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Surging and backfiring

B

bobecke

New member
"On the first trip out after s

"On the first trip out after sitting the winter, my motor will backfire or cough and and surge a little bit when I increase the RPM's to 2500 and above. It starts OK and seems to run fine under 2000 to 2500. Motor is 95 5.7 alpha 1, 40 hrs. since new long block.

Would appreciate any thoughts before I have to take it in to the mechanic."
 
"Grab some carb cleaner and cl

"Grab some carb cleaner and clean the choke mechanism. It could be sticking. Now is a good time to clean the flame arrestor too. Then shoot the linkages and the butterfly valves on the carb.
The choke pulloff is often vacuum operated. Ensure that the vacuum line is attached to the base of the carb and is not cracked. In the worst cases, the choke pulloff diaphram is rotted requiring replacement of that small component.
Just some idea starters..."
 
Bob.
This could be fuel relat

Bob.
This could be fuel related but you may want to check the condition of the spark plug wires and check under the disributor cap for any water. Almost sounds like crossfire is going on. It may have water in the fuel but this would show up more at idle I would think. Hope you find the cause.
 
"Sounds like choke issues. Doe

"Sounds like choke issues. Does the running problem go away when warmed up? Are you getting black/gray smoke when experiencing the running problem?

If so, manually open the choke butterfly and see if it clears up. If so, you have choke pull off challenges or choke heater issues. Lets start by getting a solid diagnosis."
 
Will it run above 2500 rpm or

Will it run above 2500 rpm or is 2500 the most rpm you can get out of it?
 
"Yes Greenly, it will go right

"Yes Greenly, it will go right up to higher RPM's but then it's backfiring or coughing more so I don't push it. I don't try to check maximum RPM's because I'm afraid of wrecking something."
 
Update. Problem appears to be

Update. Problem appears to be solved. I changed all filters (no water). #2 cylinder wasn't firing well. Changed cap and rotor and plugs and it runs fine. Thanks for the help. Great forum!
 
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