. Runs normal in Park or Neutral while revving. Runs rough in gear sitting still also. Replaced plugs and the in-carb fuel filter today and no difference. Truck died on the street last weekend and I found a vaccuum hose had split on the end and fell off. Trying to restart I flooded carb and could not start for a while. This flooding may have caused an issue in the carb. The last rebuild was July 2017. Thinking I may need to rebuild again, not sure.

Any help is appreciated.

[4u2nv]

Maybe check the float ????????

[Corts60]

Put a vacuum gauge on it and see what you are pulling. If you have a stock-ish cam, you should be at least 16-18" vacuum at idle.

Other than that, you could have a weak fuel pump if fuel isn't keeping up under load.

[Dead Parrot]

Check all the suction rubber on the fuel system. Frame to pump. Valve to frame(if dual tank). Tank to valve(or frame if single tank). A hole in one of the hoses can cause the symptoms you have. If one hose was bad, possible others are as well. Also, mice will sometimes nibble on hoses.

A none fuel cause might be a bad distributor cap. There is a carbon button in the top of the cap that does wear out.

[Bandit130]

I have rechecked all vacuum lines, plug wires and all are good. Pulled dist cap and nothing bad found. Checked fuel lines and cannot find anything I can tell that is causing this. Would a bad ignition module cause this or possibly coil? I have had a no start due to the module before.

[Nick_R_23]

How have you checked the spark plug wires to determine if they are good? A miss under load is a common effect of an ignition problem. I would recommend replacing the wires, cap, and rotor with quality parts to eliminate that as a potential issue.

I would also take a look at your accelerator pump in the carb, and ensure it is working correctly.

[truckin 79]

I would say you still have some carbon/junk between needle and seat in carb. Put some carb cleaner through vent tube in carb should clean it up. Just trying to start truck should not cause truck to flood. If carb cleaner does not clear it up then you might have to take carb apart and clean

[Bandit130]

UPDATE

I performed all the troubleshooting I could do with only having a carport and limited tools. Finally decided to take it to my tech and said my cam had finally worn down that is causing the rough running. He had discovered the #8 cam lobe was worn a few years ago when replacing the valve stem seals. It was worn and only raising rocker arm a little. He is in the process replacing cam. He is going to put in an Edelbrock Performer cam. He said it is the beefiest he could install without any other upgrades which is more than the stock one. Should be finished by next Friday.

[geezer#99]

Considering all the fine metal dispersed inside your motor, a cam change is a waste of money.
There’s only one cure.
Complete tear down and cleaning.

[Bandit130]

I got the truck in 2015 and it has apparently been wearing slowly over the years so I think the metal has gone thru the filter and out with the regular oil changes that have been done since I have had it. I think it will be ok. Shall see.

[geezer#99]

Ya!
It’s only money!

[Nick_R_23]

I wouldn't take the chance on it. That metal tends to hide in the journals of the cam bearings and internal oil passage plugs. With todays detergent oils, it's likely those metal shavings can become dislodged and find their way around. Cams wipe lobes quickly and then work harden, so this isn't an issue that has been going on for years.

[cadillac_al]

I can't even count the number of worn 305/350 cams I have replaced without tearing down the engine. The shop I used to hang out at in the 70's used to just remove and replace them too. The oil filter must work. A full tear down is always better if you have the time and money for the peace of mind. If it's just an old truck, send it. MY 76 K15 is on it's 3rd cam at 180k miles.