Rough running under load.

[AltonR]

1985 Chevy 350 idles fine but under load misses and back fires. Have reset time and adjusted carburator. Carb recently overhalled and electronic ignition installed. What is the most likely cause and what can be done? Thanks! Rich

 

[Gary H NC]

Re: Rough running under load.

Did this problem start when the electronic ignition was installed? If so i would go back over that first.
Also could be bad fuel or water seperator filter needing replaced.

Just a couple possibilities..

 

[beermunk]

Re: Rough running under load.

1985 Chevy 350 idles fine but under load misses and back fires. Have reset time and adjusted carburator. Carb recently overhalled and electronic ignition installed. What is the most likely cause and what can be done? Thanks! Rich

Check your plugs.

 

[mark1905]

Re: Rough running under load.

Re-check timing.

 

[Bondo]

Re: Rough running under load.

Also could be bad fuel or water seperator filter needing replaced.

Ayuh,... Sounds like a Fuel Delivery Issue to Me....

 

[AltonR]

Re: Rough running under load.

Thanks guys! Plugs were recently changed during tune up. I Just drained the fuel and will replace the fuel and water separator as suggested along with new gas and a can of Sea Foam. Checked timing 3 times & idles best at 12 degrees before top dead center. Specs say 10 degrees. Am I too far off at 12?

 

[Don S]

Re: Rough running under load.

Kind of a waste to replace your gas. Don't just change the fuel filter, dump it out into a clear container and LOOK for water. If there isn't any water, it won't help much to throw all the fuel away. Besides, if there is a lot of water in it, there is an easy way to get the water out and save the fuel.

Does your advance timing work?

 

[AltonR]

Re: Rough running under load.

Don, thanks I'll check the advance again but when I have the timing light on and rev the engine the timing mark moves. I think that means the distributor is advancing the spark. I drained the gas and used it in my truck. No problems in the truck so fuel may not be the problem. It got dark before I could pull the water separator. I'll check it for water tomorrow. Rich

 

[J JACKSON]

Re: Rough running under load.

could possibly be a lobe worn off the cam too if you don't find anything on the carb pull the valve covers and spin it over to make sure all the rockers move

 

[bigskiohio]

Re: Rough running under load.

Missing under load is a indicator for bad spark plug wires sometimes or a bad spark plug , not enough spark to fire under pressure.